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500Hz noise / whine from Doepfer A100 case w/ PSU3 - help!
MUFF WIGGLER Forum Index -> Modular Synth General Discussion  
Author 500Hz noise / whine from Doepfer A100 case w/ PSU3 - help!
prae
Woke up this morning to find a horrible whine coming from my Doepfer case. Hadn't made any changes prior to turning it on that day, aside from plugging in my Rytm to the same mains socket (obviously disconnected to check that out)

Ripped the modules out and replaced one by one, thought I'd solved the issue as the DIY QPLO appeared to be causing the issue. Continued to test one by one - all seemed fine.

Then I got the problem again when patching between rails - so something from the second rail to the third introduced this noise.

I've measured it and it's around 500Hz and the harmonics of.

I'm using a pittsburgh I/O as my final module. It's going in to a Mackie mixer but I've also plugged it directly into my interface to bugcheck also.

What gives? Deeply confused here. To me it screams of a shared grounding issue but not sure how to diagnose / solve.
Rex Coil 7
prae wrote:
... Then I got the problem again when patching between rails - so something from the second rail to the third introduced this noise...
Just to clear up my confusion, when you say "rails" are you meaning rows of modules ("rails" = "rows")? Or are you saying something to do with the power rails?

Jus' checkin'.

cool
Rex Coil 7
Can you also provide more information please?

Power supply brand/model? (SCRATCH THAT .. "PSU3" used, got it!).

Are bus boards being used (if so, brand/model is applicable)?

Age of PSU and distribution system?

Are any digital modules that use capacitance/contact points being used (EG; Make Noise Rene)?

cool
unrecordings
I'm assuming rack rails - and that the noise is not physical psu noise:

You might need to isolate the module - like you've already tried, but in a different way. So either row 2 or row 3 is the issue - what happens when row 2 or 3 are patched into row 1 ?

Maybe there's a super noisy module (as Rex points out) that needs to have its power cable moved
ersatzplanet
Also be aware that the +5v line on the PSU3 supplies is the un-filtered switcher line. The +/-12v lines have linear regulators on them. If you have a module that can optionally use the +12 or the +5 (usually with an internal jumper), try switching options.
prae
video for clarity here
https://youtu.be/Yrg8S2UoXHE
prae
Rex Coil 7 wrote:
Can you also provide more information please?

Power supply brand/model? (SCRATCH THAT .. "PSU3" used, got it!).

Are bus boards being used (if so, brand/model is applicable)?

Age of PSU and distribution system?

Are any digital modules that use capacitance/contact points being used (EG; Make Noise Rene)?

cool


yeah it's this http://www.doepfer.de/a100p_e.htm#A100P9
with the PSU3, about 3/4 years old. busboards are the doepfer included ones.

no capacitive modules used.

have swapped some modules around and seems like different modues / placement leads to different results... but not consistently either...
ersatzplanet
I will venture to point the finger at any digital module on that row. Pull the modules (from the video only showing part of that row, I would start with the one with the display). Usually if the problem happens in one row only in a cabinet that shares the supply wit more than one row, faulty wiring to that row, or modules on that row are typically the culprit.
prae
alright, put some of the modules in a 2x HEK with uZeus... things are fine...

so it's either the modules that aren't being used

or

the doepfer case

further explorations next week...
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