I thought my previous made amplifier by type-19 push-pull is the best, but it was not. This time I made a single tube audio amplifier by 6SN7.
6SN7 is very popular tube and mostly used for pre-amplifier but its max plate dissipation is 5W, so indeed it can support a few-W mini pre/power amplifier by using two triode (one is pre and the other is power).
The configuration is quite similar to my previous made. The heater voltage is generated by switching 6V AC/DC adaptor, and the plate voltage (around 140V DC) is generated by direct rectifying AC 100V. YES, no power transformer.
On the top, just output transformer and choke coil, and tube are settled. I have not tried without choke coil but by the sake of this choke, it does NOT produce audible hum noise. Actual operation can be found in the following movie... Have fun!