The only company that uses I2S over HDMI is PS Audio.
20 responses Add your response
Most I2S is not over HDMI (except as Kr4 pointed out, for PS Audio), but there are several different I2S interfaces. The difference between the I2S and the common s/pdif is that the I2S includes the word clock communication, allowing a DAC to sync with a transport, minimizing jitter.
Coax (s/pdif) is superior to toslink (optical) in almost all applications (due to lower jitter amongst other things). AT&T is superior to s/pdif in most applications...
USB... can be a good interface, but many times, not very well executed. HDMI, potentially a very good interface, but contains all kinds of copy right protection which can screw up the sound...
Given that the system does not have significant ground-loop noise, the coax interface will outperform the Toslink, If you use a decent coax cable that is. The Optical conversions add jitter. If the system has a lot of ground-loop noise, the Toslink will be better simply because it breaks the ground loop.
I2S is the native interface to most D/A chips. Because there is no need to encode the clock and data into a single signal, this makes it superior technically to S/PDIF coax. Termination and handling of the transmission-lines of I2S is non-trivial however and many of the early implementations were not very good. I2S consists of 4 signal lines: MCLK, SDATA, L/RCLK and SCLK (aka BITCLK). The HDMI connector used with the differential version of I2S was chosen by PSAudio and adopted by Wyred 4 Sound and Empirical Audio, who also uses RJ-45. I2S has been used in single ended version with DIN and RJ-45 connectors for about 10 years. The earliest was Audio Alchemy. Differential version has 8 signal lines and ground. Single ended has 4 signal lines and 4 return lines (grounds).
Dunno but it is doable. I wrote a pair of articles many years back (1995-7) about how to do this. They appeared in Audio Amateur which has morphed into AudioXpress. The articles were called "Get on the Bus" parts 1 and 2. While the specific devices referred to are a bit dated, the general principles are the same.
did some extensive testing of the I2S connection when i got my PS Audio PWT/PWD back in 2009. all three listeners easily preferred the I2S connection....and i stress the "easily" part as it was obvious to us. we went on to compare the set-up to higher priced gear and the I2S connection held its own...besting transport/dac combo's that cost considerably more. the same was *not* true when we used rca or xlr with the PWT/PWD.
i walked away thinking I2S was the difference maker when properly implemented/executed. i still believe that today.
just my 2 cents though. your mileage could vary.
Cymbop - Actually you can stream USB output from SB Touch, but it requires a USB converter with Linux driver compatibility. The HiFace2 will work.
If you wanted to reduce jitter from S/PDIF coax or Toslink, this can be done with a reclocker like the Synchro-Mesh. Unfortunately, there are none with I2S outputs .... yet.
Quick update on this. Reassuringly I2s is really catching on. These manufacturers (at least) offer I2S inputs or converters:
Interesting thread. I am currently connecting my Apple TV to my DAC (Cambridge Audio Azur 851 D) via toslink. I was advised that this was a better route than coax.
I'm thinking of replacing the Apple TV with a Bluesound Node 2. Based on the opinions on this thread, it seems coax is a better alternative if ground loop noise is not a factor.