Do I need an expensive digital cable?

@rbstehno 

The better sounding transports use i2s to the preamp

You have picked the one digital link where the cable should really matter. I2S was never designed to be transmitted over a cable.

As a workaround, often an HDMI connection is drafted in for use by I2S, on the proviso that the cable length be kept as short as possible, under say 0.5m.

Digital works repeatedly and reliably because errors in transmission can be detected and corrected if decent protocols are used.  I2S by design does neither.

"Can anyone make a case that I should buy a "better" coax cable?"

Terms like better and expensive really don't mean much in this context, but I understand what you're asking. You can get a cable that sounds different than the one you currently have, but you have to be the one that makes the call on better sound. I found this in one of your other responses. 

"I was in the computer industry for years and even though I was in sales, I had to take a number of classes on various aspects of computing. Networking was one of them. I think that networking is done in packets. The transport sends a digital signal from its "digital out" optical and SPDIF cables. It sends an analogue signal through its RCA interconnects. Two different kinds of signals. "

A transport doesn't really send out a digital signal. It's actually an analog representation of the digital signal. Because of that, the signal can be affected by the same things that effects other types of analog signals in your audio system. Your last 2 sentences are confusing. It sounds like you may already know exactly what I just said, or do you mean the analog signal that comes out of a DAC? Most CD players can be used as a DAC or transport, that's why I'm asking. 

Either way, yes, a new cable can make a difference. However, you never really know what the difference will be, if any, so I would always try a new cable first. If you can, try more than one because they all sound different.  

@052rc 

My CD player has a digital out capacity with optical and coax. I assume good old Steve McCormack anticipated that DACs would get better and the UDP-1 owner might choose to run it through a newer more sophicticated DAC. The CD player sends out a 44.1 kHz signal, standard Red Book CD. What networking protocol I have no idea, though. 

The McCormack UDP-1 also has analogue out, of course. I use that, too, because it's a multi-disc player and my Moon 280D will not recognize SACD or DVDA or any higher resolution signal unless it comes from Qobuz, Tidal, or another streaming app. I send the analogue out signal directly  to my preamp and I can play my SACDs and DVDAs through analogue out.

@052rc 

A transport doesn't really send out a digital signal. It's actually an analog representation of the digital signal. Because of that, the signal can be affected by the same things that effects other types of analog signals in your audio system

That is disingenuous.  It leaves out what makes digital special compared with analogue, namely the ability to 'square off" the analogue and to treat the result as an integer number.  Numbers can have error detection added, and protocols can correct errors.  Redbook CDs can correct 4,000 consecutive bit errors.  That's why no matter how often you copy a digital file, you either get an exact replica or an error.  Degraded digital signals don't sound at all like analogue distortions.  If you don't like the sound, and describe the changes in analogue terms, something is getting into the analogue part of your playback chain.

Or you have a digital link which is not error corrected, or simply drops information. That's the original meaning of streaming.

@richardbrand 

I am not an expert on networking or digital signals. Althgouh, I have read articles about both. Here is my simple understanding of digital versus analogue.

A digital signal reproduces a sound wave. I have seen this described on an X/Y axis where each packet of information creates a dot on the X/Y axis and all of those dots eventually create a reproduction of a sound wave. Timing is another story, and to be quite honest, I have never been able to retain exactly how that works. But I know it's important and that a DAC needs a clock. dCS sells an atomic clock for a mere $12,000. An inherent problem with digital is that no matter how how high the resolution (how many dots per inch, let's say) there can never be an infinite number of dots. So, some interpolation will have to be done. I believe that's handled by software that can make a big difference. 

An analogue signal on a record is, in essence, sound waves themselves. If you want to prove this, take an old record you don't care about for an experiment. Make a  paper cone and put a needle through the narrow end of the paper cone. Spin the record with the needle in it and the cone will make music. I think this was how the first Gramaphones worked.

There are so many variables, however. Some records are recorded so badly, you might as well listen to a CD. Artists like Diana Krall make wonderful CDs, in regards to how they sound. Then there is the very high rsolution streaming sometimes offers, 192 kHz (samples per second) sent in a 24 bit word length which is enormous. Red Book CD is recorded at 44.1 kHz (samples per second) with a 16 bit word length. 

Most albums recorded after 1980 come from a digitized source. Stored in the highest resolution files. They sound very good, but on a decent rig like mine, I can tell when records come from a digital source and an analogue source. As I've said, I listen to music while I write. Every now and then I'll hop over to chatgbt and ask, "Does this album come from a digitized source?" And I pretty much am right all the time.