Difference between interconnects and digital cables?

dayneger · « **on:** 27 Jan 2005, 07:52 pm »

I was listening to my system last night when it suddenly occurred to me that, after all these years, I don't really know what the difference is between digital cables and interconnects.

Anyone care to comment?

Thanks!

Dayne

corwin99 · « **Reply #1 on:** 27 Jan 2005, 07:56 pm »

There really isn't a whole lot of difference between a digital coax cable and an interconnect. I prefer to use a 75ohm cable for the digital coax, and i also prefer to use a coaxial configuration cable for the coax as opposed to a twisted pair or twisted quad or litz braid etc etc. Other configurations are likely not 75ohm cables.

Tonto Yoder · « **Reply #2 on:** 27 Jan 2005, 08:53 pm »

Isn't a digital cable most like a video interconnect (rather than an audio one [assuming that the manufacturer actually makes the video cable different rather than just coloring it yellow])?? As corwin mentioned, I believe the 75 ohm rating is what's important with both dig & vid.

corwin99 · « **Reply #3 on:** 27 Jan 2005, 09:27 pm »

yes, the composite video interconnects are often the same as digital cables since both perform optimally at 75ohm. Actually if you look at the packages for monster cables and acoustic research and some other big box cables often the video and digital cables will be identical...

With those cheap plastic RCA cables the include with DVD players etc i dont think they use true 75ohm cables..

Some people prefer 110ohm cables for coax, but as far as i know it is used typically for AES-EBU

dayneger · « **Reply #4 on:** 28 Jan 2005, 07:25 am »

Thanks for the feedbacks!

So does a digital/video cable actually act like a 75 ohm resistor instead of like a wire with a fraction of an ohm resistance, which I'm assuming is how normal interconnects measure?

viggen · « **Reply #5 on:** 28 Jan 2005, 08:16 am »

I think the same rules apply to what makes a good cable regardless of it being used for analog, digital or power. Digital is just somehow said to be best at 75ohm impedance.

ctviggen · « **Reply #6 on:** 28 Jan 2005, 02:09 pm »

The impedance of a transmission line (the cable) should match the impedance of the transmitter (the digital source) in order to lessen losses and reduce reflections. If you were to look at the actual signal on an oscilloscope, if you had perfect impedance matching, you'd have a very crisp signal. If you have poor impedance matching, a larger reflected power would occur, which will mess up the signal.

corwin99 · « **Reply #7 on:** 28 Jan 2005, 03:28 pm »

A 75ohm characteristic impedance cable does not act like a 75ohm resistor.... this not quite the same as resistance. The Characteristic impedance of a cable is determined by several factors including the size of the conductors and the insulation between them ... and the punch it into some formula that i don't remember off-hand.

Dan Driscoll · « **Reply #8 on:** 28 Jan 2005, 03:33 pm »

Quote from: dayneger

Thanks for the feedbacks!

So does a digital/video cable actually act like a 75 ohm resistor instead of like a wire with a fraction of an ohm resistance, which I'm assuming is how normal interconnects measure?

"75 ohms" refers to a cable's impedance, not resistance. Impedance is a measurement of the cable's capacitive reactance, inductive reactance and resistance, combined. Impedance will also vary with the frequency of the signal being transmitted through the cable, while resistance is fixed, regardless of frequency.

ctviggen · « **Reply #9 on:** 28 Jan 2005, 04:15 pm »

Here's a site that shows this visibly:

http://www.zzmatch.com/txn.html

This discusses impedance:

http://en.wikipedia.org/wiki/Impedance

Ulas · « **Reply #10 on:** 28 Jan 2005, 07:03 pm »

I wouldn’t lose sleep worrying about impedance matching for digital audio. First, any impedance mismatch is inconsequential at digital audio frequencies, <3 MHz. Impedance matching on long transmission lines becomes an issue only above 1 GHz. Second, RCA plugs and jacks are not 75 ohms no matter what anybody claims. Third, most high-end digital cables and DACs with BNC connectors mistakenly use 50 ohm BNCs, instead 75 ohms. So, whether you use RCAs or BNCs, there is already an impedance mismatch at the connector regardless of the cable used. For the short distances and low bit rates involved in digital audio, the impedance of the cables and connectors doesn’t really matter.

This is what I use: a single Cat5 twisted pair with any available RCA plug. (I happened to have an unmatched pair of Eichmann plugs so that’s what I used.) In direct comparisons, the cable pictured was indistinguishable from $100 and $3,000 “audiophile quality” digital cables.

viggen · « **Reply #11 on:** 28 Jan 2005, 08:47 pm »

Wow, that cable looks almost exactly like the one in my moniker. I used magnet wire in that one instead of CAT5 though. I did make a few digital cables using USB, CAT5 and OTA wires. The OTA is the best out of these. But, the other ones are no slouches either.

RichardS · « **Reply #12 on:** 29 Jan 2005, 05:18 am »

I hear what I consider to be meaningful differences between different digital cables. I notice more differences beween type of cable (AES/EBU vs. coax) than with lengths, sometimes even more noticeable than between different brands, though I'm not discounting that jitter/reflections may be induced in a shorter cable.

Surprisingly, some non-75-ohm analog RCA interconnects have sounded quite good in my system (notably a Von Gaylord Chinchilla) but most don't (they tend to sound 'muddy' and opaque). After a recent shoot-out of approx 12 digital cables, I've gone back to 110-ohm AES/EBU as my general preference (aided by my discovery of an Audioquest Hawk and a CRL/FIM Gold (stiff but incredibly musical). IMS, they make as much difference/improvement as my Camelot Dragon jitter-box or changing/modifying transports.

The theorists will forever argue about whether adequately-constructed digital cables matter or differ in sound. If you can't hear a difference, you've saved yourself some money. If you do, and you're an audiophile, sometimes you can't help experimenting till you find one that floats your boat. This is my third round of dig. cable experimentation over the last 6-7 years, each time with more expensive cables, and I've mostly (but not always) found the pricey ones to be better sounding. Whether it's worth it to you is a personal decision.

Tonto Yoder · « **Reply #13 on:** 29 Jan 2005, 01:33 pm »

Quote from: RichardS

.... (notably a Von Gaylord Chinchilla) .....

Sounds like a pedigreed pet more than an interconnect!

But I bet it really excites those woofers.

Ulas · « **Reply #14 on:** 30 Jan 2005, 02:03 am »

Quote from: RichardS

I hear what I consider to be meaningful differences between different digital cables. I notice more differences beween type of cable (AES/EBU vs. coax) than with lengths, sometimes even more noticeable than between different brands, though I'm not discounting that jitter/reflections may be induced in a shorter cable.

I know many audiophiles claim to hear a significant difference changing digital cables, enough for some of them to happily pay $3K for an Audio Note Sogon. I have never heard a difference nor have I heard a convincing argument telling me why digital cables should make a difference in a properly designed and implemented digital audio system. I contend that if you hear a difference changing digital cables, either your system is broken or, as a properly conditioned audiophile, you are hearing what you think you should hear.