Sobremuestreo

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 frequency (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.

Característica de sobremuestreo opcional

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.

DAC Bryston

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.

Fuente de alimentación

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.

Etapa de salida analógica discreta en clase A

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.

Ensamblado a mano

Bryston ensambla a mano y prueba individualmente todos los productos que fabrica. Emplea única y exclusivamente los mejores componentes en sus amplificadores, tales como resistencias de película de 1%, condensadores de poliestireno de 0,1% y transistores escogidos y emparejados a mano, con el fin de reducir el ruido y distorsión al mínimo posible. Su tradicional predilección por componentes a medida, construcción sofisticada y técnicas de control de calidad garantiza que los amplificadores operarán durante muchos años sin problemas.

Prestaciones sin compromisos

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.

Características:

• 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
• 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

Especificaciones: