Looking for brighter tubes

What 12ax7 and 12at7s are you presently using and which ones have you already tried? Also have you tried any KT88s in place of the 6550s?

You'd probably find the NOS German tubes to be your best bet (Telefunken or Siemens).

You should consider changing the four.22uf coupling capacitors and the two .47 capacitors. They are made in China by CBB and they are dirt cheap. That is why they use them. Not for their sound. Good for their price but easily outdone.

Siemens E81CC or ECC81 have nice extension.

the weak link in this amp are the coupling caps. don't waste money on tubes till you fix the caps followed by a power supply upgrade.

Not sure about the power supply but the caps were Maryland Jolida upgraded (along with other items in the "upgrade" mod version). The 12AT7s currently are EH Russians (the only non-Tung Sols).

The amp is new-ish (newest version actually, and supposedly improved over older versions), I haven't tried any other tubes in it yet, but so far it sounds great (quiet, looks cool, very well built, sweet tone). I'm not complaining, just fishing for info among my fellow tubists. Tubers? Tuboids? Bottle Heads? Valvers? At the current price for these new, I'm surprised everybody doesn't own one just to play with the damn thing. It's fun. I appreciate the suggestions...keep 'em coming.