Matrix M-Stage HPA-3U USB DSD Headphone Amp Dac

Matrix M-Stage HPA-3U USB Headphone Amp and Dac Combo.  This is the original 3U with the TI DAC (I believe they later went to Cirrus Logic.)

I enjoyed the sound from this and it's a very nice DAC/Amp combo.  DSD support was a plus as well which, to my ear, generally had a smoother more refined sound. 

Features/Specs below.  Includes box, power cord, manual and disk- I don't recall if it came with a USB cable or not but that is not included.  It's rated in very good condition- I was tempted to go higher.  I'd  encourage one to look at the pictures to judge; there is one nick that is shown.

Features:

Revolutionary Improvement
HPA-3U
is a biggest evolution since the M-Stage series headphone amplifier
came out, the new appearance, the new circuit design and radical
performance improvement to make it all difference.

THD+N＜0.0003%
Full-band
of THD + N less than 0.0003%, SNR up to -112dB, bandwidth not less than
150k at -3dB gain, 0.2Ω ultra low output impedance, three gain level
options to fit for the different impedance and sensitivity headphone,
all of these excellence performance improvements to be born the brand
new HPA-3U!

High Resolution Format Compatibility
The
most stable XMOS U series USB controller on the new USB module, support
24 bit/192kHz sample rate PCM signal playback, DOP mode DSD playback
capacity, the biggest bright spot is that can be played with your iOS
and the most Android devices.

Brand New
Excellent
structural design to quickly dissipate the heat of power tube via the
shell, to ensured the stability of the work; full symmetric circuit
layout makes two channels audio have the isometric path; driver stage
use the precision constant current source and establish stable working
point; Parallel output of the output stage can effectively reduce the
output impedance, and improved driving capability, extended dynamic
range.

Best Selection Best Match
Alps
27 series volume potentiometer, Wima and Nichicon audio
gradecapacitors, Noratel toroidal transformer, precision non-inductive
resistance, each carefully selected components make HPA-3U not only
presents the perfect sound, but also a more stable and reliable.

Specification:

Line Output
SNR: ＞-112dB at 20Hz-22kHz A-Weighting
THD+N: ＞0.0003% at 1kHz 1VRMS A-Weighting
Frequency Response: 20Hz-20kHz(+0.01dB/-0.04dB)
Output Impedance: 51ohms

Headphone Output
SNR: ＞-112dB A-Weighting
THD+N: ＜0.0003% at 33ohms 90mW 1kHz A-Weighting
Frequency Response: 20Hz-20kHz(+0.01dB/-0.04dB)
Output Impedance: 0.2ohms
Output Power: 2800mW at 33ohms / 420mW at 300ohms / 210mW at 600ohms at THD+N=0.01%

Gain Control
Gain: 5=5dB 10=10dB 20=20dB

USB Input
USB Chip: XMOS U-Series Asynchronous USB Chip
D/A Chip: Texas Instruments DSD1793
SNR: ＞-110dB A-Weighting
THD+N: ＜0.002% at 1kHz A-Weighting
PCM Sample Rate: 16-24Bit /44.1kHz 48kHz 88.2kHz 96kHz 176.4kHz 192kHz
DSD Sample Rate: DSD64（DoP）
System Support: Windows XP/Vista/7/8/8.1 systems need to install the driver supplied
Mac OS X 10.6.4 and above version have native support and do not require a driver
Can be used with the most of Android devices via the OTG cable
Can be used with iOS devices via the Lightning to USB Camera Adapter

Power
Power Voltage: 230V position is fit for AC220V-240V 50/60Hz
115V position is fit for AC100V-120V 50/60Hz
Power Consumption: ＜25W
Fuse: AC250V/500mA 5×20mm

Others
Dimension: 285×142×49mm L×W×H(Including the protruding part)
Weight: 1.7kg

Package:
1 x M-Stage HPA-3U
1 x Power Cord
1 x Driver&User Manual Disk