horrible engine noise

[huh?do-what?]

i think i found out what the problem is. Haven't had time to correct it yet. Should have figured it out earlier. It seemed like the gain was too high. But I was certain it wasn't. The circuit board has jumpers for gain level. But the board isn't marked. So I went online for the manual and misread the jumper settings. Shoud have caught it a week ago. Had bad noise with previous amp, but gain was jacked up high. Always check the obvious. Dohhh!