my distortion channel went.

[gutsofgold]

i know this is a pedal forum but i'm dealing with a solid state bass amp and figured the workings couldn't be too far away from a pedal. it's a sunn concert bass and the distortion channel on it is spitting out a crackly sound, something the amp never did. the distortion on these amps is a smooth overdrive emulation.

would anyone know what could be the culprit here? or how i could start troubleshooting it? thanks!

here is the schematic: http://www.freeinfosociety.com/electronics/schematics/audio/sunnconcertbass.pdf

[aron]

I don't know. This is a major undertaking. OK, for starters, build an audio probe and "listen" to every gate of each transistor in the preamp. Alternately, you can listen to the signal at the coupling cap coming from the drain of the transistor. (C103,C106,C109)  I don't even see the distortion "channel". Alternately, measure the drain of each transistor and see if any of them seem way out of range with regard to the other.

One of them will make the crackling signal is my guess. Hard to tell. Someone else can probably figure this preamp out better than I can. I don't know what the dual distort really does.

[soulsonic]

Sunn Concert Bass you say? Just so happens I've fixed a couple of those very recently. The problem is most likely with either the footswitch or the Distortion control. If either becomes dirty, it will likely begin causing the trouble you are having. Check to be sure that the RCA jacks for the footswitch is are clean and making good contact. Is the footswitch original? If not make sure that it's been wired correctly and that it has a shielded cable because signal goes through there and it can get really noisy. You should also definitely try cleaning out the Distortion pot with a good cleaner like Caig DeOxIt. When that control gets dirty, it will crackle really bad.

There's alot of little things that can cause bad crackly sounds in these amps, but 95% of them can be repaired with proper cleaning.

[aron]

WOw, maybe it is just a simple cleaning!!!!! GOOD LUCK!