[sdiy] Oberheim SEM module

[john mahoney]

I'd suggest that your friend look at the OB-X voice card schematics to see
what came after the SEM. It's "the same but different," as some people
say -- the next version of the same basic circuits. For example, the SEM
uses 741 op amps paired with FETs whereas the OB-X uses TL081s or TL082s
(which have built-in FET buffers, if I've got my facts straight).

The OB-X has CA3080s all over the place to provide for programmability, but
they also present additional VC possibilities. These 3080s are used like
voltage controlled resistors.

The OB-X uses Curtis CEM3310 envelope generator chips for the ADSRs.

24dB filters didn't appear on Oberheims until the OB-Xa or OB-8, which used
Curtis VCF chips.
--
john