On Sat, Mar 28, 2026 at 3:22 PM Richie Burnett <rburnett@richieburnett.co.uk> wrote:
I would have said that those strange squeaking sounds were likely beating
between the high-frequency BBD clocks in the chorus section, but you said
it's audible on the audio before if goes into the effects section. The
squeaking sound just sounds similar to the swooshing that you can sometimes
hear at a very low-level in the noise-floor of a normal BBD chorus.
I think your intuition makes sense. My experimentation has shown the noise seems to be added post-BBD chip (IC3 specifically).
Definitely sounds like a loose connection somewhere though from all the
cracking. Are Polysix synths particularly prone to battery leakage damage?
I have a friend who is also currently grappling with some really quite
extensive corrosion issues due to a leaked battery in a Polysix!
very much so, but lots of people have already weighed in here!
Out of interest have you looked on the positive and negative supply rails in
that area of the circuit? You said there were glitches visible on various
clock signals as well as the audio when you hear the crackles. Just
wondered if there is a bad power supply rail connection somewhere.
I've spot-checked the voltages at different points and things seem ok. not sure if anyone has a working specimen to provide spot measurements but I can report back with some specific voltages if that'd be helpful.
-Richie,
-----Original Message-----
From: Jimmy Moore via Synth-diy
Sent: Saturday, March 28, 2026 9:00 PM
To: Adam (synthDIY)
Cc: synth-diy mailing list
Subject: Re: [sdiy] diagnosing polysix output noise (fwd from AH)
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@adambaby.com> wrote:
On 28 Mar 2026, at 00:50, Jimmy Moore <jamoore84@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@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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