What makes a Digital Interconnect

What engineering school did you attend?

Columbia (BSEE); RPI (MSEE). However, my engineering career (now retired) was in defense electronics, not audio.

Best regards,
-- Al

Actually, despite having at least 3 ICs specifically designed for digital , I use a standard IC for carrying the data between transport and DAC. I find it does a better job in MY SYSTEM. I see some of the Digital cables are specified at 110 Ohms instead of 75 and some makers say the 1.5 M is the proper length. Al , I will leave the technical details up to you, my attitude toward them is the same as Charles Lamb's toward matters concerning Space and Time: "Nothing puzzles me more than such questions and yet nothing bothers me less as I never think about them". Seriously, I have tried a variety of dedicated digital ICs as well as standard ones and never found 2 who were indistinguishable. Possibly if I had tried freebies or really cheap ones this would have happened. Unless you want to do some serious research don't worry too much about the specs., just hook it up and see what it sounds like.

Good quote from Charles Lamb, Stan. I'll have to remember that one!

For the op's info, 110 ohm digital cables are typically used with xlr connectors for transmitting balanced aes/ebu digital signals. 75 ohm cables are typically used for unbalanced spdif digital signals, via rca or bnc connectors.

In the case of digital or other high speed signals, it IS important that cable impedance match the output impedance of the transport or other source, and the input impedance of the dac or other load. Otherwise increased jitter or even mis-clocking and data corruption can result.

Good point about 1.5 meters (and not less) being the optimal length. The reasons are explained here: http://www.positive-feedback.com/Issue14/spdif.htm.

The importance of all of this is, of course, highly dependent on the jitter rejection capabilities of the particular dac design. There are several unquantifiable variables that enter into the picture as well, including the risetime and falltime of the output signal of the particular transport; the ambient electrical noise environment; ground offsets between the two components; the value of the logic threshold for the digital receiver chip at the input of the dac; the clock rate of the data (redbook or high res), etc. So Stan is right -- give it a try, and if possible compare with a few other cables in your particular system.

Best regards,
-- Al

Almarg

Al wrote
Columbia (BSEE); RPI (MSEE). However, my engineering career (now retired) was in defense electronics, not audio.

For a moment there I felt quite safe... knowing I was out and you were in.... then I read the retired part.

I'm feeling less secure Now.

I posed my OP to the manufacturer. Here's the response edited to anonymise, the cable in the OP is X:

"The X is an excellent digital cable, the Y is the digital version, and essentially just has more shielding. Both are 75 Ohm cables, with killer bandwidth and excellent group delay. If you are using X [instead of] Y, I would save your cash, spend it on music instead. "

Here are the specs on the dedicated digital cable "Y":

3.3’(1.0m) [RCA > RCA]
Geometry: coax
Bandwidth: > DC - 1 GHz | Linear Phase
Cp: 65 pF (pin / ground)
Ls: center pin 2.6 μH
ground 0.5 μH
Bend Radius: 3.5” (90mm)
Cable Diameter: 0.35” (4.8mm)
Shielding: Shielding shunted to ground at both ends of cable