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A JFET-MOSFET Headphone Driver

2016-02-14 20:18  
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This headphone buffer is based on Greg Szekeres' MOSFET Headphone Driver. It is a robust and reliable zero feedback, class A circuit. [Editor: And like the Szekeres MOSFET amp, this amp has unity voltage gain. Therefore, the audio source must supply adequate voltage to drive headphones.] The power supply is choke regulated. The circuit is configured for low impedance headphones like my 32-ohm Grado SR60s. Greg's circuit was designed to be driven from the output of a preamplifier, as high frequency rolloff will result when a volume control feeds directly into the IRF510 MOSFET, due to the MOSFET's high input capacitance.

The rolloff in the Szekeres amp is audible, but would not worry many listeners, since it tends to make for a smoother, more powerful sonic presentation overall. It is avoided if the MOSFET is driven by a JFET cathode follower with low output impedance. A JFET follower also has a high input impedance, making it an excellent input stage. Due to its flat frequency response, low noise, soundstaging, tonal balance and lack of grain, I recommend the circuit, and feel that it can - with patience - be developed into a reference class component. The amp can be tweaked to sound bright or dark, warm or cold.

A JFET-MOSFET Headphone Driver