Western Electric 1930s-1940s
Western Electric 1930s-1940s
Western Electric 1920s
German Broadcasting 1940s
German Broadcasting 1940s
RCA BA-1A from 1945
1940s - 1950s
Langevin 1947
Siemens & Halske 1952
Siemens & Halske 1952Modified by G J Cohen 1996
Radiotron Designer’s handbook 4th ed. P789
Radiotron Designer’s handbook 4th ed. P790
Radiotron Designer’s handbook 4th ed. P791
AWA Consolette.
Courtesy Phil Punch, Electric Avenue Studios
AWA Consolette.
Courtesy Phil Punch, Electric Avenue Studios
Radiotron Designer’s handbook 4th ed. P792-793
Altec M11 system 1950
Altec M11 system 1950
Morgan Jones 1995
AKG C24 microphone
Treharne 1958
Langevin AM16 1961John Hall is credited with this design, and he subsequently left Langevin and went toAltec where his name can be found on the similar PP 9470A/9475A amps of 1964.
Langevin AM16 1964
1972
Bailey. Wireless World
Graeme J Cohen. Sept 1984
Graeme J Cohen. Sept 1984
Graeme J Cohen.
Hybrid Input Concept
Graeme J Cohen. Sept 1984 Double Balanced Microphone amplifier
AES preprint 2106
Graeme J Cohen. Sept 1984 Double Balanced Microphone amplifier
AES preprint 2106
1 2 3 4 5 6 7 8
A
B
C
D
87654321
D
C
B
A
Title
Number RevisionSize
A3
Date: 7-Aug-2008 Sheet of File: D:\CLIENTS\COHEN\DUALMI~1\PCB\AMP22.SCHDrawn By:
R16K8 1/2W
D136V 1W
R21K
R533K
VR1
10K
D2
1N4004
+48
OM1556 Dual Mic Amp 2006
I. DuRIEU
2.2
240V AC
1 1
I
A
O
U5LM317T
C1
1000uF 35V
C2
1000uF 35V
D31N4004
D41N4004
T116V AC 1A plug pack
C7
330uF 63V
C8330uF 63VD5
1N4004
D61N4004
Nom +70V
I
G
O
U1
LM7918
I
G
O
U2
LM7818
D7 1N4004
D8 1N4004
+18
-18
+18
-18
H3RED 3mm
T2BC548
T3BC548R3
1K
R639K
R8220K
R103K9
R121K6
C92u2 50V BP
C11100uF
Nom +25VH1Blue
C13
10uF
C14
10uF
C15
0.1uF
1
2
3
6
7
8
910
11
12
+in
-in
+G
E
-GRI
VEE
VCC+out
-out
U3OM1556
12345 6 7 8
9101112
CSW1SW-12WAY
12
3
SW3A
87
9SW3C
Nom -25V
C12100uF
D9BAT85
BR1W04
+18
+18
D10BAT85R14 open
R15 750RR16 270RR17 130RR18 68R R19 11R0
R20 12R
R23 1R0
R24 36R R25 20R
R276K8 0.01%
R29 1K5 0.01%
R301K5 0.01%C16
220uF 50V
C17220uF 50V
C181uF MKT
C191uF MKT
cable toinput XLRs Cable to
output XLRs
R286K8 0.01%
**
**
**
** **
Matched
R31
10R + 2 beads
R32
10R + 2 beads
Power
Power LED also providesmin load for LM317
R33
12KH2Yellow
45mA max
C20
0.1uF
R263K3
R34
270R
R35
270R
12
3SW2A
+48
Phantom
LNK1
P48 Enable
12
3
SW4A
87
9SW4C
Phase Reverse
50/600 Ohms O/P Z
BR2W04
+18
-18
C21
0.1uF
LpkLED
LpkLED
Left PEAK LED
+18
-18
H4RED 3mm
T4BC548
T5BC548R4
1K
R739K
R9220K
R113K9
R131K6
C102u2 50V BP
RpkLED
Right PEAK LED
Gain
Bolt1Bolt2Bolt4C27
0.1uF
Bolt3
220uF 50V Farnell 876-7424Panasonic ECA Series
All 3 regs on vertical 24 C/W sinks
X8 X9
Sub boardAll buttons are drawn in the released position
45
6
SW2B
Multiple switch sections are in parallel
45
6
SW3B
11
1210
SW3D
45
6
SW4B
11
1210
SW4D
12
3
SW9A
87
9SW9C
12
3SW8A
12
3
SW10A
87
9SW10C
12
3
SW11A
45
6
SW8B4
5
6
SW9B
11
1210
SW9D
45
6
SW10B
11
1210
SW10D
45
6
SW11B
C3
1000uF 25V
C221uF MKT
C4
1000uF 25V
C5
1000uF 25V
C231uF MKT
C6
1000uF 25V
R36100K
R37100K
1000uF 25V Farnell 876-7297Panasonic ECA Series
X10X12
12
3
SW5A
Ground Lift
45
6
SW5B
LNK2
LNK3
LNK4
**
**
LNK5123
X2
3PIN123
X3
3PIN
Sold
er p
ads 30dB
25dB20dB15dB10dB6dB
35dB40dB45dB
50dB55dB
60dB
R38 12R
R39 3R3R41 1R8
R43 22R
(6R0)
(0R958)
1
2
3
6
7
8
910
11
12
+in
-in
+G
E
-GRI
VEE
VCC+out
-out
U4OM1556
12345
6 7
89101112
CSW6SW-12WAY
D11BAT85
BR3W04
+18
D12BAT85R44 open
R45 750RR46 270RR49 130RR50 68R R51 11R0
R52 12R
R60 1R0
R61 36R R62 20R
R636K8 0.01%
R65 1K5 0.01%
R661K5 0.01%C32
220uF 50V
C33220uF 50V
C341uF MKT
C351uF MKT
cable toinput XLRs Cable to
output XLRs
R646K8 0.01%
**
**
**
** **
Matched
R67
10R + 2 beads
R68
10R + 2 beads
R69
12KH5Yellow
R703K3
+18
+48
Phantom
C38100pF
C39100pF
LNK6
P48 Enable
BR4W04
+18
-18
RpkLED
Gain
220uF 50V Farnell 876-7424Panasonic ECA Series
X4 X6
Sub board
All buttons are drawn in the released position
Multiple switch sections are in parallel
C28
1000uF 25V
C411uF MKT
C29
1000uF 25V
C30
1000uF 25V
C421uF MKT
C31
1000uF 25V
R71100K
R72100K
1000uF 25V Farnell 876-7297Panasonic ECA Series
X5X7
Ground Lift
LNK7
LNK8
LNK9
**
**
LNK10123
X11
3PIN123
X13
3PIN
Sold
er p
ads **
**
30dB25dB20dB15dB10dB6dB
35dB40dB45dB
50dB55dB
60dB
R53 12R
R55 3R3R58 1R8
R73 22R
(6R0)
(0R958)
D131N4004
D141N4004
Phase Reverse
50/600 Ohms O/P Z
****
R47
270R
R48
270R
****
Solder pads
123
X1
3PINScreened power cable
** **
** **
C24100pF
C25100pF
C26100pF
**
**NPO
NPO
NPO
NPO
NPO
NPO
C40100pF
(330mW)
OM1556 designed in 1984
1990
1997 - 2006
Graeme J Cohen. Sept 1996
Split Cascode Amplifier
AES preprint 4296
Dual OM1556 2006OM1556 designed in 1984
Dual OM1556 2006OM1556 designed in 1984
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