Or, maybe not even that. It might have used something like a piezo. Or it may not have been a DRUM at all. It may have been a module. Who knows? I’ve never seen one.
I read this thread with interest as I have recently picked up two 701 (drum synth) and two 702 (percussion synth) modules.
The 702’s are incomplete, never finished… but I have had the 701’s fired up… 
http://www.youtube.com/watch?v=S_YAtUR6gG4
https://www.youtube.com/watch?v=ck2gN-eUZKA
Hope you like them… they are quite interesting things…!
Cheers,
Tomto
I read this thread with interest as I have recently picked up two 701 (drum synth) and two 702 (percussion synth) modules.
The 702’s are incomplete, never finished… but I have had the 701’s fired up…
http://www.youtube.com/watch?v=S_YAtUR6gG4
https://www.youtube.com/watch?v=ck2gN-eUZKA
Hope you like them… they are quite interesting things…!
Cheers,
Tomto
Hey Tomto!
Welcome aboard! I watched those vids from Matrixsynth the other day. Excellent!
Those Moog drum modules are indeed rare. So cool to actually hear one playing too, great job. So is there any chance to get some high resolution photos of the circuit boards inside the 701? I know these are made with the Vector Plugboard, but it would be a great opportunity to document these. AFAIK there is no circuit diagrams, or much info out there on any of these.
Seems to be a real loss that these were never published, as they were probably one of the first drum synthesizers made. And designed by Bob Moog himself. Anyhow, if you could shed any light on these rare undocumented Moog modules it would be greatly appreciated. It would be great to be able to clone these. Probably some rare parts though.
It also looked like your Moog has a 901C Output Stage module? Any chance to get a photo of the circuit board on that one too? I have successfully made a clone of that for my Moog, but would like to see what an original looked like. Only 15 of those 901C modules produced. (Plugboard?)
Thanks much if you can get some clear photos of the circuts! And good luck with those modules. Great to see them being used.
Wimp!!
Then again, I had that Audity in my apartment for a year* and the owner wouldn’t let me power it up either.
It’s kind of hard to fix something if you can’t even power it up, you know?
Nice decorator item anyway. 
[/quote]Thanks much if you can get some clear photos of the circuts! And good luck with those modules. Great to see them being used.[/quote]
I shall try sir!
By the way, that photo of Bob using the eight 701’s - of which I now have two (the museum having the other six) - it seems I also have that headphone monitor Bob is using there. There’s a load of prototypes in my system… there is a 901b oscillator casing, with completely unknown innards..! Maybe Kevin could identify it, if I send him some photo’s..? Also my 905 reverb is built on that prototype board… and there is a VCA case with some kind of distortion unit, it has a microphone input with 5 or 6 different outs.
And that’s not all… there is a photo here: http://musicthing.blogspot.co.uk/2006/04/island-of-electronicus.html
That sign there in the background behind Bob… “R.A.Moog Synthesizer” - I also have that…!
And that’s not all… there is a photo here: http://musicthing.blogspot.co.uk/2006/0 … nicus.html
That sign there in the background behind Bob… “R.A.Moog Synthesizer” - I also have that…!
Thats bad ass right there, also congrats on the super rare drummodules.
Did i stumble on your facebook somehowe..?. Bring back the…?
love to get me a RA modular someday… dream onnn, dream away… i think i bla bal bla
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.
Two other source might have info - Audities.org or MoogArchives.com. I know that both have documents from the RA Moog days.
Good guesses CZ.
Unbelievable!
This just showed up today on the BMF site.
Bob’s schematic drawing of the #1 board VCO/CVF/VCA of the 701.
And there it is! Well half of it. My guesses were close, three saw core VCO’s, a two pole LPF and VCA.
And my guess was spot on that the BMF has these schematics they should be sharing with the synth community. AFAIK this is the first time these drawings of the 701 have been shown to the public.
I still want to see the drawings for the Red Noise Filter.
I am currently cloning the 901C and wanted to add the “Modulation Mix” pan pot the Minimoog has for added function. I have the schematic to filter the 903 white noise to pink, but I have to guess on the red noise filter. A drawing from Bob would make it so much easier and correct.
They posted another drawing. Had to study it a little, very low resolution pic of the drawing. Looks to be the component layout on the second 701 board with the envelopes.
(Drawing below with pic of the board I pasted above.)
I’m finding this newly released info very interesting. I could almost make a 701 clone from these bits of info. I like the way Bob drew the components out for the Plugbaord. Never saw these kind of drawings from Bob before. A higher resolution scan of all the pages/notes Bob kept would be all that is needed. I’m sure Bob kept similar type notes for all these early modules.
Somewhere out there is all this missing info on these and other unique modules Bob designed. Like the 901D Variable Output Stage. Probably a hand drawn set just like the 701 drum module, with schematic and layout. Then there is the 902-A Band Pass Filter Adapter, 906 Impulse Generator, 913 Triggered Envelope Generator, and that 702 percussion module.
Would be fun to have a look at these!
You sound excited, CZ.
Are these patented or public domain or what?
The 701 is an old prototype design from 1969. Some of those parts are hard to source, a few transistors and those CL-1 diodes.
Just seems funny for all these years the 701 and 702 modules were one of those Moog mysteries. No one really knew anything about them, other than they were used for the historic “Jazz in the Garden” concert. And a custom system was sold to Eric Siday. Most recently Tomto posted the first ever demo of a working 701, and some photos of the circuit boards. And now the actual schematic/drawings Bob drew out appear?
Anyhow this was probably the first ever synthesized drum/percussion modules ever made. Doubt there was ever any patent applied for. The 702 is still a mystery. With the “excitation” section using “repition” and “regularity” knobs, one can only guess what this did. For drum rolls?
But I am fascinated with those early transistor designes Bob came up with, and that Vectorboard they used, very 60’s. Have been trying some of my own. Here is the 901C board with room for the pink and red noise filter. Using that same method of Vectorboard with the little pins and 22 pin edge card. A Moog S-trig to V-trig converter below.
It would be fun to make some of those 701 drum modules.