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

[Jimmy Moore]

Great catch, I hadn't listened too critically back to back. Here are two
recordings where you can clearly hear that the noisehas higher frequencies
when the note is playing

Not playing:
https://drive.google.com/file/d/1eYx_YXt7WBBX25fwzZ2FOYc6I9fTDbf0/view?usp=drivesdk

Droning note:
https://drive.google.com/file/d/1Rp-peon3I2BJ0aEmvOlD7LLR-jI8AMf4/view?usp=drivesdk

In both cases resonance was at zero and cutoff was about 25%

I don't know the signal path or how it corresponds to stages of the
schematic, maybe someone can help out here. But would this imply that the
noise source could be between the filter and envelope generator?







On Fri, Mar 27, 2026, 3:34 PM Adam (synthDIY) <synthdiy at adambaby.com> wrote:

>
>
> On 28 Mar 2026, at 00:50, Jimmy Moore <jamoore84 at gmail.com> wrote:
> 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.
>
>
>
> But you'll agree that in your example recording, the noise has more high
> frequency content when the note is playing, than later when the note dies
> away?
> If not affected by the filter directly, then there may be some
> relationship with the note envelope
>
>
> 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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