The TSL has 'leads' in the back that you can connect a meter to and adjust accordingly. The post I saw from some forum somewhere that I lost (thinking I'd easily find it again) had specific step by step instructions as well as the proper settings. I've never done it myself before but I'm pretty handy and have read up on all the danger/methods etc. (things I should have known a long time ago, I guess I've been lucky so far in the tinkering I've done with other amps) Since this amp provides a simple avenue I am planning to do this myself once my new tubes arrive-