I2S, S/PDIF, Toslink connections

That's 2. Not as many as the original I2S and not standard HDMI either so that's a consideration.

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

I2S is also available on North Star as RJ-45, which I am using.
It certainly is the best connection.

I wish to thank all for their response. Are there no USB/SPDIF converters that output I2S to any of the aforementioned DACS?

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.