All Tube 20 Watt Audio Amplifier
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All Tube 20 Watt Audio Amplifier

All Tube 20 Watt Audio Amplifier


Published: April 29, 2018 2 0 435
By: Joseph Erdy, Cal Poly San Luis Obispo
Category: Engineering
Hashtags: #Analog #AnalogCircuitDesign #Audio #audioamp #audiodesign #audioengineer #Design #Electrical #Engineering #hifi #Mechanical #MechanicalEngineering #Music #Project #Solidworks #Tubes #vacuumtubeaudio #vacuumtubes

This power amp was an experiment in designing an all-vacuum tube circuit. We take transistors for granted in this day and age, and I wished to see how challenging it would be to design a circuit that didn't have any "sand" in it. The result was a hot, heavy, power-hungry behemoth. The choice of output tubes limited the output power to 20 Watts, which was a fraction of the power being consumed. Nearly 100V is blown across the vacuum diode rectifiers under full current load, which is incredibly wasteful. Sound tests revealed clear sound. However, the power supply sagged significantly under heavy signals (around 20Hz). The gas regulator tubes couldn't sink enough current to balance the increase in screen current draw from the output tubes.
This amp was a fun experiment, but was ultimately scrapped in favor of a more efficient project.


Adam Markowitz Ashley Hyman