[sdiy] ASM-1 VCO section update

[Tony Allgood]

>Now, you where discussing the use of diffrent transistors, but using
sawtooth does all the trick?

I was originally talking about using another FET to discharge to cap.
This would be in parallel with the ordinary one, but controlled by the
sync pulse only. The rack mounted Dual Moog VCO does this. I haven't
tried it. I think one of Tom G's VCOs did something similar, maybe the
Prodigy too. This is real hard sync.

However, I have been happy with using the sawtooth from mine. My VCO
gives a saw down, so you get the nice positive blip from the
differentiator on the sync circuit. Saw up wouldn't work though. The
advantage of this method is that you can get soft sync quite easily.
Although I don't tend to use it that much, its quite good to use it when
locking to harmonics for organ type sounds.

And Tom (May), your circuit looks handy too for generating hard sync.
You may want to add a little hysteresis (positive feedback) around that
comparator at the front. That'll make it switch a lot cleaner and faster
too. I would use 10K input resistor & 3M3 around the loop or somesuch.

Regards,

Tony Allgood  Penrith, Cumbria, England

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