A simple tube headphone amplifier

A simple tube headphone amplifier

Recently, I welded a tube headphone amplifier, and chose a famous tube 6c45 with high amplification factor and low distortion as power amplifier. It has suitable output power with only single-stage amplification. See the attached figure for the circuit.

This is a typical triode amplifier circuit.

There is no AC negative feedback. The input signal is added to the gate of the tube along the potentiometer RP, and through amplification, the screen loop generates a pulsating current that changes with the input signal and flows through the primary of the audio transformer. After impedance transformation, a signal suitable for driving low-impedance headphones is obtained at the secondary.

Friends who have the conditions can wind the output transformer by themselves. Its primary impedance is 3.5kΩ. The three transformers are covered with stainless steel cups without handles, which can shield the leakage magnetic field and look beautiful.

RP uses a domestically produced Fengzhisheng brand double stepping potentiometer. Other components in the circuit are selected as shown in the figure.