Digital Coaxial cable? Can I just use a standard phono?

rossyl

Standard Member
As above.

Digital Coaxial Audio cables seem to cost £20+.

Will a standard phono cable work and provide comparable sound quality?

thanks
 

pjclark1

Novice Member
You can use anything you can find.
1/2 of a stereo cable works fine.
 

PH001

Active Member
Are you sure about that 'cause I tried it once and got no signal through at all. Are standard phono leads 75ohm impedance? I think they need to be for digital coax?
 

spl23

Well-known Member
Are you sure about that 'cause I tried it once and got no signal through at all. Are standard phono leads 75ohm impedance? I think they need to be for digital coax?
Technically, yes, you should use a 75ohm cable - unfortunately, it is extremely difficult to make a phono plug that has a 75ohm impedance, and most companies don't even bother. (I'm only aware of one manufacturer who claims to make a 75ohm phono plug - can't remember who they are at the moment...)

So even if the cable is 75ohm, the plugs generally aren't, and you'll find the signal still gets through. Pretty much any phono cable will work, and it really isn't worth spending huge sums of money, as it will make no difference to the sound.

If you really want to be sure, get a phono to phono cable designed for composite video (such as used for hooking a camcorder up to your TV) - that will be designed for higher frequencies than a bog-standard audio cable. But even that really isn't that important.

Anyone claiming that a particular digital cable will give better sound, clearer highs, more pronounced bass etc is talking nonsense!
 

pjclark1

Novice Member
If something is designed to be used at a certain specification why would you want to not do this rather than just save a few quid?
That's because no cable using phono is designed for digital signals. Phono connectors are 50 ohm, if you wanted 75 ohm you would need a BNC connector.

Digital cable manufacturers and retailers lie .... all the time.
Their are 10 types of digital cable buyers, those who understand the lie, and those that don't.


"A delicate digital AC-3 signal originating from my $4500.00 Theta DaViD transport THROUGH A WIRE HANGER?!?" ***

Calm down Mrs. Crawford, yes, through a wire hanger... It'll work just fine...

Ok,

So if any of you followed the digital wire wars a while back you may recall that some people maintained that you absolutely, positively, NEEDED a 75 ohm digital cable to connect your DVD player to your pre/pro... Nothing else will do... Anything else, and you risk errors in the bitstream so bad, that they are not only uncorrectable but you will also lose that "smooth airiness on the highs; open and more believeable soundstage; (insert your favorite audiophile tripe here)" and that basically the more money you spend on a digital cable, the more likely you are to achieve a sonic nirvana.

And you may or may not remember that after some rumblings and an e-mail from Jon Wenger, I built "The Finest Digital Transfer Wire In-the-WORLD!"® by taking two blue painted wire hangers and cutting an old, cheap, ugly green rca patch cord in two, soldering the ends onto the wire hangers.

You may remember my initial listening tests between that, a cheap, ugly yellow patch cord, a proper RG-6, 75 ohm cable with gold rca's, and the optical tos-link for comparison, yielded no discernable results, BUT there were too many other factors, like my ears may not be as golden or magical as someone else's, or that the toslink was shoddy anyway, etc.

Well, with Jon's help, I have now finished lab testing the cable.

For the dvd player, we used a professional version of the Sony 7000 reference player. It's actually model number DVP-S7000TP, serial # 2023. This is a pretty cool player... it has a nice gray matte, professional looking face, with a really cool rotary region selection switch near the headphone jack! For the processor we used a Dolby Labs model number DP562 multichannel ac-3 decoder, serial # 500280. The very cool feature, which is very necessary for our scientific experiment (since my pedestrian ears can't be trusted to be refined enough for the audiophiles whose heads travel in extra rarified air,) of this Dolby produced decoder is that it will do a bit error rate count... Yup, it will count each and every error it sees... Which is crc (cyclic redundancy check) protected which means the odds of having multiple errors such that the crc check passes an error in the data stream, is almost impossible. The output of the dvd player is an rca coax connector, and the input to the decoder is an XLR balanced connector. Jon normally has a Canare XLR to rca wire connecting the two.

I brought all my wires in case the number of errors that the wire hanger wire rolled was so great, that we would want to try the others and tabulate results... If you would like to see a picture of the wires (including the Sky-Blue/Lime-Green model of "The Finest Digital Transfer Wire In-the-WORLD!"®) go to: See a photo of the wire on my main Home Theater page.


Now we initially had a little problem with the hookup because we planned on using an rca female to female adapter and putting the test wire right between the Sony 7000 and the Canare cable, BUT we could not find the female to female... Not wanting to give up without giving it the old college try, Jon found two wires with alligator clips on them, so we used those.

So just to recap this thing to death, we had: The professional Sony S7000TP reference dvd player, going to a 20 year old, ugly green, rca patch cord which was cut in two. On one side of the green rca I soldered a blue painted wire hanger to the shield and another to the center conductor. I soldered the other ends of the wire hangers to the other half of the ugly green rca patch cord. We then clipped the alligator clips with thin wire to the centers and shields of the rca connectors of my cable and of the Canare cable, and then plugged the other XLR-balanced side of the Canare into the Dolby Labs decoder. I honestly did not know how badly we would be rolling errors on this one... and with open, scientific minds, we played a dvd...

