Dual-monaural USB DAC that supports 11.2MHz DSD with
built-in fully-balanced/parallel-unbalanced headphone amplifier
DAC with dual-monaural structure is even more advanced
High-performance VERITA AK4490 DACs support 11.2MHz DSD
and 384kHz/32-bit PCM
For DAC chips, which are the keys to digital audio, we have used VERITA AK4490
DACs, which are made by Asahi Kasei Microdevices Corporation and have an
established reputation for use in high-end audio equipment.* The VELVET SOUND
architecture provides the fine expressive capability suitable for the playback
of high-resolution audio sources that reproduce sound waves outside the human
audible range. Furthermore, a newly developed low distortion technology enables
performance of S/(N+D) = 112 dB. This is the best level in the industry for a
120dB class DAC.
Not only is native playback with direct processing of
11.2MHz DSD signals possible, support is provided for an even greater variety
of high-resolution audio sources, including 384kHz/32-bit PCM digital input. We
have realized expression of the fine smooth detail and outstanding sense of
sound placement that characterize high-resolution audio sources.
*The AK4490 is a product in the Audio4pro™ family brand
developed by Asahi Kasei Microdevices Corporation for professional audio
equipment and high-end digital audio applications.
Dual-monaural structure supports fully-balanced
transmission and realizes further advancement
Behind the expressiveness of the UD-503, which exceeds the level expected
of its class, is an indulgent dual-monaural circuit structure that encompasses
every aspect from the power and D/A sections to the analog output stage.
Starting with the toroidal core power transformers, which
feature the ability to supply stable current, and the high-performance VERITA
AK4490 DACs, the dual-monaural structure has a complete mono circuit for each
channel. This prevents the signals from interfering with each other as much as
possible. Interference is suppressed between the left and right channels, which
is particularly important for headphone listening, so this unit can also be
used as a high-performance headphone amplifier.
Furthermore, by processing the output signals of each
channel completely with a differential from immediately after D/A conversion to
the final output stage, common mode noise is removed and the sense of air that
high-resolution audio has is not lost in transmission during balanced output.
In addition to 44.1kHz and 48kHz internal clocks, 10MHz
external clock input is also supported./dt>
When connected by USB, rather than synchronizing with a computer clock that
is unstable and noisy, the UD-503 supports asynchronous USB transfer mode,
allowing it to control PCM and DSD signals by synchronizing with its own clock
generated by its built-in high-precision crystal oscillator. Two dedicated
internal clocks running at 44.1kHz and 48kHz are built in. By applying clock
from an audio grade high-precision crystal oscillator, which features low phase
noise, to input signals which that sampling frequency are whole number
multiples, the effect of jitter on audio quality can be largely suppressed and
the audio source can be reproduced faithfully.
In addition, with support for 10MHz external master clock
input, synchronization with master clock signals of even higher precision is
possible. By synchronizing with clock that has an even higher precision, you
can enjoy changes in tone quality and improved audio quality that can be felt
DSD Up-conversion function using a custom chip
Using an FPGA (programmable IC) of our own design that utilizes a fluency
algorithm to smoothly augment digital audio signals, in addition to the 2x, 4x
and 8x upconversion of PCM digital signals, DSD up conversion is also
supported. Using this, you can easily experience the dense sense of air that
DSD files have even when listening to CDs from your collection.
You can up-convert 44.1kHz/16-bit audio files ripped from CDs up to 11.2MHz DSD
format files, which have about 256 times the amount of data as the original CD
files. 48kHz PCM audio files can be played back in 12.2MHz DSD format.
Four types of PCM digital filter and two types of DSD
In addition to four types of PCM digital filters and an OFF mode, the unit has two types of DSD digital filters, so you can choose the best filter for the input file format and type of music. You can enjoy the subtle sound nuances of different filters without needing to connect different USB DACs.
An FIR filter with a steep roll-off sharply cuts signals outside the audio band.
An FIR filter with a slow roll-off gently cuts signals outside the audio band.
A short delay filter with a steep roll-off sharply cuts signals outside the audio band.
A short delay filter with a slow roll-off gently cuts signals outside the audio band.
