I'll try to keep this relatively brief. Basically, I started building my new Axe-FX based guitar rack a couple weeks ago. I decided to pair it up with a solid state Carvin DCM power amp (the new 1540L) so I could get the extra versatility of the power amp sims. Since I first hooked it up, though, I noticed that my rig was making what almost sounds like sort of a crackling hissing noise that is most apparent in high gain patches. It makes the treble pretty uncontrollable, the bass hardly present, and the overall sound pretty crappy. I recorded a quick clip with an Audix OM 2 mic that you can hear here: http://www.soundclick.com/bands/page_songInfo.cfm?bandID=680336&songID=7492589 The setup here is a basswood Ibanez with DiMarzios, into the Axe-FX, into the Carvin, into an Avatar 4x12 with V30s. The patch set up on the Axe-FX is just a Peavey 5150 sim and a gate. The bass is up a bit, the mids are scooped slightly, the treble is actually in the negative range, and the presence is just a hair over 0. It sounds a lot harsher in the room than in that recording. I did make sure that the power amp sims were on and the cab sims were off (not that I had a cab block set up anyway). Of course, I figured I'd find the source of the problem by switching out components until the noise stopped, but it didn't work. I swapped out the Axe-FX with a POD X3. Then I tried two other power amps (one tube and one solid state) in place of the Carvin. Then I switched the Avatar cab out for an old Ibanez cab I had lying around. That noise was always there. I tried different guitars, and I even tried switching out all the cables, using a different power conditioner, and running power through an extension cable from the other side of the house. Nothing. Then I set up the POD, another power amp, and the Ibanez cab into a completely separate rig, and it had the same problem. I'm baffled as hell here. No matter what gear I play through, I have the same problem. Right now, it looks like I either have three broken power amps (one of them being brand new) or two broken cabs (the speakers don't seem blown or otherwise damaged, but I'm no pro with this stuff).