[sdiy] ASM VCO with 12V supply?

[Magnus Danielson]

From: Fortner Florian <florian.fortner at fh-joanneum.at>
Subject: [sdiy] ASM VCO with 12V supply?
Date: Tue, 19 Mar 2002 22:00:48 +0100

> Hello List,

Hi Florian,

> The Littleman Synthesizer design uses a V/Hz VCO supplied with +-12V, would
> this VCO be replacable with the ASM VCO (working with +-15V) which provides
> V/oct CV? Or do one need to recalculate the whole circuit?

I do not beleive that there is any major problems to solve in order to
run it as +/- 12V. If you want to ensure properties you need to adjust
the resistor giving exponential transistor-pair reference current,
just recale by 12/15. Also, the LM311 comparators reference voltage
then needs adjustment, so that the voltage divider of 20k/10k gives
you +5V. This is just from the top of my head. I don't recall if the
waveshapers need attention, but it is equalently easilly fixed.

So, if you need to recalculate things, there are really only a few
components involved anyway. I know that some people have done it, so
it is not at all unfeasable.

> The other
> possibility would be an exponential converter but then the part count is
> going to be VERY high for a single VCO.
> Any recommendations?

It is easy enougth to build a expo-converter and you should be able to
hook it in.

Cheers,
Magnus