Low end distortion on the clean channel

[mforker]

hey folks,
I have a Mark IIb w/ GEQ and reverb that's been acting a bit strange recently. When I'm on the rhythm channel theres a subtle distortion on the lower notes almost like amp breakup, the only catch being that until this week, I've never heard the clean channel break up even a little - even with the volume dimed and the master low. Any thoughts? I've also been having an issue with the reverb (it's much more apparent on the clean channel than the lead) if anyone thinks that that's relevant.
Thanks!
Matt

 

[jediguitarist]

Don't know if this will help, but I had the same issue with my Quad preamp after a couple years. I'm sure there are some common fixes to try.

Same as you, I noticed a slight buzz/distortion on only the clean channel. I was living with it for a couple years since I never ran a pure clean channel. After getting a Mark IV combo, I put the Quad into storage for almost 5 years. When I recently took it back out to use, the issue was still there.

I took it to an authorized Mesa repair center and was able to recreate the at the shop. The tech heard the distortion and an said he would open it up and see if anything came up. After a week, I got the call saying the amp was done. The tech said he did a thorough cleaning of the pots, jacks and reverb tank connectors and didn't replace anything. Powered it up at the shop and the distortion was gone. Brought it home and hooked it up to my power amp and it worked perfect since. The tech only charged me the $20 bench fee and an hour of labor. I think it was $75 total.

Maybe all your amp needs is a good cleaning with some contact cleaner. At least it's a place to start.