I had try some 6u8a, 6gh8a, 6an8 tubes as phono preamp, I had around 10 tubes most are 6gh8a,
I build a phono preamp ciruit and found out very hard to match a pair of tube for good gain balance for L/R channel. I used the pentode and triode on the same tube.
I give up on the experiment as I don't had to much tubes to match. I think what is the
other way to take care this issued. Then I try just to match the gain on the pentode section only of each tube, I can get few match pair
I build the phono preamp again with 6gh8a pentode follow by a half 12au7, and use the 6gh8a triode as a cathode follower and the result looks good.
I had test 12au7, 12at7, 12ax7 for the triode section, all those tube works, only with different gain. I think the circuit will works with all 12xx7 tubes.
I build a phono preamp ciruit and found out very hard to match a pair of tube for good gain balance for L/R channel. I used the pentode and triode on the same tube.
I give up on the experiment as I don't had to much tubes to match. I think what is the
other way to take care this issued. Then I try just to match the gain on the pentode section only of each tube, I can get few match pair
I build the phono preamp again with 6gh8a pentode follow by a half 12au7, and use the 6gh8a triode as a cathode follower and the result looks good.
I had test 12au7, 12at7, 12ax7 for the triode section, all those tube works, only with different gain. I think the circuit will works with all 12xx7 tubes.
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You can't tube roll a phono stage, the plate resistance is part of the EQ, your RIAA EQ changed with every different tube you tried.