Woo Audio WA6

I'm selling in very good condition my Woo Audio WA6 Gen 1 tube headphone amplifier with two spare sets of NOS tubes which will last a lifetime. I used the amp to power Sennheiser HD600, AKG K702 and K812 reference headphones with excellent impedance matching and drive.
The WA6 exhibits wonderful speed, musicality, resolution, and sound stage. Organically warms up any digital source, sounding less clinical. No surface scratches or functional issues.      
Includes Spare Sets of NOS Tubes: 6DE7, 6FD7, and two 274B rectifiers.
 
Single Disclaimer: One modification was performed to integrate gold plated amphenol RCA output jacks using silver based solder. I had implemented the WA6 as a post DAC pre-amplifier. The added RCA output jacks doesn't affect the performance or functionality of the headphone amp.

http://wooaudio.com/products/wa6.html
"Single-ended Triode Class-A, All Tube Drive, Output Transformer Coupled  In production for nearly a decade, WA6 and WA6-SE have been a critically acclaimed headphone amplifiers that deliver high-performance and offer premium build quality. Here at Woo Audio, we are committed to continuously improve our products. High performance headphone amplifier in a compact size. Realistic, warm, smooth sound. Versatile design to drive a wide range of full-sized headphones and in-ear monitors."
Technical Specifications: Headphones impedance : 8-600 Ohms Input impedance: 100 Kilo-Ohms Frequency response: 20 Hz - 30 kHz, -3dB Signal/Noise: 93 dB THD: <= 0.3% Voltage: AC 110/220 V, 50/60 Hz External dimension: 6"(H), 5½(W), 13"(D) Weight: 13.5 lbs Standard Features: Point-to-Point wiring One 5AR4 [PDF] rectifier tube. Direct substitute: 5U4G Two 13DE7 [PDF] drive/power tubes Pseudo-dual power supply All tubes. No semi-conductors in the entire circuitry High or low headphone impedance switch One 1/4" (6.3mm) headphone jack 80 watts specially made toroidal power transformer. Full aluminum die-cast chassis, anodized finish Whole aluminum volume knob and power switch button Gold-plate RCA Silver-plated hook-up wires in Telfon jacket

"All can say is wow! As you know I am a conductor of classical music and can honestly say that it is like hearing cd's for the first time - Jeffrey Milarsky, Conductor of the Columbia University Orchestra.

With a creamy, natural sound and tight bass response, along with pro-grade build quality to match, we're sure any serious music lover would enjoy this fabulous piece of audio bliss.

WooAudio has one of the prettiest and slickest build quality that you can find in the industry. Everything from the hairline finishing, the lines, the knobs, the transformer housing, all the way to the back panel, you find nothing but top quality workmanship.

It was almost magical the way the Woo WA6 made every recording sound better than I thought it was.

The WA6 offer great sound and great value! - Tone Audio, issue 8"