vco8b ( Pick up that Axxe Eugene! )

[tomg]

Here is the Axxe VCO revised. Once I removed the loading
from the schmitt trigger by putting resistors between the fet
buffer and trigger/outputs and took the output from the fet
instead of the trigger diff, I was able remove the hi-comp 
resistors. There doesn't seem to be any temp-related drift
garbage associated with the trigger-pair.  Discrete trannys
seem to work well. Scaling is easy and sounds very good.

I added the sync scheme from the 2600 vcos and stuffed the
expo-converter and schmitt trigger pair in a CA3096. I know
the pnps in the 3096 are crap. I guess there is always a place 
for even the most crap components because it does stabilize
this vco design. 

Here is something interesting...using discrete trannys...holding 
the npn-expo the freq goes up, holding the pnp the freq goes
down, holding them both cancels. Wrapping them up in heat-shrink 
with thermal compound and a temco it becomes very stable, putting 
them in the 3096 it becomes very very stable. Putting them in the 
3096 with a temco it becomes bed rock.

After working on it last night. I set the freq to 830Hz and turned it
off. After sitting on the bench in the garage overnight I walked in
today, turned it on and the freq was 831Hz. It went to 830Hz in
about a minute.

I might do a dual-vco w/ringmod for CAM2 if you want 'em.
I would be pleased if somebody could build one of these and 
confirm this. 
 
http://www.xavax.com/efm/synth/cbook/pics/vco8b.gif

Thanks to everyone who sent me stuff and/or links. You are the best!

-tg