The Bottle Builder 1

A COMPENDIUM OF TUBE AMP DESIGNS

THE BOTTLE BUILDER VOLUME 1

Johan Basse Bergqvist LEARN

DESIGN

SHARE

RE ● LEARN ● DESIGN ● SHARE ● LEARN ● DESIGN ● SHARE ● LEARN ● DESIGN ● SHARE ● LEARN ● DESIGN ● SHARE ● LEARN ● DESIGN ● SHARE ● LEARN ● DESIGN ● SHA ARN ● DESIGN ● SHARE ● LEARN ● DESIGN ● SHARE ● LEARN ● DESIGN ● SHARE ● LEARN ● DESIGN ● SHARE ● LEARN ● DESIGN ● SHARE ● LEARN ● DESIGN ● SHARE ● L DESIGN ● SHARE ● LEARN ● DESIGN ● SHARE ● LEARN ● DESIGN ● SHARE ● LEARN ● DESIGN ● SHARE ● LEARN ● DESIGN ● SHARE ● LEARN ● DESIGN ● SHARE ● LEARN ● RE ● LEARN ● DESIGN ● SHARE ● LEARN ● DESIGN ● SHARE ● LEARN ● DESIGN ● SHARE ● LEARN ● DESIGN ● SHARE ● LEARN ● DESIGN ● SHARE ● LEARN ● DESIGN ● SH EARN ● DESIGN ● SHARE ● LEARN ● DESIGN ● SHARE ● LEARN ● DESIGN ● SHARE ● LEARN ● DESIGN ● SHARE ● LEARN ● DESIGN ● SHARE ● LEARN ● DESIGN ● SHARE ● RE ● LEARN ● DESIGN ● SHARE ● LEARN ● DESIGN ● SHARE ● LEARN ● DESIGN ● SHARE ● LEARN ● DESIGN ● SHARE ● LEARN ● DESIGN ● SHARE ● LEARN ● DESIGN ● SHA ARN ● DESIGN ● SHARE ● LEARN ● DESIGN ● SHARE ● LEARN ● DESIGN ● SHARE ● LEARN ● DESIGN ● SHARE ● LEARN ● DESIGN ● SHARE ● LEARN ● DESIGN ● SHARE ● L

Table of Contents

Table of Contents Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15 About the Designs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17 Conventions used in this book . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18 The Hype . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18 The Real McCoy . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20 Choice of Components . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22 Good Practices . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24 Heater Wiring . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25 Ground loops . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25 Hazards . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25 Disclaimer . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26

1. BLUBOTTLE – small amp, big sound . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27 General circuit description (left channel referenced) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27 The Tone Control . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28 The Phono Stage . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28 Coupling capacitors . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29 Indicator Tubes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29 The Power Supply . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29 Building and Tuning . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 30 Powering up for the first time . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 32 Problems . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 32 Maintenance . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 32 Chassis mounting . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 32 Bill of Materials . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 33

2. Octopus, the Octal lover’s 2 x 8W integrated amplifier with MS option . . . . . . . . . . . . . 47 The tone control . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 47 Volume and balance controls . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 48 The space in between . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 48 The Power Amplifier . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 49 The driver stage . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 50 To NFB or not to NFB – that’s the question . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 50 Building Octopus . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 50 An MS Speaker System . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 51 Speaker Connectivity . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 51 PCB Bill of Materials . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 52

3. SBS: Side by Side dual beam tetrode SE power amplifier . . . . . . . . . . . . . . . . . . . . . . 65 The circuit . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 65 Back to the circuit . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 66 Bias settings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 66 Regulated screen grid and preamp/driver supply . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 67 The Power Supply . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 67 The Output Transformer . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 67 Ultra Linear SE output transformers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 68 PCB versus tag board . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 68

4. Caviar – Nerd class-a in a bay . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 71 The Caviar amp . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 71 The Power Supply . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 72 Practical Design . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 72 Assembly . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 73

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The Bottle Builder: A Compendium of Tube Amp Designs vol. 1 5. Lightning – Extremist 2 x 24W triode class-A SE with 812A power triode . . . . . . . . . . . . 81 General . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 81 Triode Technical Issues . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 82 The Preamp . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 82 Driver Stage . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 83 Output Transformers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 84 The Power Supply . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 84 Driver Stage Supply . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 85 Preamp Tube Heater Supply . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 85 Driver Heater Supply . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 85 Power Tubes Heater Supply . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 86 Bells and Whistles . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 86 Performance . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 87 Firing the Lightning up for the first time . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 87 Printed Circuit Boards . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 88 Epilogue . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 89 Bill of Materials . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 89

6. Single Ended Channel amplifier with electronic cross-over . . . . . . . . . . . . . . . . . . . 101 The Concept . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 101 Treble Channel . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 101 Bass Channel . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 101 Preamp Tube . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 102 Magic Eye . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .102 The Power Supply . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .102 The Speaker . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .102 Visual Signal-to-Noise Ratio . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 103

7. WORKING MOJO – an approach to virtual damping factor . . . . . . . . . . . . . . . . . . . 105 The Amp . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .105 Damping Factor . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 105 The POWRTRON and Stanley F. White . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .106 The Circuit . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 106 The MOJO Working . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .108 The Driver Stage . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 108 The Output Stage . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .109 The Power Supply . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .109 Working the MOJO . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 110 The acid test goes like this: . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 110 The Tag Board . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 111 Printed Circuit Board . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 112 Bills of Material (BOM) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 113

8. A modular preamplifier . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 125 An Overview . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 125 Channel Amplification versus bi-amping . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .125 The main module . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .126 Electronic Crossover . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 127 The phono preamps . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 128 Regulated power Supply . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .129 Performance and considerations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .130 Bills of Material . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 131

9. Sterling Mixed mode/extended class-A 50W amplifier . . . . . . . . . . . . . . . . . . . . . . 147 The Circuit . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 148 It’s Miller time! . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .149 The Phase Splitter . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .149

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Table of Contents The preamp Stage . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .149 Power Supply and Negative Bias . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 150 The Screen Grid Voltage Regulator . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 151 Bias adjustments . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 151 Indicator Tube . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 151 Building the Amp . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 152 Measured Data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 152

10. Saturday Night Special output transformerless 2 x 25W power amplifier . . . . . . . . . . 157 The Circuit . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 157 Power Supply . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 158 The Power Stage . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .158 The Phase Splitter/driver . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .159 First Amplification Stage . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 159 Adjustment and connecting a transformer . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 160 Matching Transformers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 161 Building It . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 161 Heater Wiring . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .162 Grounding . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .162

11. Play Your Willie: The Williamson Amplifier – with a twist . . . . . . . . . . . . . . . . . . . 165 Is The Willy really a good amplifier then? . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .165 The Original Williamson Design . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .166 Was Willamson Wrong? . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .166 Was Williamson wrong then? . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .167 The Willie . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .168 The Voltage Amplifier . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .169 Alternative Driver Stages . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 170 The Output Stage . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .171 The CCS Explained . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .171 The Output Transformer . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 172 Switching Between Modes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .173 Switching On . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .173 The Power Supply . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .173 Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 174 Printed Circuit Driver Board . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 174 Cathode feedback . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 174 Adjustments . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .175 Bills of Material (BOM) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 175

12. HEADSUP Expensive Headphone Amplifier . . . . . . . . . . . . . . . . . . . . . . . . . . . 187 Crossfeed . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 187 The Main Circuit . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .189 The Driver Circuit . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 189 The Crossfeed Circuit . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 190 The Power Supply . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 191 Building Headsup . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 191 The connector board . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .192 Playing it . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .192 Bills of Material (BOM) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 192

13. RIAA and phono preamp stages . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 203 Phono preamps – a variation on a theme. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .203 A little bit of history . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 203 What is all this hue and cry about de-emphasis curves? . . . . . . . . . . . . . . . . . . . . . . . . . . . .203 The equalization curve . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .205 The Designs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .205

9

The Bottle Builder: A Compendium of Tube Amp Designs vol. 1 RIAA using Pentode and triode SQ tubes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 205 Performance and considerations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .206 - and now for something completely different: The KYO . . . . . . . . . . . . . . . . . . . . . . . . . . . 207 A first glance . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 207 The Circuit . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 208 Input selector . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .208 The amplifier stages . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 208 De-emphasis circuits . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .209 Power Supply . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 209 VU Meters . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 210 Performance and considerations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 210 OCTALS – a vintage tube RIAA preamp with shunt de-emphasis . . . . . . . . . . . . . . . . . . . . . . 211 The Circuit . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 211 Considerations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 212 Bills of Material (BOM) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 212

14. PURISTE – straight SRPP preamp with pentode passive-RIAA . . . . . . . . . . . . . . . . 229 General circuit description (components reference to left channel except where common). . . . . . . . 229 Tape Output . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .229 The Line Amplifier Stage . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 230 The Power Supply . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .230 The Choke L3 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .231 Heatsink . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .232 Capacitors in the power supply . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .232 High Voltage and supply . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .232 Practical build . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 232 Bills of Material (BOM) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 233

15. Q22: A QUAD 22 preamplifier clone . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 237 The Issues . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .238 The Circuit in General . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .239 Phono Preamp . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 240 Plug-In Adapters . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .240 Switching Circuits . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 241 DISC Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 242 Volume Control . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .242 Tape Output . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .242 Line Amplification stage, Tone Controls and Low-pass Filter . . . . . . . . . . . . . . . . . . . . . . . . .243 Tone Controls . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .243 Low-pass Filter . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .243 Power Amplifier Connection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .243 General Specifications . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .244 Switching Logic . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .245 Switch 1 and switch 10 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .245 20-pole header J1 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 245 The Power Supply . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .246 Bills of Material (BOM) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 247

16. STRAIGHT – a simple ultra low noise preamplifier . . . . . . . . . . . . . . . . . . . . . . . 263 The Circuit . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 263 The Tone Control . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .264 The Phono Amp Stage . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .264 The Power Supply . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .265 Setting Up . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .266 Practical Experience . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .266 Building The Straight . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 267 Cooling Fins . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .268

10

Table of Contents Input Switch . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .268 Performance . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .268 Bill of Materials . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .269

17. UNIDRIVE – a universal power tube driver with options . . . . . . . . . . . . . . . . . . . . 277 The UNIDRIVES . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .277 UNIDRIVE I . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 277 Heater Circuit . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .277 Printed Circuit Board . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 278 120W Amplifier . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .278 Adjustments . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .278 UNIDRIVE II . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .279 UNIDRIVE II 30W Ultralinear Amplifier . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 279 Stereo operation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 280 Bill of Materials . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .280

18. SUBSTORY – ultralinear PP 50W subwoofer amplifier with bass boost circuit . . . . . . . 287 The circuit . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .287 The Driver Stage . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 287 Phase Splitter . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .288 Preamp . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .288 Bass Booster . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .288 Power Supply . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 289 Negative Bias Supply . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .289 Layout . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .289

19. 3-way active crossover using miniature tubes . . . . . . . . . . . . . . . . . . . . . . . . . . . 291 The circuit . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .291 Schematics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .291 Building it . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .292 Adjustments . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .292 Bill of Materials . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .293

