BRYSTON BDA-I
BDA– I EXT ERNAL DAC
THE EVOLUTION CONTINUES
IntroducIng THE BDA-1 EXTERNAL DAC
BRYSTON BDA-1 EXTERNAL DAC
STATE-OF-THE-ART
The Bryston BDA-1 is a state-of-the-art external
Stereo DAC (digital to analog converter) using fully
discrete Class-A proprietary Bryston analog circuits,
two independent linear power supplies and dual Crystal
CS-4398 DAC chips. The BDA-1 features an impressive
array of inputs for USB, COAX, OPTICAL, AES-EBU
and BNC equipped digital devices. For audio outputs, the
BDA-1 offers both balanced XLR as well as unbalanced
RCA stereo connectors on the rear panel. The BDA-1 is
RS-232 software upgradeable, making it the most flexible
high performance DAC on the market.
• Transformer-coupled SPDIF and AES EBU
digital inputs
• SPDIF COAX bypass loop output
• RS-232 software upgrade
• Optional remote control
• Remote 12-volt trigger
• Compatible with CD drives, sound cards, computers,
music servers
• Cosmetically matches Bryston C-Series BP26/
MPS2/BCD-1
BDA-1 FEATURES:
• Dual 192K/24Bit Crystal DAC’s
• Independent dual power supplies
• Discrete Class A analog output stage
• Oversampling
• Synchronous upsampling (176.4K/192K)
• Selectable upsampling feature
• Independent analog and digital signal paths
• Inputs: USB (1), COAX (2), OPTICAL (2),
AES-EBU (1) BNC (2)
• 32, 44.1, 48, 88.2, 96, 176, 192K sampling
• 16-24Bit PCM, 16Bit 32K-48K USB
• Fully differential balanced XLR and unbalanced
RCA stereo outputs
JITTER REDUCTION
Jitter is a mistiming of data being moved from point A to
point B in any synchronous digital system. Think of jitter
as individual ticks on a clock—however each tick is not
occurring at exact one-second intervals. Some are slightly
less than a second and some are slightly longer, and they
average out so that no actual time is being gained or lost over
a large number of seconds. Jitter is the difference between the
shortest and the longest second, and in digital audio systems
this specification is usually measured in nanoseconds.
Both the frequency and the jitter characteristics of the
system’s digital clock will affect the accuracy of reproduction.
The frequency, if not accurate, can cause the pitch and speed
of the music to change, and in some systems cause drop-outs
if there is no data available.
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THE BRYSTON SOLUTION
Bryston delivers superb sonic performance by re-sampling
and re-clocking the digital input in order to reduce jitter. The
result, a significant reduction in jitter (1/1000 of a nanosecond).
But it isn’t enough to just get the bits right; those bits have to
be converted back into music with the same timing reference
as when the music was first digitized. The input signal of the
BDA-1 is re-clocked and re-sampled to reduce any possibility
of jitter affecting the sound quality. Even the input receiver
and the sample rate converter serve to further reduce jitter.
IMPEDANCE MATCHING TRANSFORMERS
The best way to understand the Bryston BDA-1 External
DAC is to follow the flow of a signal from when it first arrives
at the BDA-1 in digital form to when it leaves to drive an
external analog input. The digital signal first arrives at the
SonIc SupERioRiTy
BDA-1 via either the SPDIF COAX, OPTICAL OR AES
EBU inputs or the USB interface input. These are the standard
digital outputs from a CD Drive, Sound Card, Computer,
Music Server etc. There are 6 digital inputs, which are
easily selected using a front panel switch. This digital signal
contains data at over 1 million bits per second that requires
a bandwidth of 5 to 10 million hertz (cycles per second). At
these high frequencies, it is very important to maintain the
quality of the signal by having the correct termination at the
digital inputs. The BDA-1 provides for this termination in
the best possible manner using devices called impedance
matching transformers. Impedance matching transformers
provide the optimal interface to the incoming source under
all sorts of signal conditions. Lesser quality terminations will
degrade the signal, causing increased jitter.
separate power transformers for separate
analog and digital power supplies.
multi-stage voltage
regulation and filtering
for analog and digital
power supplies
digital input
signal isolation
transformers
dual D/A
convertors
discrete analog
amplifier output
stages
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SYncHronouS upSAMpLiNG
UPSAMPLING
After the input stage, the signal goes to the
SYNCHRONOUS upsampling circuit (sample rate
converter). This circuit converts the digital signal from one
sample rate and bit depth to another. In the BDA-1, the
sample rate is increased from the input sample f requency
(32K, 48K, or 96K upsamples to 192K and 44.1K or
88.2K upsamples to 176.4K). The 16 bits of depth (the
CD standard) is increased to 24 bits. The added 8 bits
are filled with placeholder information. This upsampling
process provides a digital signal for later conversion to analog
by the Crystal 4398 DAC chip. The upsampling process
doesn’t add any new, but does put the data in a form which
can better be translated by the DAC as described below.
The advantage of this synchronous upsampling process is
improved processing of the upsampled signal by the DAC
chip, which was designed for higher sample rates and bit
depths. There is also a noise shaping process implemented
where “noise” within the audible spectrum is shifted up to
frequencies above audible limits. An added advantage of
this upsampling process is that a totally new clock signal is
applied, which results in significant jitter reduction.
