Interesting modules. Have had a little time to listen to the demos and figure out what those cryptic abbreviations are on the rotary selectors in the modulation and auxillary source.
So watching the 701 demo video, it dawns on me there is no noise source. Noise is a big part of many synthesized percussion patches. Looking at the large 700 percussion system, there is a 903 White Noise Source module. And next to it a filter for the white noise, to get pink and red noise. Guessing the white, pink and red noise would be routed to each 701 in the system via the rear 22 pin edge connectors. This makes sense as you really only need one noise source with the various colors for all those percussion/drum modules.
Realizing this, those abbreviations and those sections now made a little more sense guessing what they were for. So the auxillary selector 1) EXT. for the external socket audio input. 2) P.N. for pink noise. 3) W.N. for white noise. With the amplitude dial to mix in this auxillary audio source, along with the three oscillators to get your percussion sound. Really needs that audio noise source to make snares and cymbal tones.
The modulation section selector would be 1) EXT. external socket for a mod source. 2) R.N. for red noise. 3) P.N. for pink noise. 4) OSC1 for oscillator 1 as the modulation source, with the Modulation Width dial for modulation intensity. A little surprised there was no modulation from the envelope section, to get that familiar "Disco" sound. But in a modular system, all that woud be needed is an extra 911 triggered envelope patched into the EXT. input socket to modulate the oscillators that way. Could see in the demo when the selector went from osc1 to the other sources, there was no modulation without the noise source connected.
Here was the noise modules for that system. Any 903 or 903A would work, but I would like to see the schematic for the red noise filter. (100Hz lowpass filter.)
The rest of the functions is a guess. Does not seem to have a typical 4-pole ladder from the demo and no, or fixed resonance. With the envelope section still a bit of a mystery. The filter section sporting an attack decay envelope with a reversable attenuator. The VCA envelope with the unfamilliar decay 1 and decay 2 with a decay proportion? Would have to play around with that to figure it out. The demo seemes to have a switched gate. An LFO pulse triggering the 701 may have revealed a bit more about those envelopes.
Tomto was nice enough to send some pics of the circuits. Thanks Tom!
Here are some cropped pics of the 701.
701 back.
Can see the 4 input resistors to mix the 3 osc and aux. source.
701 circuit right side. (2 envelopes, rev attenuator?)
Can see the many connections made on the edge card, trigger, white/pink/red noise, audio out, and power.
701 circuit left side. (3 oscillators, filter, VCA?)
The left side looks to have three identical oscillators. Guessing just the sawtooth core, no waveshaping. Very simple. Above looks like 3 sets of transistors and two caps to form a two pole ladder filter. With possibly a mixer/VCA on the same row behind the filter. Any one want to guess? Not enough info here to reverse engineer, but enough info to guess the basic layout.
The right side is a little more intense and seems to be the envelope generators and reversable attenuator circuit. Don't see those 2N4303 JFET type the 911's used. More like a Mini style envelope using descrete NPN/PNP transistors. Any guesses?
Would like to see the schematics for these or at least some design notes. This is what I wondered might be in those many file boxes from the R.A. Moog Co. days in Bob's archives. This predates the Minimoog and I see a few things in common that may have been borrowed for the Mini, like the pink/red noise modulation source.
1P Modular,Minimoog,VoyagerRME,CustomMinimoog,Prodigy,MG-1 TaurusII,Opus3,Rogue,Source,Liberation,Micromoog,1125S&H,
1130Perc.x2,1150Ribbonx2,Custom1150,1120Pedal,Songprod,CP-251,VX-351
VX-352,Etherwave,Synampx2,Lil'Phatty,Sonic Six