20. Variable active electronic crossover . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 299 21. LIBRA balanced preamplifier . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 301 What is a balanced amplifier… . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .301 Application for a phono cartridge . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 301 Amplifier noise . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .302 The Circuit . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 302 Mods for your turntable . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .302 The Attenuator . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 304 Conversion circuits . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .304 Now for the output stages – a true challenge . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 304 The Power Supply . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .305 Performance . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .305

22. A balanced power amplifier . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 313 The input stage . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 313

23. The Volutile ultimate physiological volume control . . . . . . . . . . . . . . . . . . . . . . . 315 Where are we going with all this? . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 315 Correct Setup . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 317

24. The Leak Tweak – case for beefing up a TL12+ . . . . . . . . . . . . . . . . . . . . . . . . . . 321 A virtual rectifier tube . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .322 More mods . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 323 Constant Current Cathode Contraption . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .323

11

The Bottle Builder: A Compendium of Tube Amp Designs vol. 1 Does it make a difference? . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .324 Bill of Materials . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .325

25. Leak Stereo-60 Clone 2 x 30W ultra linear amplifier . . . . . . . . . . . . . . . . . . . . . . 335 The Power Supply . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .335 The Amplifier . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .336 The Layout . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .337

26. Leak Point One preamplifier clone . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 339 Back to Point One . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 339 Is it worth building? . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 339

27. Microphone studio preamp with input attenuator . . . . . . . . . . . . . . . . . . . . . . . . 343 The Power Supply . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .343 Performance and considerations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .344 Construction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 344 Bills of Material (BOM) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 345

28. The Tube – a stereo condenser microphone . . . . . . . . . . . . . . . . . . . . . . . . . . . . 349 Back to business . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 350 Output Capacitor and Transformer . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 351 The Power Supply . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .352 A Printed Circuit Board . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .352 Performance . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .352

29. Conversion of Electret Microphones to Phantom-feed . . . . . . . . . . . . . . . . . . . . . . 357 About Electret . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .357 Electret Microphones . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 357 Building it . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .359 Performance . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .359 Converting a small asymmetrical electret mike to phantom feed . . . . . . . . . . . . . . . . . . . . . . 359

30. M/S stereo recording techniques . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 363 How to do M/S recordings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .363 What is actually happening here? . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 363 Practical Considerations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .364 M – the center microphone versus the S-mike . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 365 Recording . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .365

31. M/S to A-B decoder . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 367 Now for the smart part . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .367 Power Supply . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 368 Printed Circuit board . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 368 Bill of Materials . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .368

32. Line Level Stereo Compressor . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 373 What does a compressor do? . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 373 Types of Compressors . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 374 6HZ6 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .375 The Power Supply . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .376 Application . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 376 Printed Circuit board . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 376 Bill of Materials . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .376

33. Power supply for 8 vintage Neumann Microphones . . . . . . . . . . . . . . . . . . . . . . . 383 Practical Aspects . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .385

34. Power supply for a single Neumann vintage microphone . . . . . . . . . . . . . . . . . . . . 387 12

Table of Contents 35. The Shrimp – Personal Guitar Amplifier Illustrations: . . . . . . . . . . . . . . . . . . . . . 389 Amplifier Schematics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .389 The Reverb Unit . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .390 Power Amplifier . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .390 Power Supply . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .391 Building The Shrimp . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .391 Bill of Materials . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .392

36. The Mellow Yellow Studio Guitar Amplifier . . . . . . . . . . . . . . . . . . . . . . . . . . . . 399 The Mellow Yellow Knob . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .399 The Dual Gain Controls . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 400 The Reverb Circuit . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 400 The Tremolo circuit . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .400 Power Amp . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .400 The Power Supply . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .401 Adjustments . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .401 Choice of speaker . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .401 Box . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 402

37. The Gyratizer - 10-band parametric equalizer . . . . . . . . . . . . . . . . . . . . . . . . . . 405 What is a Gyrator? . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .405 The Circuit . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 405 Power Supply . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 406 Performance . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .406 Building The GYRATIZER . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .406

38. Continuo II – a compact 400W hybrid combo for upright bass . . . . . . . . . . . . . . . . 409 Background . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .409 The Bass Booster . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 411 The Mid Boost . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 411 The Compressor . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 411 The Equalizer . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .412 The Output Stage . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .413 Slide Potentiometers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .413 The Power Regulator . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .413 The Speaker and Enclosure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 414 Printed Circuit board . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 415 Adjustments . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .415 Hooking up to a power amplifier . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .415 Line Output . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 416 Bill of Materials . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 416

39. Capacitor Test Jig Illustrations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 425 40. Roadies Disgust – 300W RMS all tube bass amplifier . . . . . . . . . . . . . . . . . . . . . . 427 The Circuit . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .427 The power Amplifier . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 428 Line outputs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .429 The power Supply . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .429 The Preamplifier . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .430 Equalizer . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .430 Performance . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .431

Index . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 435

13

Introduction

Introduction I am an engineer, a performing musician and a HiFi aficionado as well as a keen builder of ‘things.’ All kinds of things from amplifiers and peripherals to complement them to large mechanical contraptions for sailing or driving somewhere, automation of curtains, building of guitars and computer controlled drainage pumps for my house.

Since my major was in microwave I spent half a year learning how to weld, solder, run a lathe, use NC machinery and do metal works in general. In my microwave world real men send power through square tubes so I guess I am a plumber too.

I hold several patents, mainly within telecommunications and have written countless articles in various magazines, lots of them aimed at the DIY crowd. I hunt for food (not for trophies), shoot handguns, collect firearms and old American cars (some vintage, some just old) and play all kinds of music in several bands from classical to rock. I understand neither the music nor the cultures of gangsta rap, graffiti and drive-bys. Maybe I will some day – I assume I must adjust to the music since it obviously refuses to adjust to me.

That is about it – apart from my lovely family including 5 grandchildren, who put up with me and dutifully laugh at my antiquated jokes.

Technology always fascinated me – all kinds of technology. At an early age my family noticed my knack for everything electrical and mechanical and donated outdated radio sets for me to play with.

These were the days of the tube or valve if you wish and I usually took the sets apart, trying to figure out how they worked and cleaned the components, straightened the wires saving the parts for a rainy day.

At the ripe age of nine – probably on the proverbial rainy day - I built my first super regenerative shortwave receiver from a description in Popular Mechanics on a crude plywood chassis and somehow managed not to kill myself in the process. I could not afford mains transformers, so everything was connected directly to the 220VAC mains, and to everybody’s surprise including my own: It worked. Sort of. I could receive Radio Luxembourg on 208 meters (the world’s first pop radio), which was the whole point. The other one was Voice of America Jazz Hour offering live transmissions from 52nd Street with people like Duke Ellington and Count Basie.

The solder joints were something to see – I only had an ancient gas-heated contraption for soldering drainpipes.

Subsequently my father in recognition of the accomplishment invested in my first real soldering iron + a Philips 12” 9760 full range speaker – and that was basically my introduction to proper soldering and upper level audio in one fell swoop.

The Philips speaker was excellent (I wish they still did stuff like that), so I put together an 8W push-pull amplifier using two x CL4 as power tubes – recovered spares from the radio sets. The output and mains transformers were both home made from re-wound chokes of which I had an ample supply harvested from the old radios.

To my amazement the sound quality of my home brew was far superior to anything I had previously heard from a radio when using the home brew PA amplifier/speaker with a turntable. The latter-day 78 RPM records were in fact High Fidelity or close enough (Capitol 78 RPM was real mono HiFi) and I heard things I never noticed before.

Sheer luck made me design the speaker cabinet just right even if I did not realize it at the time. Thiele & Small were not even born then…

The predominant design parameter was actually whether or not the speaker box would fit on my bicycle when I did gigs: This was my band’s PA system together with an ancient Bang & Olufsen dynamic microphone I ‘borrowed’ from my father’s wire sound recorder.

I guess my fate was sealed. Life to me was never the same since.

For my 14th birthday my sole wish was the then famous Mullard 5-10 10 W amplifier kit and a Lenco turntable. I got both and a new world opened to me. Avery Fisher, John Karlson and David Hafler were my gurus, not knocking my science teacher, who shared my interest and supported me with profound technical advice. Rest your soul, Mr. Broby, who understood my cravings, taught me the math and how to wind transformers.

15

The Bottle Builder: A Compendium of Tube Amp Designs vol. 1 After straying for years with transistor and power-MOS amplifiers I find myself back where I started. True HiFi aficionados persist in believing, that something important in vinyl grooves is lost during digitalization.

They just may be right. Life is after all analog.

The same aficionados (what we today would categorize as nerds) also persist in tube amplifiers subjectively sounding better than most solid-state amplifiers. This I can definitely confirm: They do. Tube amps have output transformers eating most of the unpleasant 3rd harmonic distortion, add a bit of 2nd harmonics and hence sound…nice.

One of the other reasons for today’s sweet tube-sound may well be, that contemporary tube amplifier designers employ only the very best components: The cost is outrageous anyway, so why not go the last mile – which is rarely the case when it comes to the crummy discount Chinese audio equipment we mostly encounter: The lowest common denominator.

They look like plastic, they smell like plastic and they sound like plastic too. However, back in the day we did see some really awful cheapo Japanese tube sets too, so tube amps are not necessarily better by default. It all depends.

In the day and age of MP3 who cares anyway?

Well, some of us still do.

My fellow musicians without exception go for tube amplifiers. Nothing else will do. Truth be told I am from a time – and so are my grizzly fellow performers – when The Silver Beatles were just back from Hamburg, so maybe it is simply a matter of taste and habit acquired over the years rather than objective listening.

However, my younger colleagues seem to agree with me and vintage VOX amps sell for the price of a car these days. Coming to think of it: Collecting VOX and Marshall amps would have been a much more rewarding investment than collecting shares and bonds. Unfortunately I did neither.

When you look at the circuit for a Fender Blues deVille or Super Twin Reverb amp the designs are pretty crude, but played together with a 1962 Fender Telecaster you have to admit: Yez! This is the sound. Only goes to show just how much your brain can change your perception.

The tone and pleasant distortion is exactly as it should be - or did we maybe just get accustomed to it? Guitar amplifiers in the 1960’s were built by ear rather than by design, I guess. I suspect Joe Piazza, responsible for a lot of the classic amps, was a musician with a knack for electronics rather than an engineer. Practically every manufacturer worth his salt has copied the Fender tone stack even if I still fail to understand why. It basically does not work but it does sound nice doing nothing – and maybe sounds nice for that very reason.

The designs you see in this book have been designed half by engineering and half by listening.

My engineering background, albeit not exactly in this field, may have kicked in occasionally, but first and foremost: As a musician I know how an orchestra and/or instrument is supposed to sound and as an engineer I know how to get it.

In the late 1970’s I commissioned and built the world’s first computer controlled theatre sound systems for The Royal Danish Theatre and Ballet in Copenhagen: Two immense sound systems basically conceived by Robin Bransbury (later co-inventor of Dolby Surround, life long friend and receiver of an Oscar Academy Award for his accomplishments) and a very young Anthony Waldron, now the grand old man of British studio engineering, both working for the British company Cadac of Luton at the time.

I count myself lucky for the inspiration and friendship extended by these esteemed gentlemen.

The systems were an unequivocal success. They were marvelous creatures but at least half of the success was due to the Royal Theatre’s management demanding, that all audio engineers should also be performing musicians with music reading skills too.

