Sorry this ran so long...if you're in a hurry, try the last paragraph... So, few years (like 6) ago, my 100 watt 1970s all-tube bass head went FZZZT on me while at home, practicing. Ok, it happens, bust out the backup and carry on. http://www.univox.org/pics/amps/1051.jpg At the time I knew which parts were the tubes, but that's about it. I extracted the 4 6L6GCs and stuck in a quad of EL34s I had lying around and fired it back up...bupkus. So, I stuck it under the bench and ignored it. About 2 years ago I got it out (I now know how to tell caps and resistors apart!) and looked it over. It 'works' again, but is obviously not healthy. I haven't a clue where to begin, so I take it to my local tech. Now, when the amp konked out, it was loaded with a trio of NOS 12AX7s and a reltively new set of JJ 6L6GCs. I played it in a 5-piece band with a heavy-handed drummer, a 55 watt Mesa and HRDx. I can literally dime every knob, back off the treble & presence a touch and I get beautiful, vibrant clean tone. Shouldn't have worked like that, I know, but it did. Now, I've gotten it back, 'repaired'. And it does seem to function properly now, which it didn't before. But now it's a guitar amp. If I crank it, it distorts, even with a tele. Tech tells me that all the tubes are plenty strong (though one 6L6 is a touch microphonic). Kinda bummed I don't have a bass amp anymore, but I'll tweak for that later. Here's the funny part...just for reference, the amp has a control panel that pretty much mirrors a Tweed Bassman: 2 norm inputs, 2 guitar inputs, vol1, vol2, bass/mid/treb/presence. And, cause it had never occured to me before, I tried jumpering the channels, and I noticed something funny... If I turn either volume up all the way, I get loud. I then bring the other volume up and get a little more volume and a "fattenning effect"...but when the 2nd vol hits about 7-8, the amp gets noticeably quieter! If we assume that the knobs "go to" 10, and add the two together, any 'sum' over 17 or so seems to yank the rug out from under the thing. Both on 8, really loud...both on 9, much quieter. Any ideas?