I2S, S/PDIF, Toslink connections

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).

Steve N.
Empirical Audio

Mesch- the Empirical Audio Off-Ramp 5 outputs both differential HDMI I2S and single-ended RJ-45 I2S. it works with W4S DAC2, PS Audio PWD, Northstar, Stello, Empirical Audio, Perpetual Technologies, Buffalo and others.

Steve N.
Empirical Audio

Cymbop - It has Coax. The OR5 has BNC coax (with RCA adapter), AES/EBU, RJ-45 I2S and HDMI differential I2S. All active at once.

The OR5 USB interface does not currently support Linux without a special driver. OR6 will be XMOS, so it will work. OR5 is upgradable.

Steve N.
Empirical Audio

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.

Steve N.
Empirical Audio