by Antony Chazapis

My take on an Internet classic. The DIY Audio Projects hybrid headphone amplifier. Read more info on the design here, and many interesting implementations at the forum page. I have had great success with another project from the same site many years ago – my first tube amplifier. This was built as a gift for a good friend.

Headphone amplifier decomposed

The amplifier uses very few parts. I already had a 12AT7/ECC81 tube from some hamfest. The output MOSFETs and LM317 regulators where mounted on a CPU heatsink, using an M3 tap. The enclosure was spray-painted red. Most components were soldered directly on the tube socket and the output jack. To power the amplifier from a 13.8V power supply, I placed two diodes in series with the power input. Thus I got about 12.6V at the tube filament.

I don’t have the experience to accurately comment on the sound, so don’t expect a thorough critique. I can just say I like it.