Isolation circuit that completely separates the grounding
of the digital and analog sections
Between the digital and analog sections, the circuit design uses a digital
isolator to completely isolate both the power supply and the ground. So, all
noise coming from digital input sources, starting with noise from the computer
via USB, is prevented from entering the analog section by way of the power line
or the ground. An isolation circuit offers significant benefit particularly
when playing high-resolution audio sources with high sampling rates. The UD-503
is the first product in our Reference Series to include one.
Independent high-capacity toroidal core power
transformers for left and right channels
Both left and right channels each have one dedicated high-capacity toroidal
core power transformer that supplies stable current. This is also a
continuation of the dual-monaural design and enables the stable supply of
current to each channel without being influenced by the changes in current
consumption due to processing of the other channel's signal. Even though it is
small, we have incorporated approaches that are used in much larger high-end
Analog output circuits that have been further improved
Our original TEAC-HCLD output buffer circuit, which is a
Current-Enhancing Output Buffer circuit
In order to transfer music signals to output devices without losing their
great dynamic range, we have included TEAC-HCLD (High Current Line Driver)
circuits. These increase the current transfer capability that is crucial for
analog output circuits.
We have applied the expertise that we have gained in the
design of audiophile equipment, and for each channel side included two buffer
circuits with high current transfer capabilities. By using differential drive
for balanced output and parallel drive for unbalanced output, we have increased
current transfer capabilities, allowing the transfer of music signals without
losing their dynamism.
Preamp circuits now use TEAC-QVCS high-precision volume
control with a four-circuit structure
The UD-503 can also be used as a preamp. One pair of XLR balanced outputs
and one pair of RCA unbalanced outputs and included and can be set to either an
adjustable or a fixed volume level, allowing a simple system to be put together
in combination with a power amplifier or active speakers. We have even
considered connection of record players such as the TEAC TN-300 turntable,
cassette decks and other analog sources with line outputs by also including one
pair of analog RCA inputs.
For the preamp circuit, we have utilized the TEAC-QVCS (Quad
Volume Control System), which is a circuit with a fully-balanced design that
uses balanced processing of the audio signal at every stage from immediately
after conversion from digital to analog until it reaches the volume amplifier.
Control signals transmitted from the volume knob
simultaneously adjust the variable gain amp type volume controls for a total of
four independent circuits—positive and negative for both of the left and right
channels. Using this system, the unnecessary manipulation of audio signals is
eliminated, and the left/right and positive/negative independence of the audio
signals is preserved, achieving clear sound quality with outstanding channel
separation. (This does not apply when using unbalanced analog input.)
This volume control system realizes 256 steps of volume adjustment in 0.5dB
increments over the complete range from −95 dB to +24 dB. Precise volume
adjustment has been made possible using a remote control, which is difficult
using motorized analog volume. In addition, optimal volume levels can be
achieved for headphone listening, which requires precise volume adjustment,
using headphones with various levels of efficiency.
Volume display using OELD has excellent visibility
The organic electroluminescent display (OELD) with a 4-level dimmer
provides high contrast and excellent visibility. A large font is used to enable
listeners to check the volume even from distant positions.
Headphone amplifier that brings out even more of the
potential of headphones
Headphone amplifier with discrete construction supports
balanced drive headphones
The connection of balanced drive headphones is enabled by also using for
headphone output TEAC HCLD circuits that are for line output and are composed
of 4 output transistors each for both left and right channels. Furthermore,
even during single end use, drive that is much stronger than an ordinary single
end headphone amplifier is possible by making these transistors operate in
parallel. In this unique circuit design, due to the AB class amplifier that
greatly expands the A class operating range, A class operation is used for most
of the range used in ordinary headphone listening. The potentials of various
types of headphones can be brought out, starting with 600Ω high-impedance
On the front of the unit, two 3-pole TRS (standard stereo)
jacks are provided as headphone outputs. These can be switched between three
types of drive operation. In addition to connecting balanced drive headphones,
you can also use unbalanced drive to connect two pairs of ordinary headphones,
as well as use active ground* drive, which can further decrease noise during
silences and enhance the expressiveness of delicate sounds.
