[sdiy] diagnosing polysix output noise (fwd from AH)

[Jimmy Moore]

I can't wait when I figure out where it's coming from so I can figure out
how to patch it in as a reliable effect haha!

Florian and a few others on AH said it sounded like a flaky transistor or
BBD chip.

Modifying the filter cutoff or resonance does NOT change the noise timbre.
There may be a slight relationship between changing the resonance and that
triggering the the noise. But only very slight. Florian called out that
this out:

*Does it depend on the on/off-setting of the effect section? If not then
there are only a few parts that remain as suspects. *

*And just as remark: many people forget, that there is a VCA on the effect
board that is controlled by the resonance setting. So, if the noise depends
on the resonance setting, you can narrow down the source quite well.*

 Curious if that helps localize things any.


I've had the synth droning this morning and it took about 20mins before the
noise emerged. I can get another recording of people want, but it's more of
the same. It appears independent of the effects section being engaged or
not. The resonance setting does not appear to influence its prevalence.


On Thu, Mar 26, 2026, 11:35 PM Adam (synthDIY) <synthdiy at adambaby.com>
wrote:

> Interesting noise!
>
> Sounds to me like the noise is being affected by the filter - would you
> agree? If so, it's not coming from the Effect Board BBD
>
> A
>
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