The amp has some mods, mostly increased filter capacitance, Mercury Magnetic output transformer, and coupling caps adjusted to let more low end through. I also have a Bandmaster which has gotten a similar treatment, along with a negative feedback adjustment pot. The Showman functions great, it has Philips 7581As in it and sounds wonderful. The only thing that's odd is that the bias current fluctuates as I measure it, maybe by 10-15%. The Bandmaster is dead stable. Any ideas what could cause this? I'm not noticing any real issues with the amp, in fact, it can get pretty loud and stay really clean through my Sunn 200S. Oh yeah, oddity #2 is that the vibrato channel is quite a bit lower in gain than the normal channel. I've tried switching out the preamp tubes, but no change. I expect some difference, due to the vibrato circuit, but this seems to be quite a bit more than I expected. Thanks for any ideas! I do love this amp.