Sergei Klimanski
Yesterday the warranty expired (1 year) for a tube amplifier (with phono preamplifier) from the very famous Japanese company Audio Note, which I bought in Riga in one of the High-End stores.
If you read the description, this device is assembled according to the PP circuit on 12AX7/EL84. What did I see when I opened the lid? Four 6P14P tubes from the Saratov plant, manufactured in 1978, and one of them had a very shabby appearance (heavy deposits opposite the windows in the anode, and the terminals were corroded. In the build-up, both in the phono preamplifier and in the preamplifier in front of the 6P14P there were 12AX7 Yugoslavian production with flat anodes. The amplifier sounded generally good, but I replaced the 6P14P with EL84 JJ, and the Yugoslav valves with 12AX7LPS Sovtek. Even without adjustment, the amplifier finally sounded wide, before that the sound was somehow compressed, flat, as if there was not enough air. I love this lamp - 12AX7LPS - in my opinion, this is one of the best 12ax7. Now all that remains is to adjust the phase inversion stage - there are potentiometers on the board. Below is a diagram that I managed to restore on the outer part of the printed circuit board (of course, I am not the device disassembled, so missing parts are possible
