<div dir="ltr"><div dir="ltr"><br></div><br><div class="gmail_quote gmail_quote_container"><div dir="ltr" class="gmail_attr">On Sat, Mar 28, 2026 at 3:22 PM Richie Burnett <<a href="mailto:rburnett@richieburnett.co.uk">rburnett@richieburnett.co.uk</a>> wrote:<br></div><blockquote class="gmail_quote" style="margin:0px 0px 0px 0.8ex;border-left-width:1px;border-left-style:solid;border-left-color:rgb(204,204,204);padding-left:1ex">I would have said that those strange squeaking sounds were likely beating <br>
between the high-frequency BBD clocks in the chorus section, but you said <br>
it's audible on the audio before if goes into the effects section. The <br>
squeaking sound just sounds similar to the swooshing that you can sometimes <br>
hear at a very low-level in the noise-floor of a normal BBD chorus.<br></blockquote><div><font color="#0000ff"><br></font></div><div><font color="#0000ff">I think your intuition makes sense. My experimentation has shown the noise seems to be added post-BBD chip (IC3 specifically). </font></div><div><br></div><div><br></div><div><br></div><blockquote class="gmail_quote" style="margin:0px 0px 0px 0.8ex;border-left-width:1px;border-left-style:solid;border-left-color:rgb(204,204,204);padding-left:1ex">
Definitely sounds like a loose connection somewhere though from all the <br>
cracking. Are Polysix synths particularly prone to battery leakage damage? <br>
I have a friend who is also currently grappling with some really quite <br>
extensive corrosion issues due to a leaked battery in a Polysix!<br></blockquote><div><br></div><div><font color="#0000ff">very much so, but lots of people have already weighed in here!</font> </div><blockquote class="gmail_quote" style="margin:0px 0px 0px 0.8ex;border-left-width:1px;border-left-style:solid;border-left-color:rgb(204,204,204);padding-left:1ex">
Out of interest have you looked on the positive and negative supply rails in <br>
that area of the circuit? You said there were glitches visible on various <br>
clock signals as well as the audio when you hear the crackles. Just <br>
wondered if there is a bad power supply rail connection somewhere.<br></blockquote><div><br></div><div><font color="#0000ff">I've spot-checked the voltages at different points and things <i>seem</i> 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.</font></div><div><br></div><div> </div><blockquote class="gmail_quote" style="margin:0px 0px 0px 0.8ex;border-left-width:1px;border-left-style:solid;border-left-color:rgb(204,204,204);padding-left:1ex">
-Richie,<br>
<br>
<br>
<br>
-----Original Message----- <br>
From: Jimmy Moore via Synth-diy<br>
Sent: Saturday, March 28, 2026 9:00 PM<br>
To: Adam (synthDIY)<br>
Cc: synth-diy mailing list<br>
Subject: Re: [sdiy] diagnosing polysix output noise (fwd from AH)<br>
<br>
<br>
Great catch, I hadn't listened too critically back to back. Here are two <br>
recordings where you can clearly hear that the noisehas higher frequencies <br>
when the note is playing<br>
<br>
Not playing: <br>
<a href="https://drive.google.com/file/d/1eYx_YXt7WBBX25fwzZ2FOYc6I9fTDbf0/view?usp=drivesdk" rel="noreferrer" target="_blank">https://drive.google.com/file/d/1eYx_YXt7WBBX25fwzZ2FOYc6I9fTDbf0/view?usp=drivesdk</a><br>
<br>
Droning note: <br>
<a href="https://drive.google.com/file/d/1Rp-peon3I2BJ0aEmvOlD7LLR-jI8AMf4/view?usp=drivesdk" rel="noreferrer" target="_blank">https://drive.google.com/file/d/1Rp-peon3I2BJ0aEmvOlD7LLR-jI8AMf4/view?usp=drivesdk</a><br>
<br>
In both cases resonance was at zero and cutoff was about 25%<br>
<br>
I don't know the signal path or how it corresponds to stages of the <br>
schematic, maybe someone can help out here. But would this imply that the <br>
noise source could be between the filter and envelope generator?<br>
<br>
<br>
<br>
<br>
<br>
<br>
<br>
<br>
On Fri, Mar 27, 2026, 3:34 PM Adam (synthDIY) <<a href="mailto:synthdiy@adambaby.com" target="_blank">synthdiy@adambaby.com</a>> wrote:<br>
<br>
<br>
<br>
<br>
<br>
On 28 Mar 2026, at 00:50, Jimmy Moore <<a href="mailto:jamoore84@gmail.com" target="_blank">jamoore84@gmail.com</a>> wrote:<br>
Modifying the filter cutoff or resonance does NOT change the noise timbre. <br>
There may be a slight relationship between changing the resonance and that <br>
triggering the the noise. But only very slight.<br>
<br>
<br>
<br>
But you'll agree that in your example recording, the noise has more high <br>
frequency content when the note is playing, than later when the note dies <br>
away?<br>
If not affected by the filter directly, then there may be some relationship <br>
with the note envelope<br>
<br>
<br>
<br>
<br>
On Thu, Mar 26, 2026, 11:35 PM Adam (synthDIY) <<a href="mailto:synthdiy@adambaby.com" target="_blank">synthdiy@adambaby.com</a>> <br>
wrote:<br>
Interesting noise!<br>
<br>
Sounds to me like the noise is being affected by the filter - would you <br>
agree? If so, it's not coming from the Effect Board BBD<br>
<br>
A<br>
<br>
<br>
<br>
<br>
<br>
<br>
<br>
<br>
<br>
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