After all: If you don’t know what music is supposed to sound like how can you do a proper mix?

And right they were. How can you indeed? Sound systems are mere tools.

- which brings us back to the topic: This book was written by a dedicated HiFi-nerd-cum-musician-turnedengineer knowing (I believe) how an orchestra should sound.

16

Introduction The designs may not be perfect but each and every one satisfies my ear. Yours too, hopefully.

When building these designs you will find, that some components are expensive, especially transformers and power tubes – some may be rare but all are available. Nothing but the best will do and you shall be rewarded accordingly. In perfectionist audio there can be no half measures.

About the Designs This book had the working title ‘Class A,’ which does not necessarily imply, that all the designs employ class A output stages. Maybe the title should have been ‘1st Class’ since no effort has been spared to achieve the highest possible sound quality. None of circuits are particularly sophisticated: In my experience simple circuits perform better.

If you adhere to some basic rules, keep it simple and use the very best components you will end up with a highend product lasting a lifetime.

Be warned: You are about to embark upon an endeavour from which there is no return and you will soon be acquainted with the unit of measure known as a ‘WAL’ (Wife Acceptance Level) and of the phenomenon known as a ‘HUS’ (Horizontal Unused Space) – both rare commodities sparingly administered once you really get going.

From the first time you hear the sweet sound of your handiwork you will never stop reaching for even higher goals. Remember I told you so. Don’t come whining afterwards because you spent your life’s savings on an output transformer. We have all been there, done that and lied to our wives about the price.

According to Murphy’s Law on Activity your amplifier building will take up all available space in your dwellings. Should you move to a bigger place the same rule applies, just on an extended scale.

I have built all the designs over the years. My wife has patiently put up with the ever changing audio installations trying to figure what the knobs did until I bought an engraving mill and put some text to the front panels. After a while I could not remember what the knobs did either, you see.

Many builds were made presents of once finished, so in the process of writing this book I had to build some of them once more and hopefully managed to correct past mistakes. Building tube amplifiers is much like maintenance of a wooden ship: It never ends. It is.

The designs are hands-on: If you follow the instructions you can build and enjoy these designs. Some are suitable for beginners; others are more advanced and require more skill.

If this is your first home brew tube amplifier I recommend starting with one of the designs for which a Printed Circuit Board (PCB) is available. Tubes are in many ways more forgiving than semiconductors but a lot more critical when it comes to layout due to the high impedances and high voltages. Most tubes will happily oscillate in the high Megahertz spectrum if you let them, blowing all your tweeters and blotting out radio reception in a one mile radius and making colored stripes on your TV. Some of the power tubes like 807, 812A and GU50 are actually VHF transmitter tubes and especially prone to oscillation. They just happen to be available and well suited for audio too.

Common for all: We are playing with lethal voltages and remember: a capacitor may hold enough charge to halt your heart even after being powered off for days.

The designs are by and large my own, but of course I found inspiration elsewhere and there are only so many variations to a theme. Some of the switched-mode power supply circuits are based on manufacturer application notes and/or influenced by my esteemed fellow writers and contributors to audio fora around the world. I don’t copy – I get inspired.

17

BLUBOTTLE – small amp, big sound

1. BLUBOTTLE – small amp, big sound A Bluebottle (Portuguese Man of War, Latin: Physalia Utriculusis) is a small, but extremely poisonous jellyfish found in Australian waters.

The BLUBOTTLE amplifier – like the Bluebottle jellyfish - may not look much apart from the optional blue lighting of the tubes, which inspired the name, but rest assured: The sound quality of this small amplifier is second to none, especially with an effective speaker like the HORIZON Transmission Line or other equally high-efficiency speakers.

Depending on the quality and brand of the output tube (EL84/6BQ5 or better still E84L) the maximum power output is up to 5.7-6 W RMS over the whole frequency range.

The prototype was populated with NOS Siemens E84L Special Quality tubes, which allowed an output of 6 W at a frequency range of 30 Hz to 30 kHz ± 0.5 dB using a non-inductive output load, i.e. power bandwidth with less than 1% distortion. E84L is available on eBay at a price but beware of copies. A genuine E84L will last a lifetime and is a comparatively good investment but they do not sound better than any other EL84. They just don’t burn out and retain their properties for a long time.

The power bandwidth has a lot to do with the recommended output transformer. Alternative output transformers may not produce the same results since the output transformers are critical components as are the coupling capacitors.

Paper type caps like Jensen or other high quality, low-induction brands must be used for coupling capacitors.

Cheap PVC caps are a waste of time and will seriously impose on the sound quality and stability to the point, where phase-shift in a low-grade capacitor may lead to self-oscillation.

Non-inductive Polypropylene film capacitors often show performance close to oil caps and are a lot cheaper. At the time of writing the paper/oil caps used are typically US$ 50 each.

Unfortunately the quality spread between different film-cap brands is significant and you will have to read through the manufacturer’s specs carefully before choosing an alternative to the Jensens.

More often than not self inductance is not specified.

The PCB layout for the Bluebottle will accommodate the bulky oil caps.

The BLUBOTTLE amplifier will satisfy even the most distinguishing connoisseur. Many prefer the clean, dry sound of a single-ended class-A amplifier to the more boomy and powerful sound of a push-pull circuit, and the 5-6 W output power per channel is more than adequate when using decent speakers. The amp is especially recommended for use with full frequency range speakers like Fostex FE series, Jordan-Watts or Lowther PM4 or similar. Excellent results have been achieved with all of the above.

General circuit description (left channel referenced) The power output stage is built around the EL84 tube V3 operating in pure class A. Due to the fairly low plate supply voltage (~320 VDC) I decided to use fixed grid bias in order to squeeze the last 11.5 W out of the power stage. Cathode bias will subtract the bias voltage from the ultimate peak-to-peak output swing and that we can do without.

Adjustable negative grid bias also allows for spread in tube data as opposed to cathode bias.

V3 is driven by V2B, ½ x ECC83/12AX7, using a fairly low value plate load resistor, 47kΩ. The normal value in similar designs would be 100 kΩ or even higher in order to achieve higher gain.

However, EL84 has a relatively high μ (amplification factor) resulting in a high grid capacitance (native grid capacitance times μ), the so-called Miller effect. The Miller effect reduces high frequency response.

The Miller Effect can be overcome by low impedance feed to g1 on V3, here achieved by using a low value for R 5, the plate load resistor of the driver stage.

It may be argued, that an ECC82/12AU7 or ECC81/12AT7 would be better suited as a driver tube.

Quite true but here we need the higher gain of an ECC83 and the feed impedance is low enough.

27

The Bottle Builder: A Compendium of Tube Amp Designs vol. 1 If opting for ECC82/ECC81 the negative feedback resistor R19 should be increased to 4.7kΩ or higher (for ECC82) in order to compensate for the lower gain. The tubes are physically interchangeable but introduction of other tubes, even within the same family, would require some further tweaking and is not recommended for beginners. Other tubes than ECC83 will work to a certain extent without component changes but not optimally.

Even if BLUBOTTLE is a stereo amplifier no balance control has been inserted because the total gain is just adequate as it is. Volume control R 23-1 and R 23-2 is a ganged potentiometer with 4 mm and 6mm concentric shafts enabling independent volume adjustment on both channels. However, if you really need a balance control you have serious problems elsewhere.

Since the PCB layout allows for any type of potentiometer to be used, the constant-gain volume/balance control of the Octopus amplifier elsewhere in this book may be adapted. Increasing the value of R19 to 3.9 kΩ or 4.2 kΩ will compensate for the gain loss.

SW1 is the input selector – no mystery there. Any decent wafer switch will in principle do.

Please refer to Figure 1-1 on page 39.

The Tone Control - is the well known and loved James passive type. With reasonable good audio taper potentiometers (AKA logarithmic or curve II – a rose by any other name) the one-o’clock position of the knobs will render the overall frequency response close to flat.

The regulation is app. ±12 dB for both bass and treble around a center frequency of nominally 1 kHz.

Admittedly: Tone controls always have a negative influence with respect to phase shift. Purists may omit the tone controls entirely and connect C4 directly to the top of R 23-1 and will find, that there is now plenty of gain.

If you really want to go overboard, then omit the tone controls entirely and implement the VOLUTILE Fletcher-Munson compensated attenuator described in Chapter 23 on page 315.

The Phono Stage BLUBOTTLE sports a rather unusual phono pre-amplifier: A cascode coupled dual triode with RIAA compensation fed to the input grid.

Two possible compensation curves are catered for: RIAA for vinyl LP’s and general old time 78 RPM. If other curves are desired C5 and C6 would need changing.

A cascode amplifier is inherently very quiet – in many ways better than pentodes and triodes in the usual runof-the-mill grounded cathode circuits.

Connoisseurs may frown and object, that the load on the phono cartridge is not constant at all frequencies due to the shifting reactance of the feedback circuit – an argument often brought forward with cathode feedback circuits too.

The Critics do have a point but impedances are very high and hence capacitors very small - the reactance of a 330 pF capacitor will not in any measurable or audible way impede upon the mechanical compliance of the 47 kΩ phono cartridge. The actual impedance of the cartridge is much lower than that anyway - 47 kΩ is just the recommended load.

The subjective impression of the phono stage: It sounds really good, no audible noise at all, even at high volume and a close adherence to the standard RIAA equalization curve provided 1% capacitor tolerances as specified in the bill of materials are met. If the noise level rises when connecting a cartridge you have thermal noise from the cartridge coils – not uncommon.

The solution is to insert a paper or MKH capacitor, 0.5 to 1 μF, in series with the cartridge to block the small DC current flow through the copper windings causing the noise. This may apply to MC step-up transformers too. Some transformers are extremely sensitive to DC, even with the small grid currents and some produce thermal noise as do some cartridges.

28

The Bottle Builder: A Compendium of Tube Amp Designs vol. 1 Reference

Part

Description

Mfr.

Mfr. Numbers

Dimension (mm)

Remarks

Layout Ref.

