Sort of off-topic:
Interesting thread, since I've been hard-pressed to get some comparisons between the Mark IV, which I'm considering getting, and the DC-3, which I just bought used, and my 60-Watt 6505, that I've had for a while, but totally intend to keep.
From what the TS has said, it sounds like something's wrong with his amp. I doubt it has anything to do with his playing, his speakers, his guitar, or his pick-ups, because the words "fizz" and "ice pick" are the LAST words that come to mind when I think of Mesa amps. With all the heat and current running through these amps, after over ten years, something's bound to go out of spec.
Also, if he bought it used, there may be an unknown, homebrewed mod that he's simply unaware of. You know, maybe someone in the past was trying to "fix" the Mark IV's dark sonic character somehow. Also, I never really heard anyone complain about JJ preamp tubes. Is that a Mark IV thing? I happened to put TungSol 12AX7s in my DC-3, and JJ EL84s in the power stage. Sounds pretty good.
Now, on to my brief off-topic thing: I've read some descriptive comments here about the Mark IV. Comments I've been trying to solicit more explicitly in my own, on-topic threads. More specifically, for anyone who's played both, how does the Mark IV's lead channel compare with the DC-3's lead channel? The DC-3 actually has quite a bit of gain. It's just a very different-sounding gain from my 6505, which utterly pwns the DC amp's lead channel at low volumes. Turn the DC-3 up, and it starts to have that signature Mesa gritty-growl. Is that sound that much different compared with the lead channel on the Mark IV, and if so, HOW is it different?