What 's so special about a digital interconnect?

albee · « **on:** 25 Aug 2005, 08:17 pm »

Is it a simple regular i/c or is it made from something special. I can understand an optical i/c but the digital thing has me puzzled.

PhilNYC · « **Reply #1 on:** 25 Aug 2005, 09:13 pm »

The main characteristic of a digital cable (SPDIF/coax) is that it has an impedence of 75ohm (same as component video cables). This is important in order to make sure there is no signal reflection that occurs within the cable that might cause problems in the receiving component (assumes that the digital out and digital in are also true 75ohm, which is how SPDIF is specified, but often not implemented quite accurately)...

Carlman · « **Reply #2 on:** 25 Aug 2005, 09:28 pm »

I do not think RCA connectors are 75 ohm... but for some reason they're the standard output and are called 'coax'... but a BNC connector is all I know that is truly 75ohm. I have a 'digital cable' from Audience which is a single run of interconnect cable.

Any regular interconnect cable will work. I think some manufacturers may be able to get there cables to show a 75ohm resistance with the way the cables are built... so, cable plus connectors = 75ohm. I don't know if this is true. However, I'd bet sound quality changes with digital IC's are impossible to predict because of the resistance issue and various lengths...

It's somewhat of a potshot as to what digital IC works well for me. I've heard some minor differences from one cable to the next but what I really don't understand is why optical isn't the standard. NO EFI, RMI, and 'should' be bit perfect. In my experience with cheap optical is that it has more of a digital haze to the music over a good digital IC using RCA connectors.... on a cheap DAC... However, on better DAC's like a Museatex I had, cables made little or no difference.

Have fun!

PhilNYC · « **Reply #3 on:** 25 Aug 2005, 09:45 pm »

Carl,

I had an interesting conversation with a DAC manufacturer recently, talking specifically about the difference in performance between a BNC and RCA connector on a SPDIF coax cable. He said that he was firmly in the BNC-is-better camp until a new RCA from Eichmann was recently released...to which he said "I haven't measured it, but it sounds better to me".

Per Steve Nugent's article on Positive Feedback last year, I've found that digital cable length made more difference than anything else (and something between 1.5m-2m was idea for an unmodded transport). That said, as much as I hate to write this about one of my manufacturers, I've found that cables claiming to be "true 75ohms" have generally (to my ears) outperformed the Audience au24 digital cable (which does not make the 75ohm claim).

I will soon have the opportunity to try out 3 of the same cable (Acoustic Zen Silver Byte - "true 75ohms"), one with RCAs on both ends, one with BNCs on both ends, and one with RCA on the transport and BNC on the DAC...all 1.5m in length. The 3rd cable is one that should tell a lot, because according to Steve's theory, if the DAC-side cable is true 75ohms, you won't get that reflection back up to the transport, so it should be a good representation. The issue with the RCA-RCA comparison against the BNC-BNC is that I'll have to use different digital outs on the transport....

tianguis · « **Reply #4 on:** 26 Aug 2005, 01:31 am »

Phil:
I've experimented with many "digital" cables and terminations, including RCA and BNC, also including various lengths of 50 ohm. Very short works, as does over 5 ft. However, true 75 ohm cable sounds better to me. I've spent mucho bucks on "digital" cables from respected cable folks, copper and silver, and they all suck compared to what I make. Mine is not "user friendly" but it does kick butt. Ya gotta wrassle with it. Wanta listen?

Larry

PhilNYC · « **Reply #5 on:** 26 Aug 2005, 03:38 am »

Larry,

I would guess that "true 75ohms" would eliminate the need for a 1.5m cable length...

And yes, bring it on! Would love to try out your cable against my AZ stuff!

Bemopti123 · « **Reply #6 on:** 26 Aug 2005, 03:49 am »

Shit. Larry, sign me up for a listening and I just purchased an Illuminati D-60 1 meter. Dang.

Paul

mcrespo71 · « **Reply #7 on:** 26 Aug 2005, 05:30 am »

Quote from: Bemopti123

Shit. Larry, sign me up for a listening and I just purchased an Illuminati D-60 1 meter. Dang.

Paul

I owned that cable for quite some time (it was a great design), but it later got spanked by a much cheaper stereovox HDVX cable, so I sold it.

Michael

albee · « **Reply #8 on:** 26 Aug 2005, 03:03 pm »

Thanks for the education. I have a pair of Mapleshade IC's and noticed they sell just one as a digital cable. I was wondering if I could use one of mine, then again, the actual connector could be the difference, right?