Best Cable Option: Streamer to DAC

S/PDIF is also limited to 24 bits while USB can pass 32 bits (in case you are interested).

Is there an audible difference? Now that’s a loaded question!

My feeling is that, all things being equal, yes there is an audible difference.

I’m a big proponent of using a DDC when passing hi-res files (DSD) through USB to a DAC. I connect my media player to a DDC (Singxer SU-1) then on to my DAC (Gustard x20 Pro) via I2S. 
My media player is an Asus VivoPC (a fan-less, small form factor pc) so to remove all noise from the USB, I rely on the DDC. At lower resolutions it may not make a noticeable difference though.

It’s a very good question.  Unfortunately, the answer isn’t  nearly as good: It depends.

It depends on your particular components.  In newer units, and only in general, it would appear to most forum participants that USB tends to sound better than SPDIF (and AES EBU which is essentially an SPDIF over a balanced cable) as it is higher bandwidth and enables the DAC to be the clock coordinating the two.  There are those who disagree, of course.  And, many successfully argue that USB is a terrible audio interface as it’s really optimized for computer convenience.  It can pick up electrical noise and be finicky.

Nevertheless, in my own units, USB is superior to SPDIF.   It’s pretty clear that there are very good older DACs for which the USB interface was an afterthought and falls far short of SPDIF.  If you use SPDIF, be sure to use a 1.5M true digital cable with a 75 ohm impedance. (Worth some google time as to why if you’re wanting to use and SPDIF).

Optical solves an electrical noise problem but it tends to be “jittery” and I haven’t seen many people claiming it’s the equal of USB or SPDIF.

Some new units also accept Ethernet and some are using IS2. I am using the latter between my Auralic Aries G2 and Auralic Vega G2.1. It’s at least the equal of the USB (probably slightly better) but also allows additional communication and resource sharing.  

In sum, the only way to really know is to try the various options with your own gear.  You may conclude something entirely different than what I’ve suggested above, or you may find that your results are somewhat consistent with the above.  Unfortunately, there’s no substitute for trying it yourself.  But, i do think your DAC manufacturer will have some guidance as to what they suggest will work best.  Perhaps start there.

Best,

The best (as always) is what sounds best to you in your budget.

Nyquist applies only to continuous waves, so intermittent (music) 22kHz signal would have sidebands that may encroach on the 1/2 sampling frequency limit. It is remotely possible, but amplitudes of folded signals will be extremely small (as are 22kHz harmonics). 96kHz sampling would fix it for sure, but some people claim they need 192kHz. Same goes for number of bits. 16 bits means about 96dB dynamic range requiring 96dB of system total S/N to hear it. 24dB provides about 144dB dynamic range. In order to hear lowest bits you need 144dB S/N. Nobody has that, but you want 32 bits (192dB), claiming it sounds better?
On one hand it is insanity, but on the other - if it helps (placebo effect) it helps, and there is nothing wrong with it. ;)
Other than injected noise (computer cable is connected) asyn USB should be better, since it delivers only data (timing is not involved). S/Pdif has timing encoded with data and that can produce timing jitter (DAC clock is based on it). There are many factors involved in selecting best interface (Ethernet, USB, Toslink, Coax) and nobody can know for sure what is the best solution in your home. Trying at home and comparing seems to be the best course of action.

"Jitter is no longer an issue with most modern DAC’s or streamers that now has internal clocks to combat jitter."

This is totally incorrect as virtually any DAC will provide better SQ if it is fed a cleaner digital signal.

There are many fine renderers or digital bridges that will aid in providing a better digital stream to the DAC than the one coming out of a PC, for example. Some of them terminate with a s/pdif, some with USB and others with I2S. Users have found quality sound with each of these types. The price ranges for these are quite large. Some of the highest value devices use s/pdif as output.

My DAC will accept an I2S input and, theoretically, it should be best. But I did some research on the issue to find, to my satisfaction, that any such device at a reasonable price did not perform as well as the unit I finally ended up with that has a USB output.