AW: volt.contr.ideas

[Haible Juergen]

Very good thoughts!
Especially the string vibrato being in upper direction only
 - never thought about that, but it sounds reasonable!
As for standards: You showed the main problem yourself:

> Generally I don't want to make a sharp decision between audio or subaudio
> devices or voltages since it is the great advantage of a modular system
> that everything can communicate with everything.

But you recommend 10V levels for modulation and 2V levels for
audio. (And you have some good reasons for this !)

It really *is* a dilemma. For audio signals, sometimes a level
in the range of 50 Millivolts (!) has advantages. If you look
into the Minimoog VCA, there are actually two VCAs in series
(one for envelope, one for pedal). Why amlify the signal up
(with slew-rate and all the other side effects of opams) and
then divide it down again for the next differential pair?
The Minimoog methode is much more elegant, and surely
more pleasant to the ear.
Or the same thing on filters: Why clamp each ota into a
10V/20mV divider / feedback loop (most 3080-based
filters I have seen, and the 3320 is not much better ...)
The Moog filter and SSM2044 are far more elegant with their
direct coupling. (2040 is in-between, but a case of its own).

Ok, this were some general thoughts, which I try to make use
of in my PolySynth. But it won't help us much for a Modular,
where you want to have an interface between all and everything.
IMO, there are two possible solutions: Either go for a standard,
and use the same level for Modulation and Audio (and even for
Gate and Trigger ...) - That's what I did on JH-3.
Or - and that would really be a good alternative! - don't care too
much for standards at all and make inputs variable with
logarithmic pots over a wide range. So instead of your usual
100k/220R divider for an OTA, go 10k/220R and spend a logarithmic
pot at the input. And so on.
In retrospect, I think I did rely a bit too much on my standards
of my JH-3 Modular. All and everything is 5V standard. Now I
use the Modular as a testbench for my evolving PolySynth boards,
and these need 10V envelopes. I hate to admit it, but I have not
included a simple x2 DC amplifier in my System. Ok, I can help
myself by overdriving a VCA and things like that, but well, now
I learn standards are not all there is.

Just a few thoughts.

JH.