[sdiy] VCO that goes SHARP in highest octaves??

Pete Hartman pete.hartman at gmail.com
Thu Jun 9 05:59:31 CEST 2022


Now that you mention transistors, Ben...

Neil:  I'm sure you do probably already know this, but most SMD transistors
have a different pinout than their through hole counterparts.  This has
bitten me a couple of times.

If you haven't ruled this out, perhaps that's related?

Pete




On Wed, Jun 8, 2022 at 10:44 PM Ben Bradley via Synth-diy <
synth-diy at synth-diy.org> wrote:

> Rereading the original, it seems reasonable to assume at least one
> component is different in SMT from thru hole. I'd start replacing SMT
> parts with thru hole and see what happens. I can't quite say why, but
> I'd start with Q5 and Q6, and if no change then Q1-Q2. From there I'd
> do the other active parts. After what you've already tried, this does
> not have an easily identifiable solution.
>
> On Wed, 8 Jun 2022 at 21:15, Neil Harper via Synth-diy
> <synth-diy at synth-diy.org> wrote:
> >
> >
> >
> > On 5/19/22 15:57, Sarah Thompson via Synth-diy wrote:
> > > Chip ceramic capacitors can show changes in capacitance with bias
> > > voltage. If stable capacitance is necessary, then specifying something
> > > fundamentally more stable like a polyester might be sensible, albeit at
> > > the cost of board area.
> >
> > thank you sarah,
> > this is good to know, so I did try swapping the smt cap out with the
> > npo/c0g thru-hole cap that worked as expected and the problem did not
> > change.
> >
> >
> > --
> > /// Neil Harper
> > /// Every Wave is New Until it Breaks
> >
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