[sdiy] modular synth "standards"

[Tony Allgood]

DT>For a 10V p-p output, the audio sawtooth wave would then go from -5V
to +5V volts while the LFO modulation sawtooth would go from 0V to +10V.

I would tend to disagree. And I say tend, because both options have
their place. And Harry did say there were two schools of thought here...

I would hate to think that a triangle or sine LFO would vary between 0
and +10V. For me the nicest vibrato is bipolar. But for a square wave I
would make it unipolar for trills. For saw, a choice of either is
probably quite nice. But I also find that I would like a 1V p-p LFO
signal for driving VCO pitch. I find that even with a log pot, I can't
get the precision in vibrato when using the straight 10V p-p into a
attenuated '1V/oct' input. Using an additional secondary 10:1 divider
gives me the control I need. Didn't the Roland 100M modules have a 10:1
switch on some of the CV inputs? Good idea that.

One can always add DC offsets to the input of the controlled module.
Although most VCAs don't have a DC-bias input on the controlled side.
Good idea to add one though.

By making all signals the same size you will get the same SNR and
headroom from all signals. For example: You make your VCAs good enough
for a 10V p-p signal, more like 20V p-p, so you can use it for CVs and
then you bung a 0dBV input when controlling audio. Effective CV
breakthrough and noise will be higher. Running everything very hot will
keep those noise levels as low as possible... unless you have separate
VCAs for CV and audio.

The difference in standard audio and modular levels is not really that
bad. Most mixers will allow large signal levels into them without too
much problem. Aux outputs easily produce the required 10V p-p needed.
Besides a simple resistitive divider can be used to drop signals down
easily. I think it was Harry who said he had the pad inside the jack
plug.

However, it is a good idea to have a pre-amp and output amp module in
any modular.

Just my thoughts.

Regards,

Tony Allgood  Penrith, Cumbria, England

Oakley Modular Synth and TB3030:
www.techrepairs.freeserve.co.uk/projects.htm
My music: www.mp3.com/taklamakan