[Diabolical Artificer]

Re balancing standing currents Chris I've tried trimmers on each valve which is a nightmare to balance, it's like trying to play whackamole.

After some thought on this there are only two ways to go to get more power, drop the UL config and bung up to 600v on the anodes or use different valves. Can't afford KT88's or 6550's but do have a few EL34's. I knocked up another temporary chassis yesterday, will report back.

That schematic is interesting, I see it uses an ECC81 as PS and no cathode followers.They usually use an ECC82 as the PS, the ECC81 has slightly less gain. I found it was hard to drive 6 valves without cathode follower's. BTW Paul, do you know what the OPT's Ra-a is on your amp?

Andy.