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The Bryston BCD-1 is a State-of-the-Art Redbook CD player using
fully discrete analog Class-A proprietary Bryston circuits, a quality
Drive, and a 192K/24Bit Crystal DAC.
The advantage of an all in one box solution for a CD Player (as
opposed to a separate outboard DAC and Drive) is the elimination
of jitter. For optimum performance the Drive and DAC must use the
same MASTER CLOCK. If the clock signal of the drive is not synchronized
with the clock signal from the DAC then jitter develops. In external
DACs the digital input must be re-clocked in order to reduce the
jitter. Jitter is defined as mistiming of the digital signal. The
timing of all those ones and zeros is of extreme importance. It
isn’t enough to 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. These timing errors (jitter) are the bane of
quality audio. With the Bryston CD player the master clock and the
drive are synchronized perfectly to eliminate any possibility of
jitter affecting the sound quality of the player.
The DAC integrated circuit (chip) provides the conversion of the
digital signal to the analog domain. The chip used in the BCD-1
CD Player is a Crystal CS4398. The CS4398 is a hybrid multi-bit
delta-sigma DAC. This is a rather tongue-twisting description that
refers to an advanced generation chip using a combination of several
different methods to optimize the conversion process. This DAC uses
a process to over-sample the digital input 128 times.
Over-sampling is when the samples are re-read (2x, 4x, 8x, etc.)
to create a new sampling frequency. The new samples are then run
through an interpolation filter to create a more analog-like waveform.
The output of this process is a very sensitive analog signal and
it is critical that the timing of this process is very closely controlled
by a low jitter clock.
DAC chips also require a very clean digital power supply if they
are to function at their optimum. Noise on the digital supply may
cause added jitter, noise, and distortion. Incorrect circuit trace
routing of the digital power supply or ground may introduce digital
noise into the analog circuits. This digital power supply is provided
from a separate closely regulated and filtered source. The DAC also
requires a high quality analog power source because the analog signal
is at its lowest magnitude when it enters and leaves the DAC. As
a result, any added noise or distortion will be greatly amplified
by later stages. Again a separate, heavily regulated and filtered
power supply with carefully routed grounds is provided. Finally,
if a digital trace, signal or power, is routed in a layer above
or below an analog trace it can induce noise via capacitive coupling.
Careful trace routing eliminates these problems and provides the
extra dB’s of noise and distortion reduction which separates
good from outstanding equipment. This attention to detail with the
power supplies is one of the reasons for the superior sound of the
BCD-1 Bryston CD Player.
Getting the Digital side of the equation correct is only the start.
Once the signal leaves the DAC it is buffered and increased in strength
by operational amplifiers. In the Bryston BCD-1 CD Player these
are constructed from discrete devices (individual transistors, resistors,
and capacitors) instead of the commonly used integrated circuits.
The use of discrete devices allows the design of a circuit that
exactly matches the needs of the DAC. The use of integrated circuits
always involves compromises since they are designed as general-purpose
devices. Discrete devices also allow for more powerful outputs from
operational amplifiers since the heat from the output driver transistors
is separated from other devices. In an integrated circuit op amp
this heat can affect the rest of the circuitry since it is all on
one chip.
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. Discrete devices can be tested very closely
to meet specific tolerances and can be matched against each other
when a desired performance design is critical. Circuits can be and
are designed to require closely matched devices for optimum performance.
Integrated circuits have large numbers of components on one chip
and it is not practical to do more than high-level sorting of device
characteristics. Bryston does sorting and grading with its DAC chips
but does so to a much finer level with the discrete devices, which
leads to superior sound quality.
Bryston hand assembles and individually tests each and every product
we manufacture. We exclusively use only the finest components in
our products, such as 1% metal-film resistors, 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 more typically utilized by military and aerospace
industries. Our traditional adherence to the use of proprietary
parts, sophisticated construction, and refined testing techniques,
guarantees that your Bryston CD Player will perform superbly, without
any problems, for many, many years. It also prevents any unit-to-unit
variance which inevitably is the result of any mass produced product.
With today’s increased clarity and dynamic range in recordings
you need equipment that not only equals but surpasses the parameters
of the most demanding material available. The Bryston BCD-1 CD Player
is without peer in meeting this performance challenge.
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