The TS100 is a good amp, that's what I'm using at the moment. You wont need to use the presence knobs at all, they are a nice clean amp and the 50w a side is plenty (a bit like Marshall watts
). Channel volume issues could be a variety of things, volume pot may need a clean/spray with contact cleaner (as may input/output sockets), input tubes may need changing (how old is it ?), output tubes may need changing, maybe miss match of the output tube selector switch (you can switch between EL34 (6CA7) tubes British sound, and 6L6 tubes US sound) although this would affect both channels. Mine has 4 nice groove tube 6L6 tubes (it came like that), I would have preferred EL34s but the 6L6 tubes are fine as it's transparent, no added colour (also my preference). There are 4 12AX7 tubes for the input (1 gain 1 buffer per channel, Dougs Tubes had some advice regarding different input tube selection) and 4 EL34 or 6L6 tubes for the output (2 per channel in push pull). The output tubes on the softer channel may need bias adjustment (this is the point where the tubes swap ie one tube does the ve part of the signal, the other the -ve part, bias (predominantly) gets that xover point right). If one channel has issues I wouldn't use it (bridged or otherwise until you get it fixed). Be a shame to run it bridged when it will sound so much better in stereo.