Most audio tube amps we see use common tubes – usually a 12AX7 for the preamp and one of the more common power tubes such as an EL34.[Daniel], on the other hand, decided to build his own audio tube amp with a 13EM7, a tube originally used for a television’s vertical oscillator. The resulting project is a wonderful stereo amp that sounds really good, to boot.
[Daniel] picked up the idea of using a 13EM7 tube from [Fred Nachbaur]‘s MiniBlok SET amplifier. This very tiny 1-watt tube amplifier uses a single tube originally designed for use in old, old televisions. The secret behind this build is the fact this tube is actually two triodes in one package; one side of the 13ME7 has tons of gain but not much power, making it perfect for a preamp. The other side has a lot of power, useful for delivering two watts of power into a speaker.
After [Daniel] etched a few boards for his amp, he milled out a piece of wood for the chassis. When everything was mounted he had an awesome looking stereo amplifier that also sounds great.