Tubes

[thoven0215]

Is it possible to use 6sn7 instead of 12at7? If so, would I have to use an adapter or can I just rewire the connections that go to the 12at7 to a 6sn7? If I can do that, how would I go about rewiring it? Thank you.

[Paul Birkeland]

You're going to lose a whole ton of gain if you do that, and you will definitely not be able to get the Stereomour to make full power with a standard 2V DAC using a 6SN7.

[pboser]

There are a number of the 12a*7 tubes that have octal equivalents, but my quick research shows that the 12at7 isn't one of them.  I'd go with PB's advice - or at least forge ahead informed by it.
Also you'd have to use an adapter, as you mentioned, or make the tube socket bigger to fit the octal socket.

[Paul Joppa]

The 6CG7 and 6FQ7 are 9-pin versions of the 6SN7, requiring only a change in the heater wiring.  The 6SN7 is (as has been pointed out) an octal, which would require an adapter or major surgery to install and wire a suitable socket.

The driver plate current should be increased, using 130 ohms for R1 in the C4S (instead of 150 ohms). The bias should be increased, using 1000 ohms cathode resistor (instead of 365 ohms). You would need about 3.75 volts rms to drive the amp - about 9dB more than stock.

[Paul Birkeland]

You would need about 3.75 volts rms a preamp to drive the amp