I probably won't help you find your sound, but I can at least tell you what seems to be working for me after some experimentation. I also have a BM 50w, but have only had it for a few months. My musical tastes are more on the rock side of things, so adjust my settings accordingly.

I have the od trim set on about 11 oclock - I find that above that doesn't add much more to the sound except compression, although it's fun to turn it up and see what happens sometimes. The drive knob is currently between 7 and 8.

Don't forget to experiment with the main volume knob - it makes a huge difference in how the od channel works. I have mine set at 7, which just pushes the clean channel into light drive if you play hard on my strat. Also don't forget the volume control on your guitar - at these settings it can make a huge difference in your sound.

Edit: forgot to add - keep in mind that the drive circuit has it's own tone stack, and that engaging PAB cuts out the front panel tone stack, so for best results always use overdrive with the PAB on with your amp. Otherwise you're running through 2 tone stacks, which can have an adverse effect on your tone.

+1 to that and what sduck said. I keep my od trimmer between 11 And 1 o clock, and i don't push the drive control past about 6. I keep my clean channel gain between 5 and 7, clean master and OD master around 5, and use my clator as a final master, and can dial some additional gain if needed either with the drive and input controls on the clator, or via my clean boost pedal or my tube screamer dialed back.

Try different pre amp and power amp tubes as well. I currently have NOS Ge long plates in V1 and V2, for example, and they yield a nice, warm overdrive sound together with the TAD 6L6 short bottles i have currently. With a JJ in V2 it was more aggressive and gritty, but a lil harsh for my taste.

One of my fave setups (though not recommended) was 7025's in V1, V2, and V3, and JAN Phillips 6L6WGB's in V4 and V5, with my sag resistor engaged, to reduce plate voltage, and running between 46-48 ma! Again, not wise or recommended as those lil 6L6's are pushed to their limit, but the BM sounds like a cranked Deluxe Reverb or Super Reverb utilizing only the clean channel, the drive channel is useless at that point and it is semi dangerous, but fun!

By the way, I have 2 Weber 1265 Alnicos paired up with mine, and I love 'em!

Point is, the BM is a very versatile amp depending on what tubes and settings you use. Good luck and have fun!!

Gregg