Do I need an expensive digital cable?

@retiredaudioguy 

My virtual system is so virtual I have not recorded it here .  I suppose I should, because it is very different from usual North American practice!

In my real main system, my DAC function is provided by a Marantz AV8802 pre-processor which contains eight 2-channel AKM dacs.  These natively process Direct Stream Digital (DSD) for a total of 16-channels.  Of these, I use nine when supported by the source, such as immersive disks from 2L - the Nordic Sound.  (Not available from Presto ).

My HDMI cables are only used for HDMI  in accordance with their design goals. 

I know this will be controversial, but I see no point in using IIS (I2S) over any sort of cable, except to avoid HDMI licence fees.  The HDMI fee structure does favour big manufacturers, so I can understand why small manufacturers look for alternatives.  But I2S was designed to connect two chips on a circuit board, and the clock signal attenuates and smears when sent over a cable.

I always listen to SACD (mainly classical) in multi-channel mode, unless it is a rare 2-channel disk.  Same for Pure Audio Blu-ray.  I don't think streaming has got there yet.

In my opinion, there is no point comparing DSD and PCM in terms of equivalent bits and rates - they use bits completely differently.  I don't think any dac handling PCM actually gets close to 24-bit resolution.  DSD is much simpler for dacs to implement.

Having said that, I know many classical SACDs are recorded in high resolution PCM for easy of editing before being converted to DSD for delivery.

Caveat:  None of my comments apply to pop/rock multi-miked recordings where mixing is performed post-performance.

It depends!

If you have an external clock - that cable matters - a lot.  This clock controls the timing of the internal d to a conversion process, so any jitter affects SQ.  That cable is the most expensive one in the digital part of my system.

If you are using I2S - over an HDMI cable or RJ45 - it matters a lot, once again timing data is being transmitted over the cable.

If you are using Toslink - stop (except possibly to hook up your TV).

If you are using S/PDIF Coax - possibly.  The cable must be "decent" - 75 ohm, shielded.  Then it depends on the implementation of the S/PDIF in your DAC.  If the DAC implements a good buffer, isolation and reclocking, then an OK cable will sound as good as a superb one.  In "olden days" then the cable was critical as the DAC's clock was derived from the input data stream.  If your DAC still does this then the cable matters a lot.

With USB - the cable needs to be good enough that the received data is correct, jitter is probably irrelevant as the data presented to the actual d to a conversion has been buffered and timing is solely dependent on the DACs clock.

But then there is the electrical noise that might be picked up by the cable.  Then it depends on how well the interface was implemented, does it provide isolation so that electrical noise does not affect the DAC, unless the noise level is comparable to the signal level which could change the data?  If there is any weakness in that aspect then the shielding or filtering of the cable matters.

My DAC is the Esoteric K-01XDSE wherein the engineers went to extreme lengths to isolate the d to a conversion process from the effects of jitter and noise on the input; I tried switching the Cardas USB cable for one that had come with a printer and could detect no change in any aspect of SQ given intense critical listening.  In my layout the cable is in a pretty benign electrical environment, well separated from power leads etc. YMMV.

I’m going to make a coax SPDIF cable suggestion that’s really quite terrific- Canare CV-77S terminated with Canare crimp on 75 ohm RCAs or BNC. Every bit as good as an Audioquest Carbon SPDIF coax I had in my system for a couple of years. 

^^^
 I wonder if this Canare CV-77S above is the same as Canare LV-77S used by Blue Jeans cables, which they “terminate with Canare crimp connectors”?

https://www.bluejeanscable.com/store/shopbycable/LV77S.htm?srsltid=AfmBOoq3wogsmVCvaqlHsAH2Oj_nqnraWfHeIqA-zFZG0JPDSxFHRY78

@richardbrand 

I don't have an HDMI choice, so I have no idea about it being better. I have, however, been experimenting with DSD vs PCM by playing the same album on Qobuz and Tidal. I think I mostly prefer PCM for its better delineation of instruments. It also handles attacks better. However, every now and then DSD seems more airy and I prefer that on a few albums. My accountant wife says one has to go. I think I'll keep Qobuz.