Buchla - CV vs Audio

Have you ever wondered why Don Buchla separated control voltages from audio signals.

In virtually every other modular synthesizer system there is no division between the two.
Eurorack use 3.5mm cables.
Serge use Bananas
Moog and the rest of the 5U community use 1/4 inch jacks.
This democracy of connectors seems very practical. All voltages are treated the same and this gives increased flexibility and scope for experimenting.

So why did Don decide to separate the two

I just read an old interview of Don Buchla which may shed some light on the subject.
http://www.vasulka.org/Kitchen/PDF_Eigenwelt/pdf/096-099.pdf

"I would say that philosophically the prime difference in my (Don Buchla) approach from that of Robert Moog was that I separated sound and structure, and he didn’t. 

Control voltages were interchangeable with audio (in the Moog world).  
The advantage of that is that he required only one kind of connector and that modules could serve more than one purpose. 

There were several draw-backs to that kind of general approach, one of them being that a module designed to work in the structural domain at the same time as the audio domain has to make compromises. DC offset doesn’t make any difference in the sound domain but it makes a big difference in the structural domain, whereas harmonic distortion makes very little difference in the control area but it can be very significant in the audio areas. 

You also have a matter of just being able to discern what’s happening in a system by looking at it. If you have a very complex patch, it’s nice to be able to tell what aspect of the patch is the structural part of the music versus what is the signal path and so on.  

There’s a big difference in whether you deal with linear versus exponential functions at the control level..."
D.B. 1964.

The last point raises questions re linear vs. audio taper, bipolar vs. unipolar, and shielded vs. unshielded cables.

Another article from SOS shines more light on the subject:

"One significant difference between Buchla's approach and that of Bob Moog was his separation of the signals used in synthesis into three distinct classes. 
First, there were the audio signals, which could be generated by oscillators, or injected into the system from devices such as microphones or tape machines. 
Secondly, there were the control voltages. 
Finally, there were timing pulses, which we nowadays call clocks, gates, and triggers. By today's standards, the audio levels were quite low (about 1V peak-to-peak) and the CVs and pulses were rather hot, with a maximum voltage of around 15V."
 http://www.soundonsound.com/sos/dec05/articles/buchla200e.htm


The precise  Buchla audio & CV levels fluctuated over the decades:
100 series Buchla had audio at 0dBV .... roughly 1 volt RMS.
Pulses are 15V and CVs range between 0V & +15V.
Early 200 series Buchla used audio levels of +4dBV... Professional line level  of +1.736 RMS
Pulses are 15V and CVs range between 0V & +15V. for early 70's 200.
Late 200 Buchla  dropped the CV range to 0-10V. Audio levels stayed the same at +4dBV
Buchla 200e dropped audio back to 0dBV. Pulses are 10V. CVs are 0 to +10V.

Inspite of these changes over time, one thing remained constant : the huge gap between CV and  audio levels. It's probably a good  enough reason for not mixing  CV and audio (or at least taking extra care) within a Buchla system .

This is making me wonder what the compatibility of the new RED Panel Buchla 100 will be like with my standard Buchla. I'd love to mix the two if that was possible. It's interesting that this separation of CV & audio is gone within that system. I guess this makes it more compatible with Eurorack.

According to the Doepfer manual, the Eurorack universe runs by these guidelines:
Audio voltages produced by modules such as a VCO or NOISE are typically in the 10Vpp range (from -5 V to +5 V)
Control voltages, as produced by modulation sources like a LFO and ADSR, are typically from -2.5 V to +2.5 V (5 Vpp) for LFOs, and from 0 V to +8 V for ADSRs.
These days, there are lots of companies that have +/- 5V CV ins and outs. (10Vpp)
Trigger, Gate or Clock Signals, are typically rectangle shaped signals with voltage levels of 0/+5 V

Synovatron make an excellent series of modules that do Buchla- euro & Euro - Buchla conversions easy.
https://www.muffwiggler.com/forum/viewtopic.php?t=136727

http://synovatron.blogspot.com/