Hey Mikirob—
I have the stock tubes supplied with the amp, and have been thinking about upgrading them, so I would appreciate some recommendations. I was under the impression that the EL34 tubes were Tung Sol, but they are not clearly labeled as such. Considering that the amp ( my first tube amplifier) was only $1500, spending $500 or so in tube upgrades would be worthwhile. I asked Israel Blume if I could put in a KT77 — an EL34 equivalent — and he advised against. Thinking about Mullard or Tung Sol EL34s, and the Russian 6H9C (black base) , a 6SL7 equivalent that Dick Olsher liked with this amp in TAS review last June. Which tubes are you using? Best, Dave