Hey guys! First post here. So I've always associated solid state amps cranked on the clean channel with this horrible raspy kind of overdrive, but... well I'm a guitar teacher, and I bought a cheap old guitar/bass/organ montgomery wards amp for kids to use at the studio, and cranked it sounds amazing

What gives? What's going on in the circuit that makes one cranked SS amp sound awful and another sound very musical?

Thanks!