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.
