Originally Posted by Graz
given this topology, I don't think I'd enjoy much benefit with this device over my existing setup...
I don't think that's the right conclusion. If the jitter rejection of the ASRC is good and the device is well-implemented, this would be a very good device. The combination of PLL+ASRC is an "over-engineered" solution for eliminating jitter. Over-engineering is usually good.
|Wodgy, your assertion about keeping S/PDIF in the equation is interesting to me. I've made a couple of inquiries at diyaudio.com on this topic & several folks over there were telling me to skip S/PDIF altogether & stick with TTL (I2S) if at all possible.
The problem with diyAudio is that many of the more vocal guys have a poor grasp of what they're talking about, and the knowledgeable guys are often silent.
The only challenge in designing a DAC is getting the timing right (eliminating jitter) -- in a decent design there are no data errors. If you take an I2S signal and feed it into a DAC, you're depending on the clocking information in that signal to be correct. Where does that clock come from? The receiver reconstructs the clock as data is incoming, then squirts it out as part of the I2S signal, so the quality of the clock is entirely dependent on the quality of the receiver. This is no different from how an S/PDIF receiver operates. (In fact, the Burr-Brown USB receivers use the same algorithm (SpAct) for reconstructing the timing as the Burr-Brown S/PDIF receivers.) You might as well feed this signal through as many jitter filter stages as you can, which is why passing the signal to the AKM S/PDIF receiver in the Perreaux design makes sense.
By the way, the "I2S solves everything" myth is being fanned by a pair of commercial vendors: Wavelength Audio and Empirical Audio. The former guy is a decent tube amp designer but has a poor understanding of digital circuits. The Empirical Audio guy on the other hand is borderline dishonest. It's not even clear his mods use an I2S connection. It's my belief that his mods use a TTL S/PDIF connection (but I'm open to being proved wrong). Nothing wrong with this, but some people seem to believe they're getting something else. Incidentally, he's also the guy who's been pushing the bizarre "digital cables need to be at least 1.5m long" mantra. Apparently no one has told the digital broadcasting/high speed data transmission community.