Digital vs Interconnect Cables - Difference?

You can use any analog (RCA or XLR) cable in the place of any digital (RCA or XLR) cable and vice versa.

Digital cables are usually just one cable, so you would need two of them for an analog connection.

XLR connectors would need to be the correct pinout, (most are the same).

I have done this many times. It might not be the correct/proper impedance match, but it sure won't hurt anything.

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

After Al's eloquent posting above, I wanted to clarify my comment.

Can you use an analog cable for a digital cable and a digital cable for an analog cable? Yes, you can, (assuming the connectors are the same). Should you, no probably not, but in a pinch, no harm will be done...other than perhaps a sonic degradation of the signal.

You should always use the proper cable for the application.

I'd like to expand a little on Al's excellent (as usual) post. Each cable has characteristic impedance. This impedance depends on cable geometry and dielectric and can be simplified as SQRT(L/C). When this impedance is different from the gear impedance, that cable is connected to, we will get transition echo from point of impedance change back to the output. Severity of this echo is dependent on the amount of impedance mismatch and slew rate of transitions in digital signal. This echo might reflect many times inside of the cable colliding with original or next transition. This collision will change the shape of transition from smooth swing to jagged one. Jaggies in transition will effect moment in time when logic level change is recognized at certain threshold voltage, resulting in time jitter that D/A converts to noise. Slow transitions would help to reduce this effect but will make system more susceptible to similar jaggies induced by noise that is either picked up by the cable or exists in the gear itself. Very fast change will reduce effect of transition jaggies (shorter time=shorter time variation) but will require better match of cable and gear impedance. 75ohm and 110ohms are standards agreed upon so that we know what we're matching to, but it could be any number. Cable might have 85ohm and it is fine as long as gear happens to have also 85ohm. That's why it is all system dependent. Cable that is perfect in one system might work poorly in another.

Let me try to explain jitter. Imagine sinewave created by series of many equally spaced dots (each dot corresponds to one D/A conversion) - like dotted line. Connecting dots together will result in smooth sinewave - that's what filter does. Now make time distance between dots different (alternate shorter-longer) and repeat connecting dots (keep each dot's amplitude - move in time horizontally). Sinewave will become less smooth. It will have jaggies, like if another frequency is on the top of it. That's what jitter does on analog side. It creates additional frequencies of very small amplitude. With music (a lot of frequencies) jitter will create a lot of additional unwanted frequencies - a noise that is only present when music is present. It shows as a lack of clarity. If you look at this sinewave again you'll agree that size of the jaggies will grow with amplitude of original sinewave. Jitter induced noise is proportional to loudness/level of the music. Digital is not only 0s and 1s but also their moment of arrival, unless music is transferred without timing as data (hard disk, WiFi, Ethernet etc.) Eventually timing has to be recreated for D/A conversion introducing possibility of jitter.
A/D conversion also suffers from the jitter. Artifacts become embedded in digital file and cannot be removed. Many original recordings were digitized poorly with unstable clock and the only option is to do it again if analog tapes still exist.

whoever tells that you can't use analogue cable for digital signal indeed never had tried that.