[sdiy] Basic Synth Patch? VCO-VCF-VCA

[john mahoney]

Mike,
I'm no Synth God, but I'll take a stab at it. :-)

I've had the same thought: Without a VCA in front of the VCF, you don't have
voltage control of the filter's input level, so you can't overdrive the
filter under VC in that way, which could be a useful technique. Actually,
you don't need an AM control on each VCO, all you need is one VCA after the
VCO mixer. (You need multiple VCAs to do VC mixing of the VCOs, but that's
another story.)

On the other hand, if you are *almost* overdriving the VCF (usign a good
amount of resonance), it will overload when the center frequency hits a
"sweet spot" where the input signal is strong, e.g. near the fundamental
frequency. This is voltage controlled overdrive of a sort, but not through
simple amplitude control.

You can get a great "growl" effect when the filter sweeps through a sweet
spot and goes into overdrive.
--
john


----- Original Message ----- 
From: Michael Boracci

Dear Synth Gods,
I need to understand the basic synth patch of VCO-VCF-VCA. It seems to me
that one more VCA would be needed between the VCO and VCF. There has been
mention, several times on this list about overdriving the Moog filter. How
would this be done with VC, if a VCA is not used between the oscillator and
filter?

In addition to the basic amplitude control function I would think that since
there is an FM input on most VCO's, there should be AM as well right?
[snip]