A
B
C
D
E
SUPPLY DECOUPLING FILTER R1
233VDC
2
1
1
1
10K/1W
C1 50uF/450V
R3 75K
P R E AMP STAGE 2
2
P R E AMP STAGE 1
OUTPUT STAGE
TONE CONTROLS C3 1
BLUE/RED*
2
BROWN/RED*
PENTODE
EL84
R2
244VDC VR2
2
470K 8
1MEG LOG
3
2
1K/1W C2 50uF/450V
1
MIDDLE
3
2
3
2
R15 130/1W
25K LIN 0.022uF
P O W E R TRANSFORMER
Note: Change R2 to 10K to use Svetlana S V 83 instead of EL84 output tube. EL84 will still work in modified circuit, just at slightly reduced gain.
1
VR4
2
C10 100uF/25V 2
C9 2.2uF/25V
1K
2
2
R14
2
0.1uF
1
1
1
VR3 1MEG LOG
C8 2
C7
2
1
2
R13 1.5K
0.85VDC
6.9 VDC
1
VOLUME
1
1.1VDC
R12
2
BASS
3 1
1
3
1MEG
1
2
68K PHONEJACK
8
3
4
2
J1 1
SW 3POS
2
PHONEJACK
SW SPDT
1
12AX7A
2
YELLOW/LT GREY* B L A C K /DK GREY*
4
3
0.022uF
12AX7A
7
2
V2A
R21 2
0.005uF/1500V
2
1
1
1
6
V2B
R9
2 1K/1W
5.6K
TREBLE
3
C6 1
1
5 6
16
1
1
239VDC
2
3
143VDC 2
0.01uF
2
VR1 250K LIN
2
2
INPUT
9
1
O R A N G E / Y EL* GREEN/ BLUE*
OT-5SE
2 C4 1
R8 2
0.01uF
U1
R7
1 R6 33K
C15
4
S1 3 4
C14
TRIODE
1 1
1 2
R5 27K
159VDC
7
V1
470pF
100K
J2
1
2
R4
S P E A KER OUTPUT
T1
1
1
167VDC
IMPEDANCE SELECTOR
OUTPUT TRANSFORMER
2
4
BIASING: :EL84 max bias current is 48mA as measured in plate lead, or approximately 53mA as measured across R15 in cathode lead. Do not exceed 12W dissipation as calculated by: (Vplate - Vcathode)*Iplate. Screen current can be subtracted from cathode current to find exact plate current by measuring the voltage drop across R7 and dividing by its value (1000 ohms). Bias current can be adjusted by changing the value of R15. Lower values of resistance yield more bias current, and higher values yield less bias current. Cathode current is equal to cathode voltage divided by cathode resistance R15.
3
OPTIONAL SOLID-STATE RECTIFIER
POWER SUPPLY FILTER
RECTIFIER
*Note: output transformer color code: first color is for the Aiken output transformer, second color is for the Delft output transformer.
D1 T2
4 RED/YEL
FUSE S4
F1
BLACK
2
1
3
1
1
4
2
TO C11-1/R16-1
1
1N4007 (OPTIONAL)
100/1W
2
250VDC
2
D2
C12 50uF/450V
FROM T2-5
2
1
1N4007 (OPTIONAL)
RED EZ80/EZ81/6CA4
115VAC
4
C11 50uF/450V
190VAC 5
1A SLO-BLO
7
1
S5
SW SPST (OPTIONAL)
1
AC MAINS
STANDBY
R16 3 5
1
190VAC
2
2
P O W ER SWITCH
V3
2
2
FROM T2-3
RED
1
3
V4
(Standby switch is recommended for solid-state rectifier)
V5
5
If standby switch is not desired, ground T2-4. 6
12AX7AFIL 5
EL84FIL 4
POWER CONNECTOR
9
2
4
BLACK
SW DPDT
5
6 J3
GREEN
6.3VAC
1
N o tes:
R17 100
All resistors 1/2W minimum unless otherise noted.
1
1
FILAMENT HUM REDUCTION/BLEEDER RESISTORS
$;
R19
50VDC
R20 47K
2
7KH &RRSHUDWLYH 7XEH *XLWDU $PS 3URMHFW
180K C13 22uF/100V
Title
Size
50uF/450V electrolytic power supply capacitor values/voltages are not critical. Suggested values: 20-50uF at 350-450VDC.
Date: A
B
1
http://www.intsys.net/ax84 _______________________________
2
All voltages are PSpice simulation results based on 250V plate supply. Actual voltages may vary.
R18 100
1
Hammond power transformer voltages specifed for 115V input. Secondary voltages will be higher with 120V input.
2
All coupling capacitors 250V or greater.
2
1
1
GREEN
H A M M O N D 2 6 9 EX
2
7
C
D
AX84 Amplifier Document Number
Rev 10
November 1, 1998
Sheet E
1
of
1