(10-Sep-2014, 09:11)thumb5 Wrote:

(09-Sep-2014, 13:12)Confused Wrote:

(09-Sep-2014, 12:41)IanG-UK Wrote: Where I differ a bit with "Confused" is his conclusion that the Totaldac clocking ability is superior to AIR. Surely it is just audibly different to two individuals' sets of ears in a way which pleases them!

Actually I would have to stick with a conclusion that the Totaldac may have superior clocking ability. The fact is I have never listened to a Totaldac D1, and hearing is believing for me. However, looking a some of Guillaume's and Rufus' previous posts, it is clear that they think that they are hearing a most definate improvement, i.e. they sound like they are a little beyond the subjective range. As I mentioned, I would need to hear one myself before stating anything more than a tentative "may have".

Please excuse me if I go into pedantic mode for a while. (Maybe that should be a given )

Guillaume and Rufus clearly agree that the Totaldac d1 server sounds better than AIR, and I certainly don't doubt their judgement. But in the absence of measurement that is by definition a subjective judgement. That being the case I don't think one can or should conclude from their comparison that the Totaldac is providing technical (objectively measurable) improvements over AIR, for example in the area of clocking. It may or may not be measurably different but the subjective improvement in sound quality does not necessarily means it's technically better than AIR - "lower jitter", "more bit perfect", however you might interpret those terms.

(09-Sep-2014, 19:58)PhilP Wrote: If clocking is the main reason for the difference in sound between AIR and Totaldac AES/EBU and both mechanisms provide bit-perfect data to the DAC then the implication is that Devialet's buffering and re-clocking of AIR-transported data is sub-optimal. If so, I'm very surprised that Devialet would have made that compromise given that AIR is one of their flagship technologies. And it sounds pretty good to me anyway

(10-Sep-2014, 09:40)thumb5 Wrote: As always, subjective judgements of sound quality can and should continue independent of the technical discussion...

(10-Sep-2014, 09:40)thumb5 Wrote: One key difference between AIR and AES/EBU (as I understand it, please correct me if I'm wrong) is that with AES/EBU, the source (e.g. Totaldac d1) encodes the data stream using its own clock and the Devialet has to extract the clock from the data stream. I'd assume it then has to either drive its own audio playback pipeline completely from the recovered clock, or somehow re-clock/re-sample the data to synchronise it with its own internally-generated clock. For what it's worth, my guess is the latter case. Although the two clocks should of course be nominally running at the same rate, over a long-enough time they will necessarily drift because neither of them can be completely accurate/stable. This clock synchronisation process might introduce subtle changes to the data stream - who knows?

Another factor is that the AES/EBU interface has limited error detection but essentially no mechanism for error correction. These AES/EBU guidelines suggest in section 3.8 that a DAC detecting errors in an AES/EBU input stream should handle them by interpolating between valid samples, or by muting its output. Needless to say, neither of these can be considered "bit perfect" activities. I've also seen this referred to as "error concealment" rather than error correction.

thumb5 Wrote:As always, subjective judgements of sound quality can and should continue independent of the technical discussion...

(10-Sep-2014, 13:56)Confused Wrote: Ian - Perhaps someone should take these queries to the Guilford Audio event in October. (I doubt they will get a sensible answer though)