[sdiy] SBM VCO CV interference

[tomg@efm]

It's truly wierd...I've just been going over the sbm on my bench
and see nothing like what you are describing. Is your TV on?

Tom



> On my EFM SBM, I am getting a strange problem.
>
> On my input CV line which consists of 1 input and 3 tune pots (freq, fine
> and init freq trimmer), I am getting an odd narrow pulse-wave signal on my
> scope - it changes frequency along with the signal CV.
>
> This causes weird harmonics in the output signals (sine, tri, saw, pul)
and
> is most noticeable at higher frequencies.
>
> The pulse wave seems to actually be two signals: a full cycle narrow
pulse,
> and a half-cycle (positive only) at 90 degrees offset. How bizarre!
>
> I checked all my grounds and traced the problem back from the opamps, but
> have no where else to check the signal - it's the start of the circuit! -
I
> am using no input on the cv (although have tried using a cv input which
does
> not help the problem).
>
>
> Anyone else run into a similar problem on their SBM or analog synths?
>
>
>
> Rob
>