this issue just won't go away for me. Cesar Diaz told me to bias his amp at 52mA running classab ss rectifier. George Alessandro runs his class A amps at 60mA with 6V6's, and told me as long as I use good NOS tubes, I could go higher! I just bought a new amp that runs 4 output tubes with a GZ34 rectifier. The amp has a separate bias trim pot for each pair of tubes. A letter from the guy who built it says it can run 6V6 or EL34 (he doesn't mention 6l6) with a rebias. I started messing around with all my 6V6, EL34 and 5881 tubes, and with a little tweaking, I got a pair of EL34 and a pair of 6V6 within 3mA - sounded great! Just for fun, I replaced the EL34's with a pair of 5881's - the 5881's pull 42mA while the 6V6's pull 22mA - no hum - great tone. ???????? I also replaced the GZ34 with a 5Z4G/CV1863 - sounds great! I'd really like to hear some thoughts from Hogy, unquiet, mook, and James Peters, etc, and some of the other great builders, tinkerers, gearsluts and techs that hang out here.....please just to be clear, with this new amp I'm running a pair of 6V6 and a pair of EL34 at the same time - the pair of 6V6 pulling 22mA, and the pair of EL34 pulling 26mA - then put the 5881's in and they pull 42mA with the6V6's still running 22mA at the same time and it sounded great - much smoother breakup and great cleans - thanks in advance! p.s. - I dont know the plate voltage - I'm estimating between 350-400V?