Introducing a new drive method for headphones: active
The active ground method is a drive method that, using the same connection
method as balanced connection, forcibly sets the COLD to stable 0V with an
amplifier circuit that connects the COLD to the ground. Not only can a ground
that is closer to the ideal be achieved than when using the general grounding
method, this method has the effect of suppressing the influence of hum from the
power supply. Since the noise floor is lowered and silence enhanced, the
breathing of artists and the textures of sounds can be felt even more
Enclosure designed with great attention to detail
The full-metal body realizes both vibration control and
elegant style in an A4-size body that enables placement on a desktop
The construction of the entire body from metal panels that are effective
against external noise suppresses the penetration of electromagnetic noise
emitted by computers and other devices. This realizes a clean internal
environment with low noise even when the surroundings are hostile to audio
equipment. The metal chassis is also wrapped from both sides with 8mm-thick
aluminum panels, and a center beam connects the front and rear of the chassis.
These features prevent twisting and bending to realize a strong and stable
In addition, the footprint that is the size of a page* allows it to be placed
on tables, sideboards and other small spaces.
*Not including jacks, knobs and other protruding parts.
Symmetrically placed XLR output and RCA input and output
The output jacks on the rear panel, including metal-plated XLR jacks for
balanced output and RCA pin jacks for unbalanced output, have been
symmetrically located for the shortest signal paths. The unit has been designed
for connection with high-end equipment. For example, the left and right pin
jacks have been placed with enough space between them to enable the connection
of large-diameter RCA pin jacks.
In addition, three digital inputs on the rear panel (USB,
coaxial and optical) are complemented by one (combined coaxial/optical
connector) on the front. Starting with 192kHz/24-bit using the coaxial and
optical digital inputs, the input of 2.8MHz DSD using DoP and other
high-resolution signals is supported. The digital input on the front is a
combined coaxial mini and optical mini connector, making it simple to connect a
TEAC HA-P90SD or other portable digital audio player capable of digital output.
(A coaxial-3.5mm mini conversion cable is included.)
Three supportive pinpoint feet that allow easy
The three-point support method used for the legs enables stable body
installation without influence from even the slightest surface irregularities.
An original structure that unifies the spike-shaped foot with the mortar-shaped
foot-stand is used for each leg. Vibrations and resonance are reduced by
supporting the body of the unit on pinpoints. This thoroughly eliminates mid
and low frequency heaviness and murkiness and realizes improved resolution,
which brings out the details of sounds and sound placement.
Each pinpoint foot used on the UD-503 is composed of the foot
(top of photograph) itself that is attached firmly to the chassis, and a foot
base (bottom of photograph). The base flange (the outer rim of the
mortar-shaped part) hangs from the flanges of three screws. Due to this
structure, the interlocking flanges prevent the feet bases from falling off or
shifting when the body of the unit is lifted. When the unit is placed, each
spike point touches only the single deepest point in the mortar-shaped part of
Although the pinpoint method has been called the ideal for
audio equipment feet, complete installation had been extremely difficult. With
this structure, we have made installation using this method simple.。
TEAC HR Audio Player, which supports 11.2MHz DSD playback
on both Windows and Mac, provided for free
11.2MHz DSD files can be played back easily using Windows or Macintosh
computers without making complicated settings. The next-generation of
high-resolution audio sources can be enjoyed immediately. (When using a Windows
computer, a separate driver must be installed.)
