Why was it decided not to reclock? Meridian, Anthem, and other competitors all highlight that their products reclock to reduce jitter and Bryston has chosen to re-clock in some of its other products.
With re-clocking in the SP1.7 there is a DSP horsepower issue. We simply cannot implement a reclocking or upsampling algorithm in the current DSP. We don't have a reclocking hardware circuit, because of cost/complexity issues, and they tend to interfere with the decoding of DTS, Dolby Digital etc...
On the SP2, however, we have the capability to implement upsampling which we may do in the future. Make sure you understand the difference between upsampling and reclocking. The Anthem unit that you mention, for example, performs upsampling - NOT reclocking. Upsampling is a relatively easy algorithm to implement if you have the MIPS and helps with aliasing distortion, but does very little to improve jitter (due to the synchronous nature of the operation).
We were, of course, talking about asynchronous
upsampling. From Bryston Newsletter Volume 8 Number 1
, talking about the BP25DA, written by James Tanner, emphasis added by myself:
Up-sampling 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 up-convert mode. So in the BP25 DA, if a 44.1 kHz signal is present: we up-sample to 96kHz (with the Sample Rate Converter) and then the DAC will internally 8x over-sample that signal.
The up-sampling method, when implemented correctly, also has the side effect of jitter reduction, since the output clock is usually asynchronous from the input clock.
So... does all this mean that we definitely will not
ever be able to resample 44.1kHz to 96 kHz on the SP2, and thus benefit from the jitter reduction which is so beneficial to the sound quality of the BP25DA?
And I'm going to keep on asking about this, too
- are there any plans for Dolby Headphone output on the SP2?