Looking for a Giant Killer Digital cable

S/PDIF TOSLINK fiberoptic is actually a very horrible cable. The reason is that the LED or light generating source just cannot light up fast enough to transmit the digital square waves properly. It comes across as a very squirly looking wave (not square at all). The result is lost resolution and information - possible problems from signal reflections, ability for target to properly read in the light signals, etc.

Regular S/PDIF COAX digital cable is actually not a bad system, though using BNC connectors is best. Only a true i2s digital connection is better because the DAC/source does not have to encode the stereo digital signals into a single wire signal. That is the S/PDIF method.

Keep in mind that i2s connections will typically use an HDMI cable. This does not mean it’s an HDMI interface. It just uses the cable/connectors as the physical medium for transmitting the i2s signals (which are completely different from normal HDMI audio/video).

if we assume you cannot get a true 75ohm out of an RCA ... I wonder why more manufacturers don't get it right, maybe as those that care that much are including S/PDIF on RCA as a convenience and prefer you use AES3 or some other method?

Simple.  They don't have the expertise/experience to execute these designs correctly.  After seeing many of these designs in my modding days, I came to the conclusion that they just copy each other, not really understanding how the interface really behaves.  The bad designs just get replicated over and over.

Steve N.

Empirical Audio

Regular S/PDIF COAX digital cable is actually not a bad system, though using BNC connectors is best. Only a true i2s digital connection is better because the DAC/source does not have to encode the stereo digital signals into a single wire signal. That is the S/PDIF method.

Keep in mind that i2s connections will typically use an HDMI cable. This does not mean it’s an HDMI interface. It just uses the cable/connectors as the physical medium for transmitting the i2s signals (which are completely different from normal HDMI audio/video).

I2S is not necessarily a panacea either, although its a good start.

Most of my products have I2S interfaces, both SE and differential (HDMI connector), so I know how they behave.

Galvanic isolation of I2S is a non-starter because it adds too much jitter. Because S/PDIF is a zero-crossing signal, at least it’s easy to add a high-quality pulse transformer and get isolation.

I have compare with my own DAC the difference between S/PDIF input (on BNC) to I2S input (on RJ-45). The difference is actually really small, almost audibly undetectable. This is partly because I use a AK4114 receiver, which reduces S/PDIF jitter significantly.

As for differential I2S, the problem there IMO is the LVDS driver and receiver that add jitter. I think the SE I2S on RJ-45 is better.

The other advantage of S/PDIF over I2S is that a world-class cable for SPDIF is a lot less expensive than a world-class cable for I2S.

Steve N.

Empirical Audio