I have a Peavey XXL (solid state) amp on the bench. Sounds great until you flip it to the Ultra channel then its squeal mania. It happens across all volume, gain, and eq levels and with different guitars, cables , etc. The issue is in the amp, in the Ultra channel only. The squeal goes away when your actually playing but as soon as you stop its there piercing your ears. Where should I start? I plan on getting it hooked up to my oscope today to see if I can see it.