[diy] moog VCOs

[tomg]

Hi Tony..Did you know the original Moog Modular VCOs used 
unijunction transistors? I didn't until recently. I think I'm going to
try one of those sometime...

> What the heck is a E112 FET? Is it the same as a J112? I have tried it
> with a BF244 and a 2N3219. The former produces a higher value of saw
> peak. The latter doesn't turn-on hard enough to charge the cap up to the
> +5V reference. I guess I need a FET with a lower channel resistance.

I bought a few J112s to try, just haven't gotten to it. I have a pair of
E112 
to compair them to. I'll let you know how it goes. It would be great if it
works J112s are $0.79. A 2N4391 or 4392 should work but they cost
3 times as much.

> Are there any differences in using the expo transistors the other way
> round? That is; in most of my previous expos, I sink the VCO/VCFs
> current in the transistor that has the control voltage applied. This is
> the same as the Formant and the ASM-1 I think. But the minimoog VCO uses
> the second one, with the op-amp's feedback going to the first. At first
> glance, I cannot see any advantage in doing this, but am I missing
> something?

I don't think so. I've tried it both ways...no big difference??? AFAI could

see. You might want to use Terry's front end for the ASM-1's VCOs
instead though... 

-tg