Digital vs Interconnect Cables - Difference?

Excellent elaboration by Kijanki, with which I agree 100%. An important bottom line point in his post is that a "cable that is perfect in one system might work poorly in another."

Marakanetz, any designer of an electronic system (audio or otherwise) who creates a design in which digital signals whose waveforms have any kind of criticality are transmitted through a cable whose impedance match to the connected components is random and arbitrary should be fired and/or sent back to school, IMO.

Which is not to say that it won't work ok in some cases. But why design a potential problem into the system, when it is easily avoided?

Regards,
-- Al

Can someone explain the difference between digital and interconnect cables?

A digital cable is a form of interconnect cable, that is designed to conduct digital signals. Another form of interconnect cable is one that is designed to conduct analog signals. I believe that your question is intended to address the differences between digital interconnect cables and analog interconnect cables.

Both analog and digital interconnect cables can be had in balanced or unbalanced configurations. Balanced cables utilize XLR connectors. Unbalanced cables usually utilize RCA connectors, although BNC connectors (which are superior to RCAs) are used occasionally.

Balanced digital cables have 110 ohm impedances, and are NOT coaxial. Unbalanced digital cables have 75 ohm impedances, and are coaxial.

The impedances of analog interconnects may or may not be specified or well controlled.

As Mofi indicated, any of these cable types will function in both analog and digital applications, as long as the connector types match the connectors on the components that are being connected.

IMO, however, using an analog interconnect to conduct digital signals is poor practice, and stands a good chance of being sonically non-optimal. (In saying that, I'm assuming that the manufacturer does not specifically indicate that the cable is suitable for digital as well as analog applications). Digital signals involve vastly higher frequencies than analog signals, which means that a poor impedance match will degrade waveform quality, which in turn may (depending on many system-dependent variables) degrade sonics.

Using a digital interconnect to conduct analog signals stands a good chance of working well, IMO, but depending on the design of the specific cable MIGHT not work quite as optimally as a similarly priced cable that is intended for analog applications. There are several possible technical reasons for that, depending on the specific design, although I suspect that in most cases the differences, if any, would be minor.

Is digital for connecting CD/SACD transport and DAC?

Yes, that is one application of a digital interconnect cable.

How about the cables between CD player and pre-amp - Interconnect or digital cables? And between pre-amp and power-amp?

Those connections usually involve analog signals. See my comments above.

Regards,
-- Al

05-22-13: Mtruong34
I thought for digital, XLR connectors are for AES/EBU standard and RCA/BNC are for SPDIF, not balanced vs unbalanced?

We are almost saying the same thing.

The electrical form of S/PDIF (as distinguished from its optical form, which of course is a different story altogether) is unbalanced, while AES/EBU is almost always balanced.

The reason I say "almost" in both of the preceding paragraphs is that an unbalanced form of AES/EBU exists. As indicated in this Wikipedia writeup, "the AES-3id standard defines a 75-ohm BNC electrical variant of AES3. This uses the same cabling, patching and infrastructure as analogue or digital video, and is thus common in the broadcast industry."

So it is a bit more precise to distinguish between XLR and RCA/BNC connection of digital audio signals on the basis of balanced vs. unbalanced, rather than AES/EBU vs. S/PDIF, if only one of the two sets of terms is being used, and if the context does not make clear what is being referred to.

The first table in this Wikipedia writeup is also informative.

Regards,
-- Al