need help making a keyboard (and my vco is stupid.. or maybe I'm stupid)

[Andrew Schrock]

On Wed, 27 Jan 1999, Reverend bluE wrote:
> on a different note (or lack there-of) I finished my second VCO 
> (Maxx2 VCO-2D except I swapped the 2N3904 tranny pair for a MAT-02)
> and it wouldn't work at first, then I realized that I had the +/- power lines
> reversed, so I switched them and it worked, but barely.  On square output, the
> fine tune barely worked, and I could only get sound with the PW pretty much
> centered.  and the turning "sweep" for the PW pot was very limited.  I then
> noticed that I had the PW pot and the fine tune pot switched (10k and 100k),
> and that I had  my jacks hooked up backwards (ground to tip) so I swapped
> those and now it won't work at all.  

No, I think this is normal. My VCO-2's exhibit this same type of
pulsewidth weirdness... very small range of initial PW tuning, and then
harder to tune again once you add PWM in. I'm going to play with
resistance values (that's really all that's the problem, the PWM sounds
great otherwise). I'll post results later, I should have done this a month
ago.. grumble.. no time. 

I put 10-turn bournes pots for my pitch tuning, but just cuz I happened to
find them laying around. No problems with 'em, the pitch is fine. The
VCO's scale fine for me as well, but you didn't mention that. 

Try going back and rechecking your work. You won't get anything to work
past 1am ;) I've had many a project saved cuz I gave up and went back the
next day. 

Andrew

-| Andrew Schrock | aschrock at cs.brandeis.edu |-