I2S

The I2S Audio Interface provides a bidirectional, synchronous, serial interface to off-chip audio devices.

The I2S or Inter-IC Sound Standard was developed by Philips to allow audio
data exchange between converters, filters and digital input/output interfaces.
The serial interface is a three-wire bus that contains a line for two timemultiplexed
data channels (Data), a word select line (L/R clock), and a clock
line (Bit Clock). The standard also dictates that the actual audio data be
delayed by one Bit Clock period from the L/R clock.

 

This is the protocol used inside CD players to connect the drive and the DAC.

It is a true computer protocol:

bidirectional: the devices can communicate with each other

signal (audio) and timing are send as data.

 

Compared with S/PDIF this protocol has the advantage of sending both the timing information and the signal as bits.

 

More: http://www.interfacebus.com/I2S_Interface_Bus.html

 

I2S is used as a protocol between chips on the same board.
Some manufacturers use it to connect  boxes.

As there is no standard for cabling, each does it in his own way.

 

DAC's with I2S input:

 

April music Stello DA100 Signature

North Star Design

PS Audio - PerfectWave DAC

Zero One