C16

100u 25V

100uF 25V electrolytic

Panasonic

RS 747-2067

6.3 x 11.2

Radial

CYL/D.300/LS.100/.034

C17

100N

100nF 630V paper/oil capacitor

Jensen

149720

32 x 46

Axial

C20

C18

330P

330pF 1% film cap

RS

RS 116-234

7.5 x 7.5

Radial

DISC/.200X.200/LS.250X.255/.034

C19

100P

100pF 1% film cap

RS

RS 116-206

7.5 x 7.5

Radial

DISC/.200X.200/LS.250X.225/.034

100N

100nF 630V paper/oil capacitor

Jensen

149720

32 x 46

Axial

C20

C20 C21

100P

100pF 1% film cap

RS

RS 116-206

7.5 x 7.5

Radial

DISC/.200X.200/LS.250X.225/.034

C22

33P

33pF 2.5% film cap

RS

RS 113-235

4x8

Radial

AX/.500X.200/.040

C23

1N5

1.5nF 1% film cap

RS

RS 116-278

7.5 x 7.5

Radial

DISC/.200X.200/LS.250X.225/.034

100N

100nF 630V paper/oil capacitor

Jensen

149720

32 x 46

Axial

C20

C24 C25

2N2

2.2 nF 1% film cap

RS

RS 116-284

7.5 x 7.5

Radial

DISC/.200X.200/LS.250X.225/.034

C26

22N

22nF 1% film cap

Vishay

RS 166-6443

5.5 x 7.5

Radial

RAD/.200X.100/LS.100/.031

C27

470u 25V

470uF 25V electrolytic

Panasonic

RS 365-4155

10 x 12.5

Radial

CYL/D.400/LS.200/.034

C28

10P*

Polystyrene film cap 2.5%

RS

RS 113-207

4Ă˜ x 8

Axial

DISC/.200X.200/LS.250X.225/.034

C29

10N

10nF 1% film cap

Vishay

Rrs 166-6421

5.5 x 7.5

Radial

RAD/.200X.100/LS.100/.031

C30

100u 25V

100uF 25 V electrolytic

Panasonic

RS 747-2067

6.3 x 11.2

Radial

CYL/D.300/LS.100/.034

C31

100N

100 nF film cap

Panasonic

RS 727-0051

5.1 x 13

Radial

RAD/.475X.175/LS.400/.034

C32

100u 25V

100uF 25 V electrolytic

Panasonic

RS 747-2067

6.3 x 11.2

Radial

CYL/D.300/LS.100/.034

C33

100u 63V

100uF 63 V electrolytic

Panasonic

RS 315-0962

10 x 12.5

Radial

CYL/D.400/LS.200/.034

C34

100N

100nF film cap

Panasonic

RS 727-0051

5.1 x 13

Radial

RAD/.475X.175/LS.400/.034

C35

100N

100nF film cap

Panasonic

RS 727-0051

5.1 x 13

Radial

RAD/.475X.175/LS.400/.034

C36

100N

100nF film cap

Panasonic

RS 727-0051

5.1 x 13

Radial

RAD/.475X.175/LS.400/.034

C37

100N

100nF film cap

Panasonic

RS 727-0051

5.1 x 13

Radial

RAD/.475X.175/LS.400/.034

C38

100N

100nF film cap

Panasonic

RS 727-0051

5.1 x 13

Radial

RAD/.475X.175/LS.400/.034

C39

100N

100nF film cap

Panasonic

RS 727-0051

5.1 x 13

Radial

RAD/.475X.175/LS.400/.034

C40

22u 350V

22uF 350V electrolytic

Nichicon

RS 739-4541

12.5 x 20

Radial

CYL/D.500/LS.200/.040

C41

22u 350V

22uF 350V electrolytic

Nichicon

RS 739-4541

12.5 x 20

Radial

CYL/D.500/LS.200/.040

C42

22u 350V

22uF 350V electrolytic

Nichicon

RS 739-4541

12.5 x 20

Radial

CYL/D.500/LS.200/.040

C43

470u 400V

470uF 400V large can electrolytic

Panasonic

RS 127-694

35 x 45

Mount on reverse side

CYL/D.1.378/LS.390/.040

C44

100u 400V

Electrolytic capacitor

Panasonic

RS 575-361

22 x 30

Radial

CCYL22_10

C45

100N

100nF film cap

Panasonic

RS 727-0051

5.1 x 13

Radial

RAD/.475X.175/LS.400/.034

C46

2200 u 35 V

2200uF 35 V electrolytic

RS

707-6675

16 x 36

Axial

AX/1.775X.675/.050

C47

470u 63V

470uF 63V electrolytic

Panasonic

RS 756-8360

12.5 x 25

Radial

CYL/D.500/LS.200/.040

C48

470u 63V

470uF 63V electrolytic

Panasonic

RS 756-8360

12.5 x 25

Radial

CYL/D.500/LS.200/.040

C49

100N

100 nF film cap

Panasonic

RS 727-0051

5.1 x 13

Radial

RAD/.475X.175/LS.400/.034

C50

100N

100 nF film cap

Panasonic

RS 727-0051

5.1 x 13

Radial

RAD/.475X.175/LS.400/.034

D1

33V 5W

1N5364BRLG

ON Semi

RS 625-6467

3.68 x 8.89

Axial

DAX/.550X.120/.046

D2

1N4148

Si-diode

Vishay

RS 700-3674

1.7 x 3.9

Axial

DAX/.350X.080/.031

D3

1N4148

Si-diode

Vishay

RS 700-3674

1.7 x 3.9

Axial

DAX/.350X.080/.031

D4

1N4148

Si-diode

Vishay

RS 700-3674

1.7 x 3.9

Axial

DAX/.350X.080/.031

D5

1N4148

Si-diode

Vishay

RS 700-3674

1.7 x 3.9

Axial

DAX/.350X.080/.031

34

BLUBOTTLE – small amp, big sound Reference

Part

Description

Mfr.

Mfr. Numbers

Dimension (mm)

Remarks

Layout Ref.

D7

LED/blu

3mm high intensity blue LED

Kingbright

RS 247-1561

Ø3 x 4.6

Radial

CYL/D.150/LS.100/.031

D8

LED/blu

3mm high intensity blue LED

Kingbright

RS 247-1561

Ø3 x 4.6

Radial

CYL/D.150/LS.100/.031

D9

LED/blu

3mm high intensity blue LED

Kingbright

RS 247-1561

Ø3 x 4.6

Radial

CYL/D.150/LS.100/.031

D10

LED/blu

3mm high intensity blue LED

Kingbright

RS 247-1561

Ø3 x 4.6

Radial

CYL/D.150/LS.100/.031

D11

LED/blu

3mm high intensity blue LED

Kingbright

RS 247-1561

Ø3 x 4.6

Radial

CYL/D.150/LS.100/.031

D12

LED/blu

3mm high intensity blue LED

Kingbright

RS 247-1561

Ø3 x 4.6

Radial

CYL/D.150/LS.100/.031

D13

LED/blu

3 mm high intensity blue LED

Kingbright

RS 247-1561

Ø3 x 4.6

Radial

CYL/D.150/LS.100/.031

D14

LED/blu

3mm high intensity blue LED

Kingbright

RS 247-1561

Ø3 x 4.6

Radial

CYL/D.150/LS.100/.031

D15

KBU4G VISHAY

3A bridge rectifier

Vishay

RS 629-6667

7.1 x 23.7

Radial

BRDG4A

D16

18V 5W

1N5355BG

ON semi

RS 464-031

3.68 x 8.89

Axial

DAX/.550X.120/.046

D17

1N4007

Si rectifier diode 1N4007

Vishay

RS 708-7984

2.7 x 5.2

Axial

DAX/1N_4001-4007

D28

1N4007

Si rectifier diode 1N4007

Vishay

RS 708-7984

2.7 x 5.2

Axial

DAX/1N_4001-4007

D29

1N4007

Si rectifier diode 1N4007

Vishay

RS 708-7984

2.7 x 5.2

Axial

DAX/1N_4001-4007

D30

1N4007

Si rectifier diode 1N4007

Vishay

RS 708-7984

2.7 x 5.2

Axial

DAX/1N_4001-4007

D31

1N4007

Si rectifier diode 1N4007

Vishay

RS 708-7984

2.7 x 5.2

Axial

DAX/1N_4001-4007

J1

Phono input L

Phono jack PCB mount

Monacor

34.1740

11 x 18

PHONO1

J2

Phono input R

Phono jack PCB mount

Monacor

34.1740

11 x 18

PHONO1

J3

Tuner input L

Phono jack PCB mount

Monacor

34.1740

11 x 18

PHONO1

J4

Tuner input R

Phono jack PCB mount

Monacor

34.1740

11 x 18

PHONO1

J5

CD input L

Phono jack PCB mount

Monacor

34.1740

11 x 18

PHONO1

J6

CD input R

Phono jack PCB mount

Monacor

34.1740

11 x 18

PHONO1

J7

iPod input L

Phono jack PCB mount

Monacor

34.1740

11 x 18

PHONO1

J8

iPod input R

Phono jack PCB mount

Monacor

34.1740

11 x 18

PHONO1

J9

PLATE L

conn.lug

3mm rivet

MHOLE

J10

NFB L

conn.lug

3mm rivet

MHOLE

J11

NFBGND L

conn.lug

3mm rivet

MHOLE

J12

PLATE R

conn.lug

3mm rivet

MHOLE

J13

NFB R

conn.lug

3mm rivet

MHOLE

J14

NFBGND R

conn.lug

3mm rivet

MHOLE

J15

Va

conn.lug

3mm rivet

MHOLE

J16

CHOKE OUT

conn.lug

3mm rivet

MHOLE

J17

CHOKE IN

conn.lug

3mm rivet

MHOLE

J18

POWER HEADER

Molex

PWRCONN10

MH1

MOUNT

mounting hole

MHOLE

MH2

MOUNT

mounting hole

MHOLE

MH3

MOUNT

mounting hole

MHOLE

MH4

MOUNT

mounting hole

MHOLE

35

5

R65

1K TRIM

R46 47K*

R67 56K

100N

C36

R61 820K

100u 64V

C33

10P*

C28

R68 2K7

Q1 BC547 C38

D2

1M

1N4148

100N 1N4148

D4

C34 100N

R62 47K

4

4

f1

V7

3 R88

1

C30

9

R58 10K

fb

5

7

6 EM84

Vb

R48 10M

R44 220K

100u 25V

R57 470K

R47 2K2

8

7 R43 1K

C15 47N

IPOD

C31 47N

IPOD

CD

TUNER

COMPUTER

C17 100N

1

2

1 V4A ECC83/12AX7

5 9 4 3

470K

R21 10M

f1 f2 V4B 6 ECC83/12AX7

R36 680K

C22 33P

R32 680K

C19 100P

Vd

100u 25V

C14

J9

R35 10M

C21 100P

R31 10M

C18 330

R29

R20 2K2

8

R16 220K

CD

TUNER

COMPUTER

R51 1M

1

J10

1

J8

1

J7

1

J6

R24 1M

1

J5

1

J3

1

J2

1

J1

FBleft

1K TRIM

R66

R52 470K

INP SELECTOR R

SW1A2

R25 470K

INP SELECTOR L

SW1A1

1K

2

f2

100K

R30

Vc

3

R69 56K

100N

f2

1Mlog

R10-2

R34 100K

C20 100N

C32 100u 25V

f1

3 4 9 5

R63 820K

R53 2K2

2

R10-1

R6 100K

C4 100N

C16 100u 25V

f1

3 4 9 5

V5A ECC83/12AX7 1

R26 2K2

C37

R37

1K

R11

100K

R2

Vc

V2A ECC83/12AX7 1

3

R70 2K7

Q2 BC547

100N 1N4148

C39

D3

1M

1N4148

D1 33V 5W

D5

82K

R39

82K

R9

fb

3 R89 4

1

V8

9

10N

C29

R38-2

1N5

C23

10N

C13

R38-1

1N5

R59 470K

R56 100K 2W

22N R49 22K

C26

C35 100N

R64 47K

1Mlog

C25 2N2

22N R22 22K

C10

C9 2N2

C7 1Mlog

f2

5

7

6 EM84

Vb

R60 10K

1Mlog + TREBLE -

A

FBright

PHONO R

78RPM

RIAA

SW1-2

R18 47K*

CORRECTION

10P*

C12

R15 1K

7

5 9 4 3

2

1 V1A ECC83/12AX7

C2 100N

1

R8 680K

C6 33P

R4 680K

R1 470K

f1 f2 V1B 6 ECC83/12AX7

R7 10M

C5 100P

R3 10M

C3 100P

J4

CORRECTION

78RPM

RIAA

SW1-1

C1 330

Vd

4

+ BASS -

B

C

PHONO L

2

2

32 32 32 2 32 32

+ BASS -

32

+ TREBLE -

2

D

5

R23-2 470KLOG

2

7

Vb

470u 25V

7

8

C24

100N

R54 150R

R45 1K5

C8

100N

R27 150R

R17 1K5

V5B 6 ECC83/12AX7

C27

1K

R40

8

R33 47K 1W

470u 25V

C11

1K

R5 47K 1W

Vb

V2B 6 ECC83/12AX7 R12

VOLUME

470KLOG R23-1

2

1K

R42

Date:

