I’ve always been drawn to headphones, but until recently, I hadn’t taken the time to fully explore designing dedicated headphone amplifiers. This latest build marks a deeper dive into that passion — and the result is an amplifier that, in my opinion, pairs exceptionally well with the ZMF Atrium.

At its core is the remarkable 71A direct-heated triode — a tube originally developed in the late 1920s by RCA as a low-power output stage for battery-operated radios. Nearly a century later, its character remains captivating.

This amplifier delivers 0.7W through a highly detailed finemet-core output transformer. While primarily designed as a headphone amplifier, it can also drive high-sensitivity speakers with ease. It truly shines with full-range, single-driver speakers without crossovers.

The circuit is configured as an integrated amplifier, using a beautiful NOS Philips E180F driver tube, coupled to the 71A via a Jupiter copper foil capacitor. Volume control is handled by the exceptionally smooth TKD CP2511 potentiometer. The power supply features three separately regulated DC filament supplies, while the high voltage is tube-rectified with CLCLC filtering. The result is an impressively quiet amplifier.

Maximum output is 0.35W into 32Ω, decreasing as impedance rises (for example, approximately 37mW into 300Ω). While 37mW may appear modest on paper, in practice it proves more than sufficient. With the ZMF Atrium, listening levels rarely exceed the 11–12 o’clock position on the volume dial.

Headphone outputs are connected to the 16Ω tap of the output transformer, while speaker outputs utilize the 8Ω tap.

Sonically, the presentation is smooth, delicate, refined, and intimate. It invites long listening sessions across all genres of music — and makes it easy to simply get lost in the performance.