What is the difference between the CP3 (circa 1968) and the CP3a (console panel format with the voice switches). And I’m really most interested in the mixer circuit portion of it, the form factor and jack layout is obvious.
I found an old thread (courtesy of Kevin) which answered some of my questions (“click” aspect); A historical recount of each would be great if M.Doty or CZ have this, super.
Thank you.
The CP3 would be discrete mixing circuit.
CP3a initially was discrete, later changed to opamps.
Ah… found this; it’s all here (in case somebody else is interested): http://www.muffwiggler.com/forum/viewtopic.php?p=1173860
This is all true, however the outcome of this is that 3As can provide outputs with more drive capability, slightly higher gain and.. arguably… lower noise and faster slew rates.
They can also accept hotter inputs and produce hotter output signals, especially negative.
3As a’re not as easily overdriven therefore, which is subjectively a feature for a plain 3 (not 3A) because distortion can be a valued asset when desired.
Functionally they look and operate pretty much the same though.
That’s interesting to think about. The rest of the Moog system still uses the +12/-6 power supply. While all the other CP modules in a Norlin era system uses the +/-15 supply. (CP3A, CP4A Rev. Attenuator and Filter CV summer, Trigger buffer, Accessory socket.)
Even though the CP3A might not distort, every Moog module you send this signal will, above a certain threshold. Any gain in headroom is going to be lost unless the CP3A is patched as the final output module. So with a CP3A, a clean un-distorted mixed signal that is hot enough will drive a 904A/B VCF or 902 VCA into distortion, especially on the negative side. Very interesting! Might have to try that to see how many different sonic possibilities there are with this. The CP3A might have less of a tendancy to distort, but it seems you can hit a Moog VCF/VCA harder than any other module in a Moog system using the +12/-6 rails.