Size A3

Title

Vg1R

TP2

3

2

9

3K3

R19

100R

R13

4

5 f2

R55 10R 1W 1%

fa

9

3K3

R50

100R

R41

5K:8R LL1663/50mA T2

Va

R28 10R 1W 1%

5 fa

4 f1

V6 7 EL84/6BQ5

TP1

3

2

V3 7 EL84/6BQ5

FBright

FBleft

1

1

SP2

SP1

SP4

SP3

Vb

1

1

Vb

R SPKR-

R SPKR+

L SPKR-

L SPKR+

Friday, November 14, 2014

2013-01-A

Document Number

1

Sheet

1

of

2

BLUBOTTLE SE Stereo amp 2 x 5.6W CLASS A

© 2014 Bergqvist Copenhagen

480mV

Vg1L

480mV

1K

R14

Va 5K:8R LL1663/50mA T1

1

Rev B

A

B

C

D

BLUBOTTLE – small amp, big sound

Figure 1-1 Main circuit

39

A modular preamplifier

8. A modular preamplifier This preamplifier was designed as the centerpiece for a large audio installation with 2 x Sterling amplifiers (see Chapter 9 on page 147) + 1 Substory subwoofer amplifier (see Chapter 18 on page 287).

Two turntables are connected each to its separate phono preamplifier and two tape recorders, one reel-to-reel and one DAT.

The main amp (See Figure 8-1 on page 141) may be used as a stand-alone line preamp/tone control with just about any stereo power amplifier if you do not need phono preamps and crossovers for channel amplification.

Since the design is modular you may add or remove any module you feel like or use them as standalone functional units in other contexts – or simply as inspiration to your own designs.

An Overview Figure 8-6 on page 146 shows how the modules interconnect. All modules have a 6-pole multi-connector, which may be interconnected every which way without actually harming the modules. All connectors are configured like this: Pin 1 V+ plate voltage Pin 2 f1 heater

Pin 3 f2 heater

Pin 4 Left channel (when applicable)

Pin 5 Right channel (when applicable) Pin 6 common/GND

The above effectively means, that a phono module may be hooked up directly to the power supply.

It will heat up and work as such, but there are no output pins connected to anything.

Two different versions of phono preamps are offered:

Figure 8-3 on page 143: A pentode input RIAA only preamp with negative feedback de-emphasis.

Figure 8-4 on page 144: A multi-standard phono preamp for older records with a rumble filter to counteract subsonics from warped LP’s, old 78 RPM records and less-than-ideal turntables.

You may use one of each phono preamp, the same in both positions or none at all according to your personal preferences and needs.

The regulated power supply is common for all modules. Power is fed to the line amp main module and distributed from there to all the peripheral modules.

The crossover module is optional – if you are not going for channel amplification you can omit it and connect directly to a power amplifier from the main module. However, the output impedance is fairly high and requires some 250 kΩ input impedance or higher from the following stage and no too long signal cables whereas the output impedance from the crossover module is very low and will allow 3-5 metres of signal cable without high frequency loss.

Channel Amplification versus bi-amping Channel amplification is exactly what the name implies: The audio signal is divided up into two or more spectrums, each being fed to its designated power amplifier thereby eliminating the requirement for crossover filters in the speaker systems and allowing speakers with different efficiency to work together.

Speaker crossover filters are – if they are any good, that is – bulky and expensive and present a complex load to the power amplifier.

125

The Bottle Builder: A Compendium of Tube Amp Designs vol. 1 The frequency-determining circuits are all three-pole Butterworth filters giving a theoretical flank of 18 dB/ octave. The phase errors are pretty constant over the whole frequency range and you will fell no ‘alienation,’ i.e. the unpleasant sensation you get when part of the programme material is out of phase relative to the rest.

When the phase twist is uniform or close to it over the whole range it does not matter.

Note, however: If you are running the satellite left and right channels at full range together with the subwoofer channels you will have to reverse phase the woofers, because they will be 180 out of phase with the satellites at full range.

18 dB/octave ensures, that the mid/high frequency units are definitely not subjected to low frequencies, which may destroy them, depending of the choice of speakers, but third-order filters reverses the phase twice relative to the input.

In my experience even the satellite left and right speakers should be full-range units. I cannot tell you why but subjectively they sound better even if they are not fully utilized in the low spectrum.

The filters exhibit the following attenuation at various frequencies as follows: Table 8-1 Filter attenuation at various frequencies Frequency

High Frequency channel

Low Frequency channel

200Hz

-32dB

0dB

300Hz

-23dB

0dB

400Hz

-16dB

-0.2dB

500Hz

-11dB

-0.3dB

600Hz

-8dB

-1dB

700Hz

-5dB

-2dB

800Hz

-3dB

-3dB

900Hz

-1.5dB

-5dB

1kHz

-0.3dB

-7dB

1.6kHz

-0.2dB

-18dB

2kHz

0dB

-22dB

3kHz

0dB

-33dB

4kHz

0dB

-40dB

Below approximately. 350 Hz there is no attenuation on the bass side and beyond 1.8 kHz there is no attenuation of the treble.

The crossover filters when active attenuate the audio signal by a factor of 1:0.8.

The output phono jacks protrude through the cabinet’s rear panel like the ones on the phono stages.

The phono preamps The two phono preamps, Figure 8-3 on page 143 and Figure 8-4 on page 144 share the same PCB footprint and are thus physically interchangeable. The input connectors protrude through the back plate of the cabinet and the de-emphasis selector switch on Figure 8-4 on page 144 protrudes through the front panel.

The multi standard Figure 8-4 on page 144 is the more interesting of the two inasmuch as it offers a wide variety of playback curves suitable for nearly all phonograph record, new and old.

‘78’ is for post-1927 pre-1959 78 RPM records.

‘AES’ is for the pre-stereo (1958) LP and EP mono records.

‘COL’ is for pre-RIAA stereo and mono LP and EP (typically from the early 1960’es).

‘RIAA’ is for the post-1958 stereo LP and EP records.

‘FFSS’ or Full Frequency Stereophonic Sound is for the British Decca ‘Phase 4’ records, offering spectacular stereo sound from 1953-54 before the rest of the world went stereo and RIAA in 1958.

128

The Bottle Builder: A Compendium of Tube Amp Designs vol. 1 Table 8-4 SENTRY - Modular Preamp, Riaa-2 components Reference

