I use 12au7 in my Primaluna Integrated Amp. I have tried several combos with the Mullard Reissue El34’s and GL KT77 Russian. I much prefer the KT77 sonic balance over the Mullard.
What I have found is that the Mullards have too much midrange forwardness and the KT77’s are much better balanced from top to bottom. More extension top to bottom,.the midrange is clearer and not forward.
For the Preamp section I like the combo of either the (2) Cifte or Tungsram in the Gain stage and the (2) NEC/Mullard in the first Driver Stage. The second driver stage I use the stock (2)12au7 Chinese tube.
What I have found is that the Mullards have too much midrange forwardness and the KT77’s are much better balanced from top to bottom. More extension top to bottom,.the midrange is clearer and not forward.
For the Preamp section I like the combo of either the (2) Cifte or Tungsram in the Gain stage and the (2) NEC/Mullard in the first Driver Stage. The second driver stage I use the stock (2)12au7 Chinese tube.