High-pitched squeal from amp - with gain and volume

It probably has nothing to do with it, but did the bias adjustment control between V3 and V4 get bumped or moved?
 
While driving, a thought occurred to me. Another thing I changed was removing the FX cables. The only thing active in the FX loop was the "Kleon-ulator" buffer. As I understand it, buffers can cause such issues. I will test this later with both speakers. Does this make sense?
 
DonP said:
OK. One really useful test. Can you plug your guitar into the effects loop return socket? I know it's the wrong place, but it effectively disconnects the whole front end, letting us eliminate or implicate that.
Click to expand...

RVA said:
I will do that, into Send I presume. I am not in front of it at the moment (at work unfortunately)
Click to expand...

Just to be safe, and clear, I didn’t see anyone correct this...after Ray’s quote above.

Ray, to bypass the preamp tubes, you plug in to the “return” power amp input- marked in red here:
ECEBB6EA-E7E2-48EF-A7E9-A386AEFFBDA8.jpeg

Again, just being sure to be clear.
 
Indeed.
Especially since he was reading all of that while not in front of the amp in question.
There have been some good, sensible, suggestions for troubleshooting so far.
I hope a simple solution presents itself to Ray shortly.
 
Ray said,
"I have a loud, whistling-type, constant feedback when on the clean channel and using high gain pedals
- when there is medium to high gain
- with high volume for this 20W amp
- that is NOT reduced by turning the guitar volume all the way down
- that is NOT reduced by walking approx 25 feet away
- that is NOT reduced by touching the strings
- that DOES breifly go away when actually attacking the strings while playing
- that DOES go away with amp volume reduction (either master or channel)
- it DOES reduce when I turn off delay and reverb."

I know this is completely out of left field but could
it be a power problem in the pedal chain?
Are you using isolated power supplies for the pedals
involved or is there a daisy chain in there?
 
RVA said:
What about my buffer theory?
Click to expand...
Yes, I’m curious about that one too. I’ve never experienced the problem that you’ve presented.
I have seen microphonic tubes in action. They can present themselves under similar circumstances to your outline of events. I suppose that the buffer could be a contributing factor. Heck, it could be the cause, for all I know.
 
Tony M. said:
Ray said,
"I have a loud, whistling-type, constant feedback when on the clean channel and using high gain pedals
- when there is medium to high gain
- with high volume for this 20W amp
- that is NOT reduced by turning the guitar volume all the way down
- that is NOT reduced by walking approx 25 feet away
- that is NOT reduced by touching the strings
- that DOES breifly go away when actually attacking the strings while playing
- that DOES go away with amp volume reduction (either master or channel)
- it DOES reduce when I turn off delay and reverb."

I know this is completely out of left field but could
it be a power problem in the pedal chain?
Are you using isolated power supplies for the pedals
involved or is there a daisy chain in there?
Click to expand...
Yes, all Furman
 
Lets look at the real deal I know it's a 100 watt but Nik made a 20 watt version
1, V-1 use a good GE 7025 tube next chopstick the coupling capacitors they can be micro-phonic
2, the effects loop is connected from the phase inverter to the master volume

124 low plate classic rev1.jpg

100 watt low plate classic 2008 001.JPG
 
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The result is the same with the buffer in the effects loop or not, or in the effects loop engaged or not.
 
67plexi said:
Lets look at the real deal I know it's a 100 watt but Nik made a 20 watt version
1, V-1 use a good GE 7025 tube next chopstick the coupling capacitors they can be micro-phonic
2, the effects loop is connected from the phase inverter to the master volume

View attachment 25063

View attachment 25064
Click to expand...
Thank you. Which ones are the coupling capacitors? Does the behavior stike you as a problem with the amp, or just how it handles high gain pedals?
 
Your amp is concerted a low plate 100k 1.5k 100k 1.5k low gain tap on the orange capacitors with the amp on don't get shocked.
My guess is your 12AX7 first tube close to the input. take your ohm meter and check the orange drop capacitors get a ohm reading then flip the leads
180 degrees and should read open or zero do this test power off it could be an oscillation issue. If you get a reading both sides you have a leaking capacitor.

Next would be voltage chart the amp

Voltage Chart.JPG
 
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