Part

Description

C1

220u 350V

350 V electrolytic cap

C2

220N

400V oil cap

C3

10N

1% 50V polystyrene

C4

220N

400V oil cap

C5

100P

1% 50V polystyrene

C6

100u 16V

C7

2680P 1%

1% 50V polystyrene

C8

100P 1%

1% 50V polystyrene

C9

2.0N 1%

1% 50V polystyrene

C10

240P 1%

1% 50V polystyrene

C11

1.68n 1%

1% 50V polystyrene

C12

310P 1%

1% 50V polystyrene

C13

200P 1%

1% 50V polystyrene

C14

390P 1%

1% 50V polystyrene

C15

1N 1%

1% 50V polystyrene

C16

510P 1%

1% 50V polystyrene

C17

220N

400V oil cap

C18

10N

1% 50V polystyrene

C19

220N

400V oil cap

C20

100P

1% 50V polystyrene

C21

100u 16V

16V electrolytic cap

C22

2680P 1%

1% 50V polystyrene

C23

100P 1%

1% 50V polystyrene

C24

2.0N 1%

1% 50V polystyrene

C25

240P 1%

1% 50V polystyrene

C26

1.68n 1%

1% 50V polystyrene

C27

310P 1%

1% 50V polystyrene

C28

200P 1%

1% 50V polystyrene

C29

390P 1%

1% 50V polystyrene

C30

1N 1%

1% 50V polystyrene

C31

510P 1%

1% 50V polystyrene

J1

INP LEFT

RCA phono jack

J2

OUTPUT/POWER

6-way header

J3

INP RIGHT

RCA phono jack

R1

5K1 2W

2W 5% metal film resistor

R2

4M7

0.4W 1% metal fil resistor

R3

240K

0.4W 1% metal fil resistor

R4

100K

0.4W 1% metal fil resistor

R5

47K 1%

0.4W 1% metal fil resistor

R6

1M

0.4W 1% metal fil resistor

R7

2K2

0.4W 1% metal fil resistor

R8

5K1

0.4W 1% metal fil resistor

R9

15M

0.4W 1% metal fil resistor

R10

15M

0.4W 1% metal fil resistor

R11

200K 1%

0.4W 1% metal fil resistor

R12

15M

0.4W 1% metal fil resistor

R13

200K 1%

0.4W 1% metal fil resistor

R14

4M7

0.4W 1% metal fil resistor

R15

200K 1%

0.4W 1% metal fil resistor

138

A modular preamplifier Reference

Part

Description

R16

1M5

0.4W 1% metal fil resistor

R17

200K 1%

0.4W 1% metal fil resistor

R18

15M

0.4W 1% metal fil resistor

R19

200K 1%

0.4W 1% metal fil resistor

R20

4M7

0.4W 1% metal fil resistor

R21

240K

0.4W 1% metal fil resistor

R22

100K

0.4W 1% metal fil resistor

R23

47K 1%

0.4W 1% metal fil resistor

R24

1M

0.4W 1% metal fil resistor

R25

2K2

0.4W 1% metal fil resistor

R26

5K1

0.4W 1% metal fil resistor

R27

15M

0.4W 1% metal fil resistor

R28

15M

0.4W 1% metal fil resistor

R29

200K 1%

0.4W 1% metal fil resistor

R30

15M

0.4W 1% metal fil resistor

R31

200K 1%

0.4W 1% metal fil resistor

R32

4M7

0.4W 1% metal fil resistor

R33

200K 1%

0.4W 1% metal fil resistor

R34

1M5

0.4W 1% metal fil resistor

R35

200K 1%

0.4W 1% metal fil resistor

R36

15M

0.4W 1% metal fil resistor

R37

200K 1%

0.4W 1% metal fil resistor

SW1

RUMBLE FILTER

DPDT toggle switch

SW2

DE-EMPHASIS

Rotary switch 2P 5T

V1

ECC83

Dual triode noval

V2

ECC83

Dual triode noval

139

Figure 8-4 RIAA-2

A

B

C

5

4

1

INP RIGHT J3

4

8

f2

SW2A

R8 5K1

f1

3 4 9 5

1

1A 2A 3A 4A 5A

220N

C2

R3 240K

V2A

f2

220N

C17

1B 2B 3B 4B 5B COMPENSATION

SW2B

R26 5K1

f1

3 4 9 5

8B

2

1

R21 240K

DE-EMPHASIS

2

ECC83

R23 47K 1%

C20 100P

V1A ECC83

R5 47K 1%

C5 100P

1 = 78 2 = AES 3 = RIAA 4 = COL 5 = FFSS

1

INP LEFT J1

2

144 2

D

5

15M

R27

15M

R9

IN

15M

8

200K 1%

R7 2K2

R4 100K

2.0N 1% C10 240P 1% 4M7 R15 200K 1%

C8 100P 1% R13 200K 1%

R11

7

ECC83 6

V1B

R2

SW1-2

1N 1%

IN

15M

V2B

8

200K 1%

R25 2K2

C23 100P 1% R31 200K 1%

R29

7

R22 100K

R20

510P 1%

ECC83 6

C16

C30

1N 1%

C31

3

510P 1%

C28 200P 1% C29 390P 1% R36 15M R37 200K 1%

C26 1.68n 1% C27 310P 1% R34 1M5 R35 200K 1%

C24 2.0N 1% C25 240P 1% R32 4M7 R33 200K 1%

C22 2680P 1% R30 15M

R28

R24 1M

10N

C18

OUT RUMBLE FILTER

C15

C13 200P 1% C14 390P 1% R18 15M R19 200K 1%

C11 1.68n 1% C12 310P 1% R16 1M5 R17 200K 1%

C9 R14

C7 2680P 1% R12 15M

R10

R6 1M

10N

C3

OUT RUMBLE FILTER

SW1-1

3

C21 100u 16V

220N

C19

4M7

C6 100u 16V

220N

C4

4M7

f1 f2

5K1 2W C1 220u 325V

R1

J2

1 2 3 4 5 6

+V f1 f2 OUT LEFT OUT RIGHT GND

2

OUTPUT/POWER

1 2 3 4 5 6

2

Date:

Size A3

Title

Saturday, October 25, 2014

Document Number 2013-08-D

1

Sheet

1

SENTRY - MODULAR PREAMP, RIAA-2

© 2014 Bergqvist Copenhagen

1

of

1

Rev A

A

B

C

D

The Bottle Builder: A Compendium of Tube Amp Designs vol. 1

5

MS1 MS2

f1 f2 100u 400V

C1

R8

R16 1K

100P

C7

Q1

4

1K

R15

Q2 MJE13003

6V8 .5W R4 82K

D2

18R 2W

100K CERMET

470N 400V

C2

10K 0.6W

R3

TL431 U2

R11 100R

R12 820K

R5 1K 0.6W

STD2NK100Z

R13 22K

R6 270K

R7 56K

f2

f1

R2 270K

C5 100N

ADJ

3

5000u 100V

C6

4

3

ADJ. R13 FOR f1/f2 = +12.6VDC

R14

1K CERMET

VIN

LM350

VOUT

240R

R9

2

U1

C4 220u 250V

C3 220u 250V 1

T1

23

5

7

115V

6 8

115V

MS2

STANDBY LED

D5

MAINS TRANSFORMER

17V 3A

2 4

170V 150mA

D3 1N4007

D4 10A 100V

D1 1N4007

C8

D6

2

1 2

5

3

T2

9V 500mA

4

1

RELAY 8V

LS1

1N4001

100u 10V

R10 1K

MS1

6

4

8

5

500mA F1

Title

J2

MAINS 230V

1 2 3

© 2014 Bergqvist Copenhagen

STANDBY TRANSFORMER

SW DPST

SW1

C

Date:

Size A3

Saturday, October 25, 2014

Document Number 2013-08-E

1

Sheet

1

of

1

Rev A

SENTRY - MODULAR PREAMP, POWER SUPPLY

A

POWER

1 2 3 4 5 6

R1

D

A

+V f1 f2 X X GND

ADJ. R8 FOR 325VDC REG

1

B

1 2 3 4 5 6

J1

2

B

C

D

1

3 1

3

+

4

-

5

A modular preamplifier

Figure 8-5 Power supply

145

The Leak Tweak – case for beefing up a TL12+

24. The Leak Tweak – case for beefing up a TL12+ One of the best sounding power amplifiers ever was/is the LEAK TL12+ and I happen to own two wellpreserved specimens in mint condition – now. That was not always the case.

One of the main reasons for the good sound was the output transformer, which was/is in a class of its own.

They are both dated 1959 and time took its toll on the capacitors and the tubes.

The preamps for them disappeared long time ago when mono went out of fashion and they have been used with a home-brew stereo preamp for years.

The time came when one of the amps started to distort heavily. Changing the tubes did not help so on the bench it went.

The culprit turned out to be a leaky C10 (see Figure 24-1 on page 327 – the original schematics) and it had taken V4 and cathode resistor R19 with it plus ultimately C11, which as a last gesture had spread its appetizing contents over most of the tag board.

The first thing to do was of course to change all the signal-path capacitors C4, C8, C9 and C10, which helped a lot.

C4 should be upped to 220 nF 300 V paper/oil cap, C9 to a 220 nF 100 V paper/oil cap, C11 and C12 to 470 nF 400 V paper/oil caps. The larger values have to do with the power tube cathode mods offering a much better low bass response.

With a NOS pair of EL84’s, new cathode resistors, R19 and R 20, and replacement of C11 and C12 it played nicely again only to reveal, that the other TL12+ needed attention too: The repair sounded much better than the other one.

A few measurements showed, that one of the GZ34 rectifier tubes was definitely singing its death song. The plate supply had ripple indicating, that one of the sections was close to defunct.

The time had come for a real restoration job. In a way I was lucky, that I did not lose an output transformer because it must have been subjected to a lot of DC for a long time. It got pretty hot but survived. Replacement OPT’s are really, really hard to come by.

Many years back I mounted phono jacks on the rear for signal input. Leaving the preamp octal socket unused as such, but I had tinkered together the little magic eye thing shown in Figure 24-2 on page 328.

Too much? Well, maybe so, but a lot prettier than a dull old pilot light. You may alternatively remove the octal socket and adapt a noval one and mount the EM84 tube directly.

The same circuit is used elsewhere in this book and needs little explanation. With the transistor preamp stage there is enough sensitivity to match the amplifier’s rated input of 125 mV for full power. Simply adjust R6 to you liking and enjoy your nostalgic disco show.

Replacing all the signal caps with Jensen paper/oil types certainly made a difference. You do not realize the gradual deterioration of the old caps. Small wonder – after all they were 55 years old, so what can one expect?

I had the choice between replacing both GZ34 rectifier tubes in order to keep and do something else – so I decided to do something else:

First a replacement of the smoothing capacitors C13 and C14. These two caps are actually one and the same unit in a nicely painted housing.

Unsolder the connections and remove the cap. We need to preserve the housing to retain the original looks of the amplifier, but the innards have to be removed.

This is not a difficult task: Throw the capacitor into a pot of boiling water and after a while the content melts and expands and is easily pulled out.

The electrolytic compound smells really bad, by the way.

Then you can remount the metal can and place the new C13 (470 μF 450 V) from underneath, fixing it with a bit of silicone padding.

321

The Bottle Builder: A Compendium of Tube Amp Designs vol. 1 Mount C14, which is much smaller, near the rectifier tube and glue it onto the chassis near the rectifier tube V5 and connect + to pin 8 on the GZ34 socket and the negative to the nearby ground lug for C12 (references are made to the original LEAK schematics).

C13A is mounted between the output transformers center tap and the nearest ground. It serves to enhance the high frequency and transient response and it works best when mounted directly. The cap must be a 400 V paper/oil type to make a difference.

Replace R 22 on the tag board with a 100 Ω 10 W wire-wound resistor. Since C13 now has more than 10 times the capacity of its predecessor the in-rush charging current is considerable, so the old R 22 may blow out. Better change it before it does.

So far, so good. Now for something completely different.

A virtual rectifier tube As you may have noticed the new smoothing caps are 450 V types when 400 apparently would be adequate.

There is good reason.

GZ34’s are not difficult to find. The Russian Svetlana ones are really good if you cannot lay your hands on some NOS Mullards (that’ll be the day), but why not deal with the aging problem once and for all?

The obvious answer is of course to replace the rectifier tube with high-voltage silicon diodes like 1N4007: 1000 V reverse voltage rating , 1 A continuous current and a very high avalanche (in-rush current, slightly different with various brands but more than enough) – and they never wear out.

Two major issues here:

One of the advantages of using rectifier tube is, that it delays the plate supply until the power tubes are heated and stable, simply because the rectifier tube itself takes a while to heat up.

The gradual warming of the heaters also means soft start, protecting components in the plate supply from excessive charging currents – which is why R 22 should to be replaced as a safety measure, for there is no way to make a soft start high voltage circuit in a simple way, that is small enough to fit the mechanical constraints to be defined in a while.

In-rush current we can deal with but we need a 30-second delayed plate supply to make sure the power tubes are sufficiently heated and stable.

Meet the virtual GZ34 rectifier tube in Figure 24-4 on page 330.

This design replaces a GZ34 rectifier tube (and practically all others too) using an octal plug + a printed circuit board with rectifier diodes, MOSFET switch and a 20 second delay circuit. No modification to existing amps are required – just plug it in and off you go.

A GZ34 has 4 connections:

Pins 2 and 7: the two rectifier plate sections Pin 2

Pin 8

5V heater

5V heater and cathode

The virtual GZ34 uses two 1N4007 rectifier diodes instead of the tube rectifier.

Each diode is preceded by a 100 Ω series resistor. This resistor is not only there for current- and voltage limiting but also for high frequency switching noise suppression. Rectifier tubes are slow and mellow whereas silicon diodes are fast – and they generate noise.

Each diode is shunted with C2 and C3, a 470 pF high voltage ceramic disc cap for further noise reduction.

It is important to use very high voltage caps (these are specified for 3,000+ V) for effective switching noise quenching and they must be non-inductive single disc types.

The 1000 V MOSFET transistor Q1 acts as an on/off switch. R4 serves as a current limiting device, reducing the max. current to 450mA – something, that looks like a softer start, at least..

The zener diode D3 ensures, that the max. gate/source voltage for the device is not exceeded.

322

The Leak Tweak – case for beefing up a TL12+

Bill of Materials The BOM for the Leak Tweak components are given in the following tables.

Table 24-1 Leak Tweak - components Reference

Part

Description

Mfr.

Mfr. Numbers

Dimension (mm)

Remarks

Layout Ref.

