Quote Originally Posted by E-Stat View Post
Only the tube in front is for the power supply. Most small tubes are of the dual triode design so one tube can function with both channels. Only a schematic would tell you the exact role. Perhaps it is the output buffer. The primary difference between 12AU7, 12AT7 and 12AX7 has do with gain with the "X" having the highest. My Manley DAC uses a pair of 12AU7s for its analog output where I use RCA cleartops.

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Well I dont have a schematic and would not know where to get one.
On the board itself there are 4 tubes. The very first one up front is for the power supply and does not go through the signal path. Then you have two tubes one in front of the other. one says "L" the other says "R" and they are 12AX7 tubes for both slots. Then you have the odd tube off to the left side thats the 12UX7...this is the tube I assume is the output tube?