Another thought - if your op-amp input is hitting a power rail, it is
possible the op-amp is going into phase-reversal/lockup because its common
mode range has been exceeded.
Cheers,
Ken
Ken Stone sasami@... or sasami@...
Modular Synth PCBs for sale <http://www.blaze.net.au/~sasami/synth/>
Australian Miniature Horses & Ponies <http://www.blaze.net.au/~sasami/>
possible the op-amp is going into phase-reversal/lockup because its common
mode range has been exceeded.
Cheers,
Ken
>_______________________________________________________________________
>> The 200k is providing an offset while the 600k is providing the
>gain -
>> supposedly. These aren't the values I specify.
>>
>
>That's precisely what I'm going to look at tonight. With a solid 2
>1/2 volt saw from the core, I don't need a gain of 6. Also, as I'm
>seeing the positive rail at the output of an inverting amp, that must
>mean the offset resistor is too low. Perhaps these two resistors
>were to be the other way around!
>
>By the way, Ken, I've been playing with the core of this VCO. When I
>get this sorted out, these VCO's will see some heavy usage! A very
>nice design, in my opinion. Easy to set up, lot's of modulation
>possibilities, the sub oscillator and the VC saw/sine shaper which is
>really the icing on the cake.
>
>To everyone on the list- this is really MY error, not the pcb or the
>design. And it may seem like I've been working on this for a long
>time, but that's because I don't really get enough time to work on
>it - a few minutes here and there. Thanks for your suggestions and
>ideas! Buy lots of Ken's VCO's, too.
>
>Chub
>
>
>
>
>
>See the following URLS for the CGS Modular Synth home page:
>Main: http://www.cgs.synth.net/
>Secondary: http://otherunicorn.0catch.com/synth/
>Yahoo! Groups Links
>
>
>
>
>
>
>
Ken Stone sasami@... or sasami@...
Modular Synth PCBs for sale <http://www.blaze.net.au/~sasami/synth/>
Australian Miniature Horses & Ponies <http://www.blaze.net.au/~sasami/>