C1

100u

63v electrolytic

RS

RS 707-6559

Ø10 X 21

AX/.800X.325/.031

C2

100u

63v electrolytic

RS

RS 707-6559

Ø10 X 21

AX/.800X.325/.031

C3

100u

63v electrolytic

RS

RS 707-6559

Ø10 X 21

AX/.800X.325/.031

C4

100u

63v electrolytic

RS

RS 707-6559

Ø10 X 21

AX/.800X.325/.031

C5

1u 100V

D1

Vz=4V7

4,7V ± 2% 0.5W zener diode

MH1

E84L CATHODE

connector lug

MHOLE

MH2

GND

connector lug

MHOLE

MH3

MOUNT

connector lug

MHOLE

MH4

MOUNT

connector lug

MHOLE

Q1

STF19NF20

MOSFET 200V 15A n-channel

Vishay

RS 761-0095

TO220AA/RF3

Q2

BF422

250V NPN

Vishay

RS 508-440

TO5

R1

10K

0.4W metal film resistor

Vishay

RS 683-2709

Ø1.6 x 3.6

R4

R2

270R

0.4W metal film resistor

Vishay

RS 683-2793

Ø1.6 x 3.6

R4

R3

120R

5W WW resistor

Vishay

RS 683-0964

Ø5.5 x 16.5

NXP

RS 508-254

26 x 7 x 16.5

Radial

C8_8

Ø1.85 x 4.25

Axial

AX/.400X.100/.031

Axial

R8

Table 24-2 Leak Tweak - Virtual GZ34 components Reference

Part

Description

Mfr.

Mfr. Numbers

Dimension (mm)

Remarks

Layout Ref.

C1

100u 16V

16V electrolytic

Panasonic

RS 116-824

Ø8 x 5 pitch 2.5

Radial

CYL/D.325/LS.125/.034

C2

470P

ceramic disc cap 3,150VDC

Murata

RS 117-366

Ø7 x 2 pitch 7.5

Radial

C3

C3

470P

ceramic disc cap 3,150VDC

Murata

RS 117-366

Ø7 x 2 pitch 7.5

Radial

C3

C4

47u 16V

16V electrolytic

Panasonic

RS 116-818

Ø6.3 x 5 pitch 2.5

Radial

CYL/D.250/LS.100/.031

C5

100N

50V polyester film cap

Wima

RS 115-023

3 x 7.5 x 4.6 pitch 2.5

Radial

C1

C6

47u 16V

16V electrolytic

Panasonic

RS 116-818

Ø6.3 x 5 pitch 2.5

Radial

CYL/D.250/LS.100/.031

D1

1N4007

1000V 1A rectifier diode

Vishay

RS 708-7984

DO41

DAX/1N_4001-4007

D2

1N4007

1000V 1A rectifier diode

Vishay

RS 708-7984

DO41

DAX/1N_4001-4007

D3

6V8

zener diode 0.5W

Vishay

RS 811-5977

DO35

DAX/.300X.050/.028

D4

1N4148

100 200mA switching diode

Vishay

RS 544-3480

Ø1.5 x 4.25

Axial

DAX/.300X.050/.028

D5

1N4148

100 200mA switching diode

Vishay

RS 544-3480

Ø1.5 x 4.25

Axial

DAX/.300X.050/.028

D6

1N4148

100 200mA switching diode

Vishay

RS 544-3480

Ø1.5 x 4.25

Axial

DAX/.300X.050/.028

JP1

OCTAL PLUG

Q1

STP2NK100Z

MOSFET 200V 15A n-channel

Vishay

RS 761-0095

R1

100R

2W WW resistor

Vishay

RS 788-8071

see text TO220AA/RF3 Ø4 x 10.2

Axial

R6

325

A

B

C 470P

C2

D1

PIN-6 PIN8

PIN2 PIN-2

1N4148

C6

PIN-8

PIN6

PIN-4

PIN4

47u 16V

C4

D6

100R 2W

1N4007

4

47u 16V

+

D2

1N4148

D4

100R 2W

1N4007

R4 15R 2W

C3

D3 6V8

R2 10K

Q1 STD2NK100Z 470P

3

7

3 DSCHG

OUT

MOUNT

MH1

CV

D5

8

4 6 2

5

1N4148

NE555

VCC

C1 100u 16V

U1

RST THRSD TRIG

GND 1

D

+

5

+

R5 270K

Date:

Size A4

Title

100N

C5

2

Tuesday, November 04, 2014

2013-24-E

Document Number Sheet

1

Leak Tweak Virtual GZ34 PCB version

© 2014 Bergqvist Copenhagen

1

of

1

Rev A

A

B

C

D

The Leak Tweak – case for beefing up a TL12+

Figure 24-5 Virtual GZ34 PCB version

331

The Bottle Builder: A Compendium of Tube Amp Designs vol. 1

Figure 24-6 Virtual GZ34 PCB

332

M/S stereo recording techniques

30. M/S stereo recording techniques As briefly mentioned in Chapter 2 on page 47 an alternative to the traditional A-B or left-right setup for stereo sound reproduction exists. It is called M/S or Mid/Side recording.

The techniques is widely used in studios for particular purposes like recording of drums and for live film sound recording under adverse conditions, where only one microphone position like an overhead mike (affectionately known as a Giraffe) is possible.

M/S recording has several advantages inasmuch as more spatial information is embedded into the recording facilitating post-production mixdown and stereo-image editing from a single microphone position.

You cannot do that with an A-B recording: It is fixed the moment it is on tape and nothing you can do except adding effects to it. If the A-B recording fails you have had it. An M/S recording can be doctored and microphone setup is a lot less critical.

How to do M/S recordings For M/S recording you need two microphones: One cardioid or omnidirectional (we will get to that later) and one figure-of-eight.

The first microphone is placed in the center, facing the band.

Placement of the microphone is not critical – simply consider where you would place it for a mono recording.

That is the spot. If you place it too close to the sound source it will tend to pick up more of the instruments in the middle than those placed left and right.

If you place it too far away you will get too much room colouring and booming sound. It is a good idea to use a pair of headphones while setting up the M mike: When it sounds OK as a mono signal you have found your spot.

Now for the S microphone. If you look at (A-1) in Figure 30-1 on page 366 you will see two microphones.

The M or middle microphone is blue and the S or side microphone is depicted as a double element (which it usually is) with the positive phase facing left (red for port, if you are a sailor) and the negative phase facing right - green for starboard). The M mike picks up most of the direct sound and the S mike picks up the ambience, i.e. reflected sound from the recording room.

This is how your setup should be with left and right viewed when facing the band, i.e. your left and right and not the band’s.

The S microphone is placed directly behind the M microphone with it’s figure-of-eight zones perpendicular to the direction to the band. That way it will pick very little up from the center pressure wave but a lot from reflected sound.

The two microphone signals are fed to the left and right inputs on a recording device.

You are now ready to rock and roll – literally. This is initially all there is to it and it is really hard to make a useless M/S recording as opposed to A-B recordings. All you have to do is watch the VU-meters. The balance between the M and S microphone is not important at this stage, but overloading the recorder cannot be corrected later.

What is actually happening here?

As you may suspect there is a little more to this than meets the eye.

A little math will explain it all:

In stereo music reproduction we basically have two signals: L = left channel

R = right channel 363

The Bottle Builder: A Compendium of Tube Amp Designs vol. 1

+

2-15 METRES

SOUND SOURCE

BLUE

Band

RED

SIDE SIGNAL, FIGURE-OF-EIGHT MIKE

_

R1

MID SIGNAL CARDIOID OR OMNIDIRECTIONAL MIKE

1 2 R2

_

GREEN

+

GREEN

_

Fig. A-1

+

RED

LEFT

INPUTS

RIGHT

3

Fig. A-2

recording device MIXING CONSOLE RED

Ch-1 assign right Left output to recorder Ch-2 assign left

BLUE

Right output to recorder GREEN

Fig. A-3

Ch-3 phase reverse assign right © 2014 Bergqvist Copenhagen Title Size A4 Date:

MS Stereo Recording Document Number Saturday , Nov ember 15, 2014

Figure 30-1 M/S recording

366

Rev A

2013-30-A

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1

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1

The Shrimp – Personal Guitar Amplifier Illustrations:

35. The Shrimp – Personal Guitar Amplifier Illustrations: Ever felt the urge to play a little off-stage for a while away from the huge Marshall arrays, spotlights and the cheering crowd?

If affirmative The Shrimp may be just the solution for you: A tiny, yet tasty little thing with an exceptional flavour.

Large guitar amps have built-in reverb units and some have tremolo – or both. The Shrimp has it all and is ideal for home use with its 8-10 W output power.

The reverb side is a little unusual since I don’t use a reverberation spring tank but a digital device from Accutronics, the same company, that still manufactures the original Hammond spring reverb units.

OK, so I did succumb to the modern solid-sate. I admit it. However, the rest is tube at its best and the result is truly amazing for an amplifier this size.

The speaker unit is an equally important part of the whole audio chain, weakest link and all. For the prototype I initially used a Monacor SP–200X 8” full-range unit, which produced a very crisp sound, suitable for semiacoustic guitars. However, it seemed to lack the punch you get with the classic amps like Fender, Marshall etc.

Later it was replaced by a Fane AXA-10 10” unit from the manufacturer’s Classic Guitar product line and it was indeed a vast improvement.

The SP-200X is a HiFi loudspeaker and as such not particularly suited for electric instruments. Guitar amps are not HiFi, nor were they ever intended to be. Not unlike potted shrimps: Nice, soft, mellow and a little boring.

Fane’s Classic Guitar series is in my perception the closest you get to the Jensen and JBL speakers of the 1950’s and 1960’s giving you that indefinable punch and general rock sound we all love.

Amplifier Schematics See Figure 35-1 on page 395

The basic circuit is ‘borrowed’ from a Marshall 1930 from early 1960’s. I prefer to call it ‘inspiration’ since a simple calculation would have ended up with the same component values, pretty much run-of-the-mill for the power amplifier. What is clever is the preamp/tremolo stage, half a longtailed pair, half a phase shift oscillator.

Obviously designed by a miser saving the company money for parts.

The clever design reduces the total number of tubes to three: One ECC83, V1, preamp/tremolo tube and two ECL86 triode-pentodes, V2 and V3, for the PP power amp.

The tone stack is extremely simple, but you will get to love it. It works really well providing a good balance between highs and lows, all with one knob, and with a low insertion loss.

The preamp stage consists of V1A and is in principle traditional: Plate resistor R1, cathode bias resistor R19/R 28 and a capacitive decoupling capacitor C10.

The part where it gets interesting is the low-frequency phase-shift oscillator around V1B. We need this oscillator to produce the tremolo effect, which is basically a low-frequency amplitude modulation of the audio signal from V1A mimicking vibrato. Subjectively I always thought it sounded terrible, but I has its uses if not overdone.

The frequency determining components are C4, C5, C3, C8, R11, R15 and R 20. Adjusting R 23 will also shift the frequency a bit, but not much.

The frequency can by varied with R 20 from approximately 2 Hz – 7 Hz which is about right. If you are dissatisfied with the range, try changing the value of C8 to 47 nF.

With R11 unconnected at the lower end, that oscillator will cease to work. If pin 2 on J2 is ported to ground the circuit will oscillate.

