I've been noticing some odd issues when playing on my Mesa Rectoverb....AGAIN. For the past few months or so, I feel like I haven't been getting the same full distortion as I used to get through my Schecter Hellraiser; for instance, the palm mutes sound sterile, for lack of a better term. At first I thought it may have been the guitar, since I noticed it after I put on new strings, but I get the same result with my Fender HSS, though to a lesser extent, and I even changed the battery on the Schecter. There's also a persistent hum on the distorted channel when my guitar is plugged in, but I'm not playing. And finally, my cleans are behaving strangely, in that when the reverb is on I'm getting a slight crackle when I strike a chord.
I should also note, I had a friend mod the amp for me, but I'm not entirely sure what he did. Power tubes are Mesa-brand, and I replaced them about nine months ago. So what could be the issue?
Quote by Jackal58
I eat dead meat all the time. You don't have to chase it around your plate and it doesn't try to peck your eyes out.

It Happens.

My Gear:

-Custom Fender MIM Black Strat
-Mesa/Boogie Rect-O-Verb
-Schecter C-1 Hellraiser
Maybe one of your preamp tubes is microphonic? I have limited tube knowledge but from what you are saying and what I understand this might be the case.