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Hi;I'm going to order a few different digital rca cables to audition for a couple of weeks to see which one works best in my system, and send the others back.
Question: Does the cable length play a significant part in the sound?
I ask because I can get by with a 1/2 meter cable.
........I was a vegetarian for 15 minutes... until the main course.
Edits: 04/07/14Follow Ups:
Yes, depending on the impedance matching accuracy of your transmission system. Longer cables are fine as long as your transmitter and receiver are as close as possible to being perfectly matched with the cable over the entire bandwidth required by the signal. In the real world this rarely happens with consumer grade equipment so you want the shortest cable you can get away with without introducing sharp bends in the cable - particularly near the strain relief of the connector as this will put a torque on the connector in the socket and can cause poor connections and potentially signal distortions due to the dielectric being deformed. It also depends on the primary sample rate which defines the propagation time (and the bandwidth of the signal). Basically you don't want standing waves messing with the transmitted pulses. If the reflected pulses are of a sufficiently low amplitude and/or out of phase with the transmitted pulse, you should have no problem. The receiver PLL should be able to lock on to the primary signal without problem and be largely unaffected by low amplitude reflections - the jitter tolerance of the SPDIF spec is of the order of nano-seconds. To put this in perspective jitter levels within the DAC at the reconstruction stage need to be of the order of pico-seconds. Good receivers are designed to handle such signals and recover the clock and data correctly with minimum output jitter. From memory the standard (IEC60958-3) defines something like 50ps for receivers. Old devices prior to this standard such as the CS8414 have an intrinsic jitter of 200ps which is still an order of magnitude less than the transmission jitter. The problem comes when the transmitted pulses become distorted by the reflections when the geometric length of the cable is related to the transmission frequency. The receiver then has difficulty establishing the transitions from the bi-phase coding.
It's not just the cable, the connector needs to be 75 ohm matched as well as the source and receiver - the best cable in the world won't fix that problem! Any problems in impedance matching will cause reflections to be set up. RCA connectors are notoriously poor for RF terminations as they are not generally impedance matched for 75 ohms, so make sure the connectors are cleaned first and try and minimise the number of times you insert and remove. If you can, I recommend switching to BNC connectors on your transport and DAC.
"Beauty is Truth, Truth Beauty.." Keats
Chris Sommovigo, who knows digital cables pretty well, makes his Black Cat Silverstar! 75 in 1.23m only. I can quickly switch back and forth between his cable on S/PDIF and the AES/EBU cables I have also hooked up and I always prefer Chris's S/PDIF cable over the balanced cables.
Not true...he offers .75 meters too.
Cabledyne also offers .7 meters with a variety of connectors.
I found the site and ordered the Silverstar 75.
I'm sure it will be perfect.
Thanks again.
........I was a vegetarian for 15 minutes... until the main course.
Thanks;
Do you happen to have a link?
........I was a vegetarian for 15 minutes... until the main course.
I think that I compared fibers in 3 foot vs 25 feet a while ago and the longer was much better. I'm using 1 m for my coax, since a long one with quality would be very expensive, although, depending on the DAC a long cheap RCA may be better than a short good cable.
sbrians wrote:
"I think that I compared fibers in 3 foot vs 25 feet a while ago and the longer was much better."
If by fiber, you mean fiber optic, digital optical cables (Toslink) can be substantially different in how they behave regardless of length. Just because a specific long Toslink cable sounds better than a particular short length Toslink cable does not mean functional length makes a vital difference in terms of essential SQ.
"I'm using 1 m for my coax, since a long one with quality would be very expensive, although, depending on the DAC a long cheap RCA may be better than a short good cable."
That depends of what you mean by "cheap" and "good". Inexpensive cables with mediocre designs won't tend to sound better than more expensive cables with superior designs, regardless of length.
.
Great, thanks you for the advice.....
........I was a vegetarian for 15 minutes... until the main course.
It is not just a matter of, a minimum of 1.5 meters.
Rather, 3 feet/1m and their multiples and fractions are to be avoided.
So, 1.5 meters or 3 meters, but NOT 2 meters.
What is important is not the length, but the time of the arrival of reflections from the far end.
If components are close, there is no reason I can see that .75m should not work, but nobody makes those as a stock item. Cardas will chop and re-terminate a 1m digital cable for a surcharge over the 1m cable.
Hope that helps.
JM
When this topic came about a few years ago I asked some of the heavy hitters in cable design, serious players, as well as pro mastering and recording engineers and overwhelming consensus was this theory about cable length is total and utter BS. I concur.With a gun to your head you could not pick out a .5m, 1m, or 1.5 cable in use.
