I think I've resolved to just take it into a shop here in Vancouver but let me know if you have any advice. Here's the story: Four days ago I got a 4 ohm 210xlt. I played my 400rbIII into it for about two days. Prior to that I was running it only 8 ohms. Two days ago my 400rb shut down on me until I restarted it. Then it played fine again. Yesterday, in practice right before my gig, it died. I tried checking/switiching my bass (passive), the patch cables, the power cable, the speaker cable, the cabinet, nada. So I tried running direct out to our PA going post eq and the preamp seems to be working fine (albeit not as pleasing as just running pre eq). The PA puts out good sound. If I run it as I would normally (no PA) and crank it ( I mean more than I would ever normally) it puts out a weak, crackly, horrible pseudo bass sound. I tried the ol' 'jump the effects loop' with a cable and no luck. So I figure my power amp has something wrong with it. Any tips, suggestions?