Edit: Tom (@tomchr ), the designer, has circumvented the embargo and has posted himself So I was wandering on the page of one of my favorite DIY suppliers when I see this: http://www.neurochrome.com/product/hp-1-ultra-high-end-headphone-amp/ I like that he offers options from the PCB alone all the way to a fully assembled product. Although one thing that I think is a bit odd is that the fully assembled PCB is $850 and the chassis is $200. That adds up to $1050, however the fully assembled product is $2200$1499. Anyway, he has a really good reputation for his amp builds so I am curious how he approaches headphone amps. I thought about buying the PCB and adding it to my pile of unfinished projects, but at $200 I can't just let this sit around. Some additional info: http://www.neurochrome.com/hp-1-ultra-high-end-headphone-amp/ Spoiler: Features [*]Fully optimized 4-layer circuit board. [*]Total harmonic distortion: 0.000032 % (200 mW, 300 Ω). [*]Total harmonic distortion: 0.000050 % (200 mW, 32 Ω). [*]Total integrated output noise: 1.0 µV RMS (A-weighted, 20 Hz – 20 kHz). [*]Output power: 3.0 W (32 Ω). [*]Output power: 450 mW (300 Ω). [*]Gain selectable (+6, +12, +20 dB) by front panel switch to accommodate a wide range of sources, including smartphones, tablets, DACs, and CD players. [*]1/4″ phone and 4-pin XLR output connectors. [*]Balanced (XLR) and unbalanced (RCA) inputs. [*]±0.1 % tolerance Susumu RG-series resistors used in critical parts of the circuit to ensure the best possible performance. [*]All signal switching is accomplished using relays with gold plated switch contacts. [*]ALPS RK097 volume control potentiometer. [*]Well filtered switching power supplies followed by onboard low noise linear post-regulators ensuring the highest power supply performance. [*]Protection against DC voltage on the amplifier output. [*]Integrated mains soft start and 320 Joule surge suppressor. [*]ON indicator emitting a subtle and pleasant blue glow. [*]International mains voltage compliant (85 – 264 VAC @ 47 – 440 Hz). [*]All aluminum chassis made in Canada. Judging from the ridiculous THD numbers and the measurements he has posted, it looks like the ultimate expression of an objective amp. Audio pros and reviewers would probably be interested in an amp like this.