DAC that supports 11.2MHz DSD and 384kHz/32-bit PCM
circuit structure used from the power supply to the digital and analog
left and right channels have their own high-end AK4490 DACs, which are
made by Asahi Kasei Microdevices Corporation
high-capacity toroidal core power transformers—one each for left and right
circuit that completely separates the digital and analog sections
TEAC HCLD buffer amplifiers, which are current-enhancing output buffer
circuits, are used for the line amplifiers
to formats up to 12.2MHz DSD and 384kHz/32-bit PCM using an FPGA
(programmable IC) that utilizes a fluency function
types of DSD filter and four types of PCM digital filter, as well as an
external clock input supported (available during USB asynchronous
high-precision internal clocks—one each dedicated to 44.1kHz and 48kHz
signals (available during USB asynchronous transmission)
pair of RCA analog unbalanced inputs
output can be set to fixed, fixed +6dB or variable for the one pair of XLR
analog balanced outputs and one pair of RCA analog unbalanced outputs
jack polarity can be set (2 HOT or 3 HOT)
QVCS high-precision volume circuit
digital volume display with excellent visibility and remote control with
one-button operation of various functions
display shows input signal type and various settings (with 3-level dimmer
and off functions)
drive headphone amplifier with discrete construction and maximum output of
700 mW + 700 mW
amplifier can be switched among 3 drive types: unbalanced, balanced and
inputs on the back include one USB, one coaxial and one optical
coaxial mini/optical mini digital input connector on front is convenient
for digital input from portable devices
power consumption design and automatic power saving function meet modern
full-metal body realizes both vibration control and elegant style in an
A4-size body that enables placement on a desktop
original design for three-point support using pinpoint feet with attached
|Specifications||Digital Audio Input Coaxial Connector RCA jack x 1 1/8" (3.5mm) Mini jack x 1 (compatible with Optical Input) Input Level 0.5 Vp-p Input Impedance 75 ohms Supported Format DSD, PCM DSD 2.8MHz (176.4kHz/24bit DoP transfer) PCM 32k / 44.1k / 48k / 88.2k / 96k / 176.4k /192kHz, 16 / 24bit Optical Connector TOS link x 1 1/8" Mini Optical jack x 1 (compatible with Coaxial Input) Input Level –24.0 to –14/5dBm peak Supported Format DSD, PCM DSD 2.8MHz (176.4kHz/24bit DoP transfer) PCM 32k / 44.1k / 48k / 88.2k / 96k / 176.4k /192kHz, 16 / 24bit USB Connector USB B type x 1 Supported Format DSD, PCM DSD 2.8M / 5.6M / 11.2MHz PCM 32k / 44.1k / 48k / 88.2k / 96k / 176.4k /192k / 352.8k / 384kHz, 16 / 24 / 32bit Analog Audio Input Connector RCA jack x 1 pair Input Impedance 51k ohms Sensitivity 130mV Analog Audio Output Connectors Balanced XLR 3-32 x 1 pair Unbalanced RCA jack x 1 pair Output Impedance Balanced 188 ohms Unbalanced 150 ohms Max Output Level Fixed (0dB) 2.0Vrms (XLR/RCA) Fixed (+6dB) 4.0Vrms (XLR/RCA) Variable 12.0Vrms (XLR), 6Vrms (RCA) Frequency Response 5Hz to 80kHz (+1dB/–3dB) Signal-to-Noise Ratio Balanced 112dB (A-weighted, 1kHz) Unbalanced 110dB (A-weighted, 1kHz) Total Harmonic Distortion 0.0015% (1kHz, LHF: 20Hz to 20kHz) Headphone Output Connectors 1/4" (6.3mm) Stereo jack x 2 Format Balanced, Active Ground, Unbalanced Polarity Balanced Tip: HOT, Ring: COLD, Shield: GND Active Ground Tip: HOT, Ring: COLD, Shield: GND Unbalanced Tip: L, Ring: R, Shield: GND Max Output Power Balanced 700mW + 700mW (32ohms loaded, THD 1%) Unbalanced 500mW + 500mW (32ohms x 1 loaded, THD 1%) 350mW + 350mW (32ohms x 2 loaded, THD 1%) Supported Headphone Impedance 16 to 600 ohms Audio Settings Up-conversion x8, x4, x2, Off DSD Cut-off Frequency 50kHz, 150kHz PCM Digital Filter FIR Sharp, FIR Slow, Short-delay Sharp, Short-delay Slow Line Output RCA, XLR (Pin2: HOT), XLR (Pin3:HOT) Line Output Level Fixed (0dB), Fixed (+6dB), Variable, Off Supported OS Windows Windows 10 (32/64-bit), Windows 8.1 (32/64-bit), Windows 8 (32/64-bit), Windows 7 (32/64-bit) Macintosh El Capitan (10.11.1), Yosemite（OS X10.10）, Mavericks（OS X10.9）, Mountain Lion（OS X10.8）, Lion（OS X10.7） Operation Power US/Canada AC 120V, 60Hz UK/Europe AC 230V, 50Hz Power Consumption 16 Watts (0.4 Watts at Standby Mode) Overall Dimensions (including protrusions) 11.4" (W) x 3.2" (H) x 9.8" (D) 290 (W) x 81.2 (H) x 248.7 (D) mm Weight 9.3 lbs. / 4.2 kg Accessories Remote control (RC-1319), AAA Batteries x 2, RCA-Mini Plug Cable, Power Cord, Cushion for Foot x 3, Owner's Manual (including Warranty card)|