12AU7 / IRF612 Headphone Amplifier

Over the past few years, headphones have come long a long way. For $70 to $150 you can get a great sounding pair of headphones. Best of all, headphones allow you to get right into the music anywhere you are and you do not have to worry about annoying things like room modes and reflections. And for you do-it-yourself (DIY) audiophiles, there are also a number of great DIY headphone amplifier projects that you can choose from. Here are the details for Rogers' low voltage 12AU7 tube hybrid headphone amp.



Rogers has put together a very simple hybrid headphone amplifier for use with 32 ohm Grado SR125 headphones. His hybrid head amp uses a vacuum tube voltage gain stage which feeds a MOSFET follower output stage. The tube is a the 12AU7 (ECC82) and the MOSFET is an inexpensive IRF612. The IRF612 is configured in a typical single-ended class A circuit using a passive constant current source (CCS).

What's best about this project is the power supply. Both the 12AU7 tube and IRF612 MOSFET are set up to operate at low voltage (~12-13V). Power for this project is supplied via an external switch mode power supply (SMPS). All of the project parts are readily available and one can easily put together one about $40. Rogers has reported very good results from this very simple project.