The following are presented for educational/historic purposes only and are not to scale. These designs are copyright Serge Tcherepnin.

Some info on the 1973 variant of the ring modulator / gate (VCA) module:

• overlay and pcb pattern
• pcb pattern
• photo/overlay
• Ring modulator schematic
• Gate schematic
• Sergé's famous letter on OTAs and their relationship to his ring modulators. Reproduced here with the permission of Bernie Hutchins.

PCB connections:

Ring
A
B = VC X
C = Y
D = VC Y
E = X
F = Out

VCA
A = CV lin in
B = CV log in
C
D = DC sig in
E = AC sig in
F = Out

U = not used (0v)
W = 0v
X = +12v
Y = +6v
Z = -12v

Classic Serge