It had to be a tube. Fired it up this morning, it was the same. Swapped out preamp tubes, powered up, problem gone. I can tap the board, no sound. I can tap the chassis, no sound. Perfect. So I played the snot out of it for 1/2 hour, thru a Celestion V30... First impressions... TMB channel, Wow, very crunchy. Normal channel, crunchier than expected. Channels jumpered, Holy Mother of Overdrive... I can't believe it!
Mesa territory gain without the fizziness. Sustain for days. Notes blossom into controlled feedback on demand. I'm delighted. Thank you Stephen. Your product has exceeded my expectations. For a first time kit build, it couldn't have turned out better.