I recently have been gaining interest in valves/tubes, and their operational use. So I went to eBay and bought a cheap (but decent-looking) $197 stereo valve amplifier so that I could build my own valve amp and possibly learn how tubes operate in application.
This amp is using a Russian 6N2P (sometimes called a “6H2n”) and a pair of Chinese 6P1 tubes. The schematic only shows the left channel connected, but the right channel is connected the same except on different pins of the ‘driver tube’ (if that’s what it’s referred to as). My main question is how this operates; Where is feedback? Why is there no isolation from the input to the tubes (capacitor isolation is used in transistor amps to prevent voltage going into the input source and to let AC pass into the transistor)? Why does it need a driving tube to drive the main channel valves?
I hope to learn more about tubes, they are a very interesting piece of history and are quite nice to play around with.
How to read the schematic:
-The left audio channel is connected to pins 1, 2, and 3 on the 6N2P tube. The right channel is connected to pins 6, 7, and 8 on that tube.
-The heating filaments are connected in parallel, and all tubes utilise pins 4 & 5 as the heater filaments.
-To change the mains input voltage of the transformer (to accommodate your country’s voltage), connect the primaries in PARALLEL for 110-120v, or connect the primaries in SERIES for 220-230v. (Mine is in the 110-120v configuration, obviously).