Mono-Block Tube Amplifier
Mono-Block Tube Amplifier
- 5 tubes
- Class AB (‘ish, not quiet class AB, closer to class B)
- EL34 outputs
- Approx. 50 Watts RMS output power
- 10 Hz to 25 KHz -3 dB bandwidth
- 0.65 % THD
- Direct grid bias on output tubes
Summary
This mono-block tube amplifier is one of 5 that were developed for the vacuum tube home theater system. It is the same design as is shown in the quad tube amplifier with the exception that it utilizes a smaller power supply. 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 10 Hz to 25 KHz and a THD of 0.65 % while achieving a peak output power of approximately 50 watts RMS.
Engineering Notes, Schematics, and Plots
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.
- Mono-block Amplifier Notes
- Mono-block Power Supply Notes
- Mono-block Amplifier Design Notes
- Biasing Notes and Schematics
- Bode plot analysis and feedback loop compensation notes
- Bode plot, %THD, and peak-power data from the mono-block tube amplifier
- Bode plots in MATLAB for the mono-block amplifier. Before and after loop compensation., including closed loop bode plots.
- G. L. Charvat, “Vacuum tube home theater system (part 2), vacuum tube power amps for home theater,” Audio Express Magazine, June 2012.
- G. L. Charvat. “Design and fabrication of high-fidelity vacuum tube audio-frequency power amplifiers,” MIT Haystack Observatory, February 3, 2010.
Mono-Block Tube Amplifier Photos
Mono-block power amplifier schematic
Bode plot of open-loop transfer function before loop compensation circuitry was added.
Closed-loop transfer function of compensated amplifier.