DACs

Bryston BDA-2 DAC

ARTICLE INDEX

The Design

Compared to the BDA-1, the BDA-2 uses 32 bit DACs (AKM). Over the past couple of years, I have seen manufacturers who produce digital components moving towards the 32 bit arena. Of course, there are no 32 bit music or movie sound tracks, but 32 bits gives the DAC some headroom so that no bits are truncated during processing. In other words, you get the full benefit of the current 24 bit sound, and 16 bit music is a breeze.

The DAC is balanced circuitry, having a stereo DAC for each of the outputs, with one channel of the stereo DAC being used for the + side of the signal, and the other channel for the - side. This is for the XLR analog balanced output. If you use the RCA analog output, only one channel of the DAC is used for each of the two RCA output jacks. In general, balanced circuitry is a good thing to have, since you get common mode rejection of any electrical interference that gets into the circuit, and also because there is twice the voltage output, which means lower overall noise, since the voltage is higher than the noise floor.

The front panel has indicators for the bitstream word depth and sampling frequency, e.g., 44.1, 48, 88.2, 96, 176.4, and 192 kHz. The input is selected by pressing one of the eight buttons on the right hand side, with the power on/off button to the far right. The eight inputs include two Toslink optical, two S/PDIF BNC, two S/PDIF RCA, one XLR, and USB. Lastly, there is a button to turn on upsampling, which allows for a more shallow slope in the cutoff filter.

Bryston explains the technology behind the BDA-2:

"The main motivation for the BDA-2 was to improve the USB input to allow for asynchronous USB and up to 192/24 bit high resolution playback.  Asynchronous decoding uses the high quality high precision digital clock in the BDA-2 rather than utilizing the clock in the source computer. Timing is critical in a DAC to reduce jitter (timing) errors in the digital bitstream.

"We evaluated a number of DAC’s and chose the AKM 4399 due to its sonic qualities, excellent measured performance and potential for DSD decoding (software required).  

"Most quality DAC chips perform well so what makes the BDA-2 unique in the market is the serious attention paid to many other parameters such as independent power supplies for the digital and analog sections, fully discrete Bryston proprietary analog circuitry, transformer coupled digital inputs, circuit board trace routing, independent circuit board traces for the analog and digital sections, grounding optimization for improved noise floors, proprietary part selection, multiple digital inputs (8 total) etc.

"The result is a DAC that in our opinion measures and performs at a state of the art level at a very reasonable price."

The rear panel is shown below.

From the left are two XLR analog outputs, two RCA unbalanced analog outputs, a S/PDIF output (if you want to have the digital signal pass through to another component), a USB-2 input, one XLR balanced input, two BNC S/PDIF inputs, and two RCA S/PDIF inputs. There is also a trigger connector for automatically turning on the DAC when you turn on your transport (if the transport has a trigger output). The RS-232 port is for updating firmware. There is a grounded AC receptacle at the far right.