12AU7 Tube / IRF510 MOSFET Hybrid Headphone Amplifier

Rogers has improved upon his 12AU7 (ECC82) Tube / IRF612 MOSFET Headphone Amplifier project from August 2008 with a new version, the NP-100v12, a DIY 12AU7 (ECC82) Tube / IRF510 MOSFET Headphone Amplifier. The 12AU7 / IRF510 headphone amplifier is powered from a rechargeable 12V sealed lead acid (SLA) battery which makes this an ideal project for novice builders as they don't have to worry about the high voltages typically associated with vacuum tubes. The headphone amplifier circuit is very similar to the previous build utilizing a single 12AU7 (ECC82) vacuum tube for the voltage gain stage which is followed by a IRF510 MOSFET follower stage which supplies current to drive demanding headphones. IRF610, IRF611 or IRF612 MOSFETs will also work in this circuit. The main difference between the updated headamp and the the original version is that a LM317 regulator (used as a constant current source (CCS)) is used in place of the load resistor to bias the MOSFET follower into class-A operation.

Included in the project documentation are printed circuit board (PCB) images and Eagle circuit board files so builders can easily make their own PCB for this project. Being a fairly simple circuit, one could also easily build the headphone amp point-to-point on a 750 hole protoboard. This simple headphone amplifier can be built for about $40-50 or less if you recycle parts and and enclosure.