OPTIONAL UPSAMPLING FEATURE
A very unique feature of the Bryston BDA-1 External
DAC is the ability to disengage the upsampling feature. You
can compare an upsampled signal with a non-upsampled
signal simply by engaging a switch on the front panel. This
feature is functional when using sample rates of 44.1K,
88.2K, 48K, and 96K.
BRYSTON DAC
The DAC integrated circuit (chip) provides the conversion of
the digital signal to the analog domain. The two independent
DAC chip’s used in the BDA-1 are the Crystal CS-4398. Due
to the requirements of the conversion process, every DAC
chip employs a digital filter to the signal in the digital domain
and an analog filter after the conversion process has been
applied. Without this upsampling technology, these filters
would likely effect frequencies at or near the audible range,
accompanied by unwanted level and phase changes.
The CS-4398 is a hybrid multi-bit delta-sigma DAC. This
is an advanced generation chip, which uses several methods
to optimize the conversion process. This DAC uses a process
similar to the previously detailed upsampling process where
it oversamples the incoming signal. The CS-4398 operates in
one of three oversampling modes based on the input sample
rate. Single-speed mode supports input sample rates up to
50 kHz and uses a 128x oversampling ratio. Double-speed
mode supports input sample rates up to 100 kHz and uses
an oversampling ratio of 64x. Quad-speed mode supports
input sample rates up to 200 kHz and uses an oversampling
ratio of 32x. This again allows for filtering that is safely out
of the audible range. The output of this process is a sensitive
analog signal. The timing of this process must be very closely
controlled by a low-jitter clock.
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OPTIONAL REMOTE
POWER SUPPLY
The stability of power in any audiophile equipment is
imperative to superb performance. The BDA-1 uses two
independent power transformers for the initial stages of
filtering and regulation. In the BDA-1, each stage in the
digital chain (input receiver > sample rate converter > digital
audio converter) is independently regulated to prevent any
interactions and to provide a rock solid supply of power for
any up-sampling/over-sampling process.
The Crystal DAC chip also requires a very clean digital power
supply if it is to function at its optimum level. Noise on the digital
supply could cause added jitter and various forms of distortion.
Incorrect circuit board routing of the digital power supply or
related ground may also introduce digital noise into the analog
circuits. The BDA-1’s digital power supply is provided from a
separate closely regulated and filtered source.
The DAC also requires a high quality analog power source.
The analog signal is at its lowest magnitude within the DAC
and as it exits the chip, so any induced noise or distortion will
be greatly amplified by circuitry upstream from the DAC.
Bryston engineers have employed a separate, heavily regulated
and filtered power supply with carefully routed grounds that
is critical to the superior sound of BDA-1. Careful trace
routing eliminates the risk of noise via capacitive coupling
and provides the extra dB’s of noise and distortion reduction
which separate truly great audio equipment.
DISCRETE CLASS-A ANALOG STAGE
The most critical part of the circuit design in the
Bryston BDA-1 is the DAC’s analog outputs—connected
directly to a pair of proprietary Bryston Class A discrete
operational amplifiers rather than the typical IC chips
employed in most other products. These exotic amplifiers
make a huge difference in transparency, resolution and
dynamic performance.
The use of discrete devices allows the design of a circuit
that exactly matches the needs of the DAC, whereas
the use of general-purpose integrated circuits always
involves compromises. Discrete devices allow engineers
to generate more output power since the heat from the
output driver transistors is physically separated from
other sensitive components.
Discrete devices also allow specific matching of important
characteristics such as input and output impedances based
on the specific in-circuit requirements. Discrete operational
amplifiers can also be designed to more closely match their
power source leading to additional reduced distortion and
noise. Bryston consistently utilizes discrete devices in our
product designs because our circuits are engineered to
require closely matched devices for optimum performance.
Bryston does ultra-fine sorting and grading of discrete
devices, which leads to superior sound quality.
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PErForMAncE WItHout CoMpRoMiSE
HAND ASSEMBLED WITH CARE
Bryston hand assembles and individually tests each
and every product we manufacture. We exclusively use
only the finest components, 1% metal-film resistors, 1%
polystyrene capacitors, and hand selected and matched
transistors in order to reduce noise and distortion to
the absolute minimum. Bryston applies techniques and
employs custom materials in our everyday construction of
electronic equipment that are typically utilized by military
and aerospace industries. Our traditional adherence to the
use of proprietary parts, sophisticated construction, and
refined testing techniques guarantees that the Bryston
BDA-1 DAC will perform superbly for many years.
PERFORMANCE WITHOUT COMPROMISE
Bryston has always maintained that the final arbiter of this
exercise is to provide products that are as transparent and
accurate to the original recorded performance. The BDA-1
DAC is the ultimate representation of this design goal.
SPECIFICATIONS
•Frequencyresponse-20Hz-20KHz-.1dB
•Signaltonoise–AudioPrecisionAP2700analyzer
FFT digital measurement 140 dB unweighted
•THDplusnoise-.002%
•IMD-.002%
•Jitter–belowthemeasurementcapabilityofthe
AP2700 analyzer
• Output Level - 2.3V unbalanced - 4.6V balanced
• Shipping weight - 18 Lbs / 8.2 Kg
• Dimensions - 17 or 19 w / 11.25 d / 1.75 h inches
• 43.2 or 48.3 w / 28.6 d / 4.4 h cm
Bryston Ltd. P.O. Box 2170, 677 Neal Drive, Peterborough,
Ontario Canada K9J 7Y4 1-800-632-8217 bryston.ca
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