fdesalvo said:I just don't get how ppl can honestly say their MKIV can't get super tight, saturated, or lacks low end
+1
If I had a Mark IV with any of those symptoms I'd do the following:
1) Preamp tube swamp and if that didn't work,
2) Poweramp tube swap and if that didn't work,
3) package it up and send it to Petaluma for a checkup.