FYI, Audioquest sells .75M stock digital cables
Edits: 04/09/14
concept came from Bob Fulton. He claimed that one meter was the length of your car antenna so 1 meter cables made perfect antennas for a lot of RF. Of course he built analog cables, so I am not sure of the applicability of his ideas for digital.
Borrowing his idea though, remember those stubby antennas for early cell phones? Pretty short: I seem to remember just three or four inches.
FWIW
That's an interesting notion, unclestu. But cable reflections are a result of improper impedance of cable terminations (and/or the cable itself) that actually cause the reflections in the first place, while the ideal cable length manipulates the timing of the reflections, which mitigates the aspect of reflections that actually affect the digital I/Os.
That said, the RF observation is an still interesting idea about the topic ;-)
is a tool, a reflectometer or perhaps it has some other name which shoots an impulse signal down the cable and then measures the reflections. I've seen it in use ( military test lab) and its pretty cool. It will tell how far down the cable length where the reflections are being propagated.
It will do it for coax as well as CAT 5/6 cables, where often times a mere pinching of the cable bundle can cause issues. I see them every so often in Military surplus auctions but never won one yet.
The machine was being used on board a Sub to check out the recently installed wiring harnesses.
The tool was interesting because it points out other possible issues which may cause unwanted reflections
In my scenarios using a digital cable I had a 1/2 meter Vampire that I first used with a transport. Switching to the Silflex per your rec was a huge improvement. When I then switched the source to a SB III with the same DAC (Trivista SACD w/dead transport) I felt the Silflex too bright and tried the Vampire again and it was great no longer suffering from the grungy-ness present when using it with the transport.
Out of curiosity I'd like to try a different digital cable at some point but don't have any disposable income right now.
ET
What model is your particular 0.5m Vampire digital coaxial cable?
Its a modified RG 226.
Got it from a surplus satellite uplink for our local phone company. Heavily silver plated, and with silver plated shielding braid.
What is unusual is that the center conductor is in a plastic tube (not teflon) and there is a strand of polyethlene or something similar wound around the center conductor to center it in the tube.
Sounds very good: Similar to the Illuminati D-60. With 75 ohm ends sounds the equivalent if not better (IMHO).
Had it tested once and it was flat out to 2 Ghz. Never seen it listed in any catalog, but the original had mini BNC's stamped with a KS part umber which I assume was WE.
I'd try it out if you'll set me a foot and a half.
ET
I can't remember, it's from the early 2000's has a thick blue cable and RCA's that unscrew somehow. By tomorrow I will take a pic of it and post. Thanks.
ET
Excellent, Awe-d-o-file. I might be able to steer you towards a fine sounding DIY build that's likely affordable.
Cheers, Duster
Here is the old Vampire-ET
That's actually a classic UP-OCC digital coaxial cable made by Neotech. Vampire terminated the cable with entry level brass Vampire Tiffany style rca connectors and marketed it as the Vampire DI-1 digital cable.
A version was previously available (now discontinued) as a Neotech ND021090 cable from Take Five Audio with upgraded copper Vampire Tiffany style rca connectors:
http://www.takefiveaudio.com/mall/shopexd.asp?id=1058
The same version is still available from another seller, but priced substantially higher than Take Five Audio:
http://www.douglasconnection.com/Neotech-Digital-Interconnect-and-Vampire-Wire-9X-CB-NVDIC.htm
You had mentioned you might have a DIY I may want to try. Now that you know what I have do you still think I should try it? Thanks in advance.
ET
Great,I'd like to try that. I'll get the pic up later today.
ET
I kindly thank you and the others for your response and knowledge of the subject matter.I don't mind spending money, but I hate to spend it foolishly.
After reading your response I was brought back several decades (the 70's) to when I was a young kid. I can remember my uncles fooling around with cb radios and how they were always concerned with keeping the antenna cable to multiples of 3 feet (3,6,9,12 etc....). I do not know or not if it's similar here or not.I was perusing the Dh Labs site and came across their D-750 cable with diy instructions for termination; So I think I will give it a go.
Thanks again.
........I was a vegetarian for 15 minutes... until the main course.
Edits: 04/10/14
It tends to depend on what make/model cable/connector, and/or what make/model components (both transport and DAC) the digital coaxial cable is placed between (synergy tends to be the key).
The prevailing wisdom as being a safe bet is 1.5m, while a 0.5m length tends to be less of an issue than a 1m length.
Equally important is the type of connector and termination method involved in a digital coaxial cable build in order to mitigate cable reflections rather than just rely on an ideal length to address the matter.
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