This headphone amplifier consists of three ECC88/6DJ8 valves; three triodes per channel. The topology is a simple one, consisting of a gain stage and SRPP driver stage, with overall global negative feedback to keep distortion within reasonable limits. The power supply is built from two inexpensive off-the-shelf voltage converters, with the whole project running off a 19.5V laptop power supply. Total power consumption is 16 watts. Unlike most DIY valve designs, this one also incorporates feedforward PSRR enhancement for truly excellent noise performance, and double output coupling with voltage limiting, to protect headphones from DC offset.

Audio performance is excellent considering the low cost and simplicity of the design. It can deliver up to 100mW into high impedance headphones, with THD below 1% (see graph). Output power is limited to about 20mW into 32 ohm phones, but since average listening levels are less than 1mW for most headphones, this still leaves plenty of headroom.