Tube Audio Amplifiers Needn’t Be Complex. 25 Comments . by: Jenny List. ... It’s a conventional tube amplifier circuit in which the triode is a preamplifier for the pentode power ...

The schematic shows one channel of a stereo amplifier, and the power supply is sufficient for both channels. Transformer T2 supplies the voltages required for the vacuum tube plates. Selection of the ...

It’s one of these, an ECH83 triode-heptode, which [mircemk] has taken as the basis of an audio preamplifier circuit. The preamp circuit is pretty simple, being a two-stage single-ended design ...