Champ Reverb Amp Whining/Squishing Noise

molomo74

TDPRI Member
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Aug 12, 2021
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27
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Germany
Hello,

i recently built a SE Princeton aka Champ Reverb Amp. It worked finde for a while but since a few weeks i have a strange whining/squishing noise (sound sample attached) when the amp is at idle. None of the controls affects the (quite low volume) noise and the amp functions normally apart from that noise. I tried pulling the preamp tubes one after another and after i pulled all three the noise is gone. When i pulled V3 and the noise stopped, i replaced V3 with V1 (so a different tube) and the noise was present again. So i doubt it is a preamp tube related problem.I tried chopsticking the amp around V3 and even rearranged some wires without any success.
As i said the amp is quite new and so are the components (Filter Caps (F&T) etc.).

I also atteched the schematic and a sound sample.

Any help i highly appreciated.
 

Attachments

  • Champ Reverb Noise.zip
    193.4 KB · Views: 58
  • SCHEMATIC CHAMP REVERB_compressed.pdf
    601.9 KB · Views: 17

King Fan

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Jan 1, 2013
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Hmm, I see you're not getting too many suggestions. If it helps, here's your schematic so folks can more easily see it:

SCHEMATIC CHAMP REVERB_compressed copy.jpg


I was able to download and play your sound clip -- it might help readers if anyone can tell us how to include it as a click-to-play file.

Other things that often help in 'problem' threads are clear, well-lit pics of the build, a layout diagram if you have one, and a complete voltage table.
 

rdjones

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Nov 6, 2010
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772
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Music City, TN
You've copied the 'rectifier pin 2 mistake' although I'm not aware of it having caused this type of noise.
Still, it's best practice to pull B+ from pin 8.

I'd disconnect the reverb send and return to see if the noise is still there/same.
Try shorting an input jack as well.
Is the chassis enclosed and shielded ?
 
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