A Superior DAC Approach
Add a DAC to your compatible Bryston preamp or integrated amp, and enjoy the superior sound quality of Bryston's digital circuitry.
"The sound makes it a stunning value," reports Audio Ideas Guide. "Having the DAC built right in also takes one interconnect cable out of the equation, further increasing the chances of a sonic improvement in your system."
For its internal DAC, Bryston uses a hybrid multi-bit delta sigma DAC device. Before the digital data reaches the delta-sigma modulator, it is run through an 8x over-sampling process and digital interpolation filter. Due to the inherent over-sampling process of a delta-sigma modulator architecture, the overall interpolation ratio of the device is 128 times. Oversampling and upsampling have some great benefits when implemented correctly.
Upsampling Vs. Oversampling
There is a significant difference between upsampling and oversampling. Oversampling is when the samples are repeated (2x, 4x, 8x, etc.) to create a new sampling frequency. The new samples are then generally run through an interpolation filter to create a more analog-like waveform.
Upsampling usually refers to a mathematical process in which the new sample rate is not a multiple of the old sample rate, and the numbers have to be calculated in real-time. This is what is happening when a sample rate converter chip is in an upconvert mode.
Relaxing the Requirement of the Analog Filter
So in the BP-26 DA, if a 44.1 kHz signal is present, it upsamples to 96 kHz (with the Sample Rate Converter) and then the DAC will internally 8x over-sample that signal. The great benefit of both of these methods is that it relaxes the requirements of the analog filter after the DAC.
This is important because it allows designers to implement higher cutoff frequencies with slower roll-offs, which results in a phase linear circuit in the audio band.
The upsampling method, when implemented correctly, also has the side effect of jitter reduction, since the output clock is usually asynchronous from the input clock. Another thing to note is that if the oversampling or upsampling processes are implemented poorly, they can actually introduce jitter. This is usually a result of poor power supply implementation.
So, in the Bryston DAC, each stage in the digital chain (input receiver > sample rate converter > digital audio converter) is independently regulated to prevent any interactions and to provide rock solid power supplies for any upsampling / oversampling process.
The Bryston Difference
All of this being said the most critical part of the DAC circuit in the Bryston Preamplifiers and Bryston Integrated Amplifiers is that the output from the D to A is directly connected to a pair of Bryston proprietary Class A Discrete Operational Amplifiers rather than the typical IC chips employed in most other products. This makes a huge difference in resolution and dynamic headroom performance.
The BP-26 DA can be ordered with the following Bryston components: BP 6 Preamplifiers, BP 16 Preamplifiers, BP 26 Preamplifiers, B 60 Integrated Amplifier, and B100 Integrated Amplifier.