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Single Rectifier Problem

Posted: Wed Oct 03, 2018 6:14 am
by deadtotheworld
Hi
I traded my evh 5150 iii 50w for a second hand Single Rec and had it checked over by an amp tech and all seemed fine.

However at rehearsal I put an mxr carbon copy in the fx loop and there was a high pitch squeal. The squeal sounded almost digital and not loud in volume but loud enough for the band guys to say 'what the hell is that?'
I took the pedal out of the fx loop and it stopped. I continued rehearsing with an mxr evh 5150 overdrive in front of the amp using the clean channel.
Later on i decided to use the gain channel on the amp so plugged in the 5 pin cable to use the amp foot switch and the squeal started again.
I noticed it especially when I was still on the gain channel but turned the volume all the way down on my guitar. My decimator noise gate doesn't stop it either.

Ive tried different guitar leads, different guitars, different plug sockets, different rooms in the rehearsal place. It just seemed the noise appears when there is something plugged in the back of the amp be it 5 pin or fx loop.

EDIT: Just to add, the sound seems like its coming from the head rather than through the speakers.

Any ideas?

Any help or advice would be much appreciated. Thank you in advance.

Re: Single Rectifier Problem

Posted: Wed Oct 03, 2018 8:24 am
by deeman
Is the FX level knob on the back of the amp turned all the way up? If so, try rolling it back a little bit.

Re: Single Rectifier Problem

Posted: Wed Oct 03, 2018 8:55 am
by deadtotheworld
Hi
The fx loop knob makes no difference to the noise, I tried turning it all the way up and all the way down and it didn't alter the noise. It was just strange that the sound disappeared when i unplugged from the fx loop, but started again when I hooked up the 5 pin foot switch????

EDIT: Just to add, the sound seems like its coming from the head rather than through the speakers.

Re: Single Rectifier Problem

Posted: Fri Oct 19, 2018 12:45 am
by afu
Does it happen all the time now? Have you tried changing any tubes? Does it make a difference if you plug in the foot switch while the amp is off and then turn it back on.

If it doesn't squeal all the time, you can try replacing the loop's tube. I believe that is #4 from the left when you look into it.

If part of the switching system went bad, it can cause problems. If the sound goes away when the foot switch is used to deactivate the loop, and you already tried replacing tube 4, take it to a tech. If none of it works, take it to a tech

Re: Single Rectifier Problem

Posted: Wed Nov 07, 2018 12:14 pm
by deadtotheworld
I bought a full set of new tubes from Watford valves. Replaced them all and the problem has gone!