26A7, 30V tube amp, 1/2W maybe?

[printer2]

I have a 16A7 tube which is a double pentode that has a 26V heater voltage and runs at 26V plate voltage for a rated 1/2W. I figure if using a 24V transformer and rectifying it the supply should be a little above 30V, finger safe for those hesitant about high voltage. I thought a 12AU7 would be linear enough at this voltage and a pair should be able to drive the 26A7 to full output using a 70V line transformer as the OT. Part values will probably change, just stuck in some to make the schematic look right. Three versions up for consideration and a critical eye.

[PRR]

Try all three; but my 2 cents is on the cathodyne working best *WHEN* you do it right.

[PRR]

120+120:12V power transformer is very nearly 2500:8 impedance ratio, is at least 2500 impedance at 50/60Hz so will have some bass, and PP 26A7's 40V audio on a 240V winding should be low THD. Depends whether small power iron is cheaper than small 70V speaker iron in your life. (Outside the US area, 70V line iron is rare.)

[printer2]

Thank's PRR, I just did a quick cut and paste and was not paying attention. I had a fixed bias Mosfet/fet in place at first and an extra gain stage but though it might be unnecessary for a sub-watt amp. I am unsure of a tone control also, well one can't hurt. I'll know more once I breadboard it.

[printer2]

Going to take a page out of the hifi people's book as far as a chassis. Just a sheet of galvanized steel and some spruce strapping. Will mount everything off the steel and if needed lay some aluminum tape over the wood sides and back.