Quad Tube Amplifier
Quad Channel Vacuum Tube Amplifier
- 14 tubes total
- 4 class AB (‘ish) tube audio amplifiers in one chassis
- EL34 output tubes
- Approx. 80 watts RMS output power per channel
- 20 Hz to 25 KHz -3 dB closed-loop bandwidth
- 0.45% THD
- Single power supply for all 4 amplifiers
Summary
This is the quad tube audio amplifier portion of my tube home theater system. In designing this amplifier I have attempted to squeeze as much power as I can out of a pair of EL34 pentodes while still maintaining high fidelity performance resulting in a bandwidth of 20 Hz to 25 KHz and a THD of 0.45 % while achieving a peak output power of approximately 80 watts RMS per channel.
Engineering Notes and Schematics
Caution! High voltage. Do not attempt to build anything shown here unless you have taken proper high voltage training. The high voltages present in these tube designs are deadly.
- Amplifier notes
- Quad amplifier notes
- Biasing notes and schematics
- Bode plot analysis and feedback loop compensation notes
- Bode plots and loop compensation network calculations using MATLAB
- 0.45 % measured Total Harmonic Distortion. Total Harmonic Distortion (THD) tests and analysis notes
- G. L. Charvat, “Vacuum tube home theater system (part 2), vacuum tube power amps for home theater,” Audio Express Magazine, June 2012.
- Make Magazine Blog, ‘How to designa vacuum tube amplifier.’
- G. L. Charvat. “Design and fabrication of high-fidelity vacuum tube audio-frequency power amplifiers,” MIT Haystack Observatory, February 3, 2010.