389

A

B

GUITAR INPUT

C J1

4 1 5 2 3 6

2K2

4N7

500K LOG R17 R26 39K

TREBLE-/BASS+

TREBLE+/BASS-

R12

C6 39K

6N8

C11

REVERB LEVEL

R27 2K2

R18 100u

C10

R29

R30 47k 1M

f1 f2

C13

R32

1K

R28

2 3 U1A TL072

10K -5V

470K

1M

C5 R15

+5V

100N

C16

100N 1

4 1 5 2 3 6

4

J2 R24 56K

68N

C8

1MLIN

10N

Vin

U2 BTDR-1H

100N

+5V C14

8

8

VOUT

Vb

ECL86

1

1

R35

1K R37

10K

C12 100N

9

9

100N

C9 100N

R16 470K

R8 470K

C2

R4 100K

2

Date:

Size A4

Title

10K

10K

R39

R38

SET MAX. REVERB

R3 1 V2B 100K

V3B ECL86

470K

470K

R25

R7 820R

R2

TREMOLO/REVERB SW

R20

470K

100K

C15

R33

C3 10N

TREMOLO SPEED

R11 680K

R14

R22

10N

TREMOLO DEPTH

15N

115K

1K R23

820R

R19

8

7

R9 470R C4

6 ECC83 V1B

100N

R31

100K

1ECC83

3 4 9 5

TONE CONTROL

500K LIN

R13

2

V1A

R5

VOUT2 2

7

Vcc

C1

GND SIG 3

D

GND PWR 5

R1 220K

4 8

3

N.C. 6

Vb

+

4

R34

U1B

TL072 7

115K

Va

Vg2

V3A 7

3

3

ECL86

6

6

7 ECL86

Vg2

T1

5

4

1

1

TP2

TP1

Friday, November 28, 2014

2013-35-A

Document Number

1 BRN A1 2 RED CT 3 BLU A2 4 BLK 8 OHMS SEC 5 GRN 8 OHM SEC +

Sheet

1

of

2

Rev A

speaker 8 ohms+

speaker 8 ohms-

Hammond 1750E pinouts

OPT HAMMOND 1750E

3

2

1

© 2014 Bergqvist Copenhagen

R40

5

2 4

10k

10K

R36

f2

f1

R21 1K

100u

C7

V2A

1

The Shrimp Personal Guitar Amplifier

5

6

4 2

5

R10 125R

R6 1K

f2

f1

+

-

-

5

A

B

C

D

The Shrimp – Personal Guitar Amplifier Illustrations:

Figure 35-1 Amp schematics

395

The Shrimp – Personal Guitar Amplifier Illustrations:

Figure 35-3 PCB

397

Index

Index Symbols 1N4007 150, 335 6HZ6 375 6J5 166 6L6 287, 401 6L6GC 49, 65, 112 6SN7GT 66, 83, 107, 166 6V6GT 83, 101, 109 807 65 812A 81, 83, 84, 86 5881 112 14066 CMOS switches 239

A A/B recording 343 absolute linearity 264 A/B stereo 350 A-B stereo output 367 AC and DC symmetry 171 AC balance 108 AC mains frequency 204 Acoustical Quad 147 Acoustics 187 AC signals 425 AC symmetry 429 Active Compressors 374 AES 128 AF amplifier 71 AFEH 187 air gap 71 AM modulation 390 amorphous magnetics 302 Ampeg SVT 427, 431 Amperex 32 Amplifier noise 302 amplifier stage 65 anode supply voltage 158 asymmetrical electret mike 359 ATA drives 71 Attack slope 373 Attack time 373 audio signal 125 Automatic Gain Control 375

B balanced amplifier 147, 301 balanced input signal 107 balanced microphone 301 balanced negative feedback 147 balanced power amplifier 313 Balance pots 127 balancing potentiometers 167 banana sockets 88

bandwidth limitations 170 Bass Booster 288, 411 Baxandall 239 Baxandall circuit 126 Baxandall tone stack 264 Bessermachen 207 bi-amping 126 Bias adjustments 151 bias voltage 357 BLUBOTTLE 27 Bluebottle Amplifier 240 blue smoke 81 Blue Smoke syndrome 85 bobbin 231 boosting amplifier stages 304 burst oscillations 165 Butterworth filters 128 butterworth high-pass filter 101 Butterworth low-pass filter 102 BUZ50 85

C capacitive coupling 129 capacitively coupled feedback 147 capacitors 48 carbon composite resistors 263 carbon resistor 87 Carbon track trimmers 384 Carbon-track trimmers 109 Carbon trimpots 150 cardioid 363, 364 cascaded amplifier stages 211 cascode 28 Cascodes 207 cathode 49 cathode circuit boosting 400 Cathode feedback 174 cathode follower 65, 351 cathode resistor 107, 149 Cathode resistors 88 Caviar 71 Caviar amp 71, 73 CD4047B 72 center microphone 365 cermet trimpot 303 channel amplification 125, 291 charging caps 88 charging currents 322 choke 84, 167, 173, 231, 265, 289, 385, 401 circuit complexity 84 cocktail ear 315 COL 128 cold cathode tube regulator 150 compensation parameters 240 Complex loads 165 Compression level 373

435

The Bottle Builder: A Compendium of Tube Amp Designs vol. 1 Compressor 411 compressor circuit 412 condenser capsule 357 condenser microphone 351 cone exertions 110 constant-current amplifier 147 Constant Current Cathode Contraption 323 Constant Current Source 171 Continuo II 409, 412, 415 conventional pentode stage 206 Conversion circuits 304 Cooling Fins 268 copper screen 231 copper windings 66, 84 Core size 71 counter-electromotoric forces 106 Coupling capacitors 29, 267, 303 Creeping distances 87 crosschannel 84 cross-coupling 277 Crossfeed 187 Crossfeed Circuit 190 crossover capacitor 101 crossover filters 291 crossover module 125 current diode bridge 86

D Damping Factor 50, 105 DC balance 108 DC balancing 189 DC coupled 107 DC coupled input 166 DC current 83 DC heating 86, 130, 191 DC leakage 351, 412 DC motors 301 DC offset points 189 DC resistance 351 Decay slope 373 Decay time 373 decoupling 50, 102 decoupling capacitor 172, 264 de-emphasis circuit 209, 303 dielectric properties 87 differential signal 349 digital high power output 427 digital multimeter 88 digital signals 246 diode switching noise 344 Distributed Load 168 Dolby 16, 147 driver 50 driver stage 83, 147, 169, 287 driver voltage 84 dual triodes 291

436

Dynaco amplifiers 168

E E80CC 83, 85 E84L 27 E88CC 303 E130L 101, 159 E188CC 207 E282F 102, 160 ECC81/12AT7 126 ECC82 83, 109 ECC83 101 ECC801S 126 ECL82 73 ECM2000 358 EF86 129 EF804S 129 EICO HF-87 335 EL34 112, 428 EL95 149 Electret Microphones 357 electrolytic 109 electrolytic capacitors 159 electrolytic caps 112 electromagnetic transducer 208 electronic crossover filter 127 elliptical diamond stylus 238 EM71 151 EM84 29 EM800 29 EMM800 102 EMM802 73 enamelled copper wire 87, 231 encoder 49 EQ 416 EQ pots 412 equalizer 412 equal-loudness curves 316 errite inductors 106 ESL electrostatic speakers 238 extreme linearity 82

F Fairchild 670 373 feedback 32 feed-through filter 111 Fender 16 Fender Stratocaster 399 Fender Telecaster 391 ferrite HF killers 109 FET 324 FFRR 203 FFSS 128, 203 figure-of-eight sensitivity 364 filament transformer 82 filament voltages 206

A COMPENDIUM OF TUBE AMP DESIGNS

THE BOTTLE BUILDER Johan Basse Bergqvist

This book is intended to be a hands-on recipe collection of my amplifier designs over more years than I care to remember. There is little emphasis on the scientific explanations nor discussions and the designs can be built by anyone if the instructions are followed.

You are about to embark upon an endeavor from which there is no return; some audio aficionados insist, that sound lost during digitalization is present in the grooves of a vinyl record. They just may be right: Life is analog.

Engineer, musician and writer, Johan Basse Bergqvist is in lifelong pursuit of perfection in arts, sound and life. He is blessed with a loving family and many opportunities to do what he likes most: building things – because they needed to be built.

ISBN 978-1-907920-38-7

© Elektor International Media BV 2015 159001-1/UK

The same aficionados, this time aided and abetted by audio desperados, equally persist in believing, that only with tubes the absolute Nirvana in sound reproduction can be achieved. Who am I to contradict – and this is what this book is all about.

The first time you have enjoyed the spectacular results of your homemade tube audio you have also shared the Opium known as HiFi with the rest of us addicts. You have been cautioned. Several of my esteemed fellow writers have indeed published welldocumented scientific documents, designs and opinions based on fact and I am not knocking their contributions.

The more successful designs are compiled in this book ranging from extreme high fidelity to instrument amplifiers producing the desired level of harmonic distortion coveted by my fellow musicians and myself.

Music and HiFi appreciation is very much a combination of basic abilities and learning.

Musicians and professional listeners like conductors and studio engineers do not utilize the same part of the brain for listening as non-musicians and the average layman do.

This is fact. Analytic listening is an acquired skill that can be learned.

Some of the gurus of the past like D.T.N. Williamson, Stanley White and other pillars of society did not always get their math right and some classic designs could use a little improvement. A few like Peter Walker (Acoustical Quad) had the ability to think out of the box during a time, when HiFi was buzz-word and not really defined, standards were defined by every individual manufacturer and loudspeakers pretty much designed by instinct (pre-Thiele/Small). Revision of some of the classic designs is part of this book too and a product of my affection for perfect sound reproduction and ultimate performance of electric instruments.

This is not an audio bible, a lecture on gospel or a revelation. You are already past that since you read this. You are tired of commercial products and seek salvation – I humbly show you the path to it.

● SHARE ● LEARN ● DESIGN ● SHARE ● LEARN ● DESIGN ● SHARE ● LEARN ● DESIGN ● SHARE ● LEARN ● DESIGN ● SHARE ● LEARN ● DESIGN ● SHARE ● LEARN ● DESIG RE ● LEARN ● DESIGN ● SHARE ● LEARN ● DESIGN ● SHARE ● LEARN ● DESIGN ● SHARE ● LEARN ● DESIGN ● SHARE ● LEARN ● DESIGN ● SHARE ● LEARN ● DESIGN ● SH ARN ● DESIGN ● SHARE ● LEARN ● DESIGN ● SHARE ● LEARN ● DESIGN ● SHARE ● LEARN ● DESIGN ● SHARE ● LEARN ● DESIGN ● SHARE ● LEARN ● DESIGN ● SHARE ● L N ● SHARE ● LEARN ● DESIGN ● SHARE ● LEARN ● DESIGN ● SHARE ● LEARN ● DESIGN ● SHARE ● LEARN ● DESIGN ● SHARE ● LEARN ● DESIGN ● SHARE ● LEARN ● DESI ARE ● LEARN ● DESIGN ● SHARE ● LEARN ● DESIGN ● SHARE ● LEARN ● DESIGN ● SHARE ● LEARN ● DESIGN ● SHARE ● LEARN ● DESIGN ● SHARE ● LEARN ● DESIGN ● S ● SHARE ● LEARN ● DESIGN ● SHARE ● LEARN ● DESIGN ● SHARE ● LEARN ● DESIGN ● SHARE ● LEARN ● DESIGN ● SHARE ● LEARN ● DESIGN ● SHARE ● LEARN ● DESIG RE ● LEARN ● DESIGN ● SHARE ● LEARN ● DESIGN ● SHARE ● LEARN ● DESIGN ● SHARE ● LEARN ● DESIGN ● SHARE ● LEARN ● DESIGN ● SHARE ● LEARN ● DESIGN ● SH