[sdiy] Programmable ICs / Scaling

[john mahoney]

In most cases, a programmable device would be overkill. If you insist,
though, it's a no-brainer: the PSIM-1.

The PSIM-1 has 4 CV inputs, 4 CV outputs, and a Hitachi microprocessor in
the middle. You could write your own conversion program in BASIC, but there
are already 2 quantizing programs in the Yahoo group files area. There is a
4-channel chromatic quantizer and a "1 ch Quantizer with ch2 in cv
controlled quantization resolution." Just modify one of them and you're
done. More info is at http://www.synthmodules.com/. (I am not affiliated
with synthmodules, I merely own a PSIM.)

Anyway, to scale a control voltage linearly, I believe that all you need are
adjustable attenuation, gain, and offset. In other words, a couple of pots
and an op amp.

However... Some old gear (old Korg and PAiA, for example) uses linear VCOs
(V/Hz) instead of exponential VCOs (V/octave), and that's a bigger problem.
There are a few ways to handle that, one of them being a PSIM-1.
--
john


P.S. Everybody, *please* forgive the enthusiasm of the small group of PSIM
users. We're excited! This is the Swiss Army Knife of modules. That's been
said of other modules, but it's really true of this one. Nothing else can
assume so many personalities, and nothing else has such an easily
programmable brain. Okay, I'll stop. For now...


----- Original Message ----- 
From: "nN AAt e e" <timexheater at comcast.net>
To: <synth-diy at dropmix.xs4all.nl>
Sent: Thursday, March 04, 2004 6:32 PM
Subject: [sdiy] Programmable ICs / Scaling


> i just got to wondering how one would go about say... taking something
like
> a performance synth that may not be 1v/oct and doing the math to figure
out
> what the scale is, then make something to convert it to 1v/oct...
>
> ...while mostly using programmable ICs as to make it [slightly] easier to
> deal with math problems.
>
> i know this isnt very hard to convert old korg/paia standards to roland
> using analog based converters, but what would be good ICs to check out
that
> should be able to handle the voltage ranges of a synth? it doesn't seem
like
> it would be too difficult using something like PICs or Stamps, but i
havent
> really worked with either of them before.
>
> has anyone here made any custom scaling devices?
>
> this would probably be only used for cv output [nonstandard-> 1v/oct], but
> 1v/oct inputs would be pretty cool later on too.
>
> - nate
>
>