Are you all sitting down? Good. We played the King Crimson Deja VROOM dvd for over fifteen minutes with this configuration and not only did it sound good, but the Dolby Decoder reported ZERO errors... Did you all get that ok? ZERO, nadda, nihil, zippo, nothing, none... error-free. Given that, there was not much point in trying the higher quality cables I had brought with me.

Conclusion: IT DOES NOT MATTER WHAT YOU USE FOR YOUR DIGITAL CABLE CONNECTION BETWEEN YOUR DVD PLAYER AND YOUR PROCESSOR... YOU CAN BASICALLY USE ANYTHING THAT LOOKS ELECTRICALLY LIKE METAL. IT WILL WORK JUST FINE. (Between the coax connectors that is... I have not successfully used the wire hangers on the tos-link optical connectors... yet...) If you like you can hook the shield on one side to one of your Rodan bronze statues, and the other shield to somewhere else on the statue, and then hook the center conductors to another Rodan bronze, and it will work JUST FINE. The sonic clarity will be stunning, as well as visually pleasing.

So you can use the rca cables they throw in for free into your component boxes that you've been meaning to throw away for months because they offend your sensibilities, or you can spend hundreds of thousands of dollars on Rodan Bronzes and use those, or anything in between... but please do not tell me that it sounds "warmer, cleaner, more open" or anything like that BECAUSE of the WIRE... It may sound different to you or to others... There are lots of reasons why it MAY sound different, not ALL of which are in your head... If it in fact IS different, then this difference is NOT due to the $800 wire you just swapped in. It may be that your player or decoder are somehow defective, or not designed very robustly (i.e. - if there is a difference that is NOT your imagination, then something is broken and you should not be wondering about the wire... you need to look elsewhere for the answer...)

Lastly, if you remember, my original preliminary offer was to sell this cable - "The Finest Digital Transfer Wire In-the-WORLD!"® to whomever wanted one, for a check or money order for $750.00 and two soiled shirts and I would send you the cable, in your choice of designer sky blue with lime green ends, or designer bone shell white with banana yellow ends, and your shirts laundered... However, in light of the new lab-tested/hand-made nature of the cable, I am going to have to bump up the price. Yes, you guys had your chance, I am going to have to raise the price to $1249.00 and two soiled shirts. Keep in mind that this is for an error-free, lab-tested on official Dolby lab's equipment, cable. (Don't worry Jon, I'll split the profits with you for an occasional, over the weekend testing session!)

I've pretty much completed this experiment to my satisfaction, and believe I have beaten the proverbial dead horse to a bloody pulp... If someone thinks I may have overlooked something however, my mind is not closed on this topic, and I would be happy to address any serious scientific hypothesis regarding this or other results... Thanks for paying attention... It's been real... Remember, do have fun with your hobby... you are doing this for fun aren't you?"


http://2eyespy.tripod.com/id3.html
PS Some people think that ALL cable hype is lies, I tend to agree.
http://www.roger-russell.com/wire/wire.htm
 

spl23

Well-known Member
If something is designed to be used at a certain specification why would you want to not do this rather than just save a few quid?
Because for a short run carrying SPDIF, it really doesn't actually matter! As long as the cable works well enough for the receiver to detect a 1 as a 1 and a 0 as a 0, you can use whatever you like, and a bog-standard giveaway analogue audio cable will do this perfectly well in most cases.

SPDIF is digital - all you need to do is make sure you aren't getting bit errors at the other end, and if you are, they will be very noticeable as audio glitches. And before anyone mentions jitter - that is a timing issue, and unless someone can produce a cable through which electrons flow at different speeds from time to time, a cable can't introduce any jitter.
 

spl23

Well-known Member
Will a standard phono cable work and provide comparable sound quality?
Oh, and just to clarify one point in the original question - a standard phono cable will not just provide "comparable" sound quality. It will provide *identical* sound quality to an expensive digital interconnect...
 

KingKrell

Novice Member
Are you all sitting down? Good. We played the King Crimson Deja VROOM dvd for over fifteen minutes with this configuration and not only did it sound good, but the Dolby Decoder reported ZERO errors... Did you all get that ok? ZERO, nadda, nihil, zippo, nothing, none... error-free.
I agree with this remark; anything can transmit the data that conducts.

But just to upset the apple cart, in my experience digital cables sound different over SPDIF. I cannot say about bitstream etc. I use one for CD transport to DAC, and even on a Benchmark DAC 1 I here differences in presentation.

I found the Stereovox XV2 is much better than a Van Hen Hul First Ultimate, being smooth and open. A Belden Canare is different again, more grainy, with a cheaper RCA copper along cable being the worst (very grainy/shrill). I tried a Chord Signature, which was very forward and tight, but too forward in my system.

Despite other tests, these are my own personal findings. It's also odd, but I find digital cables of similar constructions to analog equivalents have a similar effect on the sound. Also, the more sensative the equipment, the more you notice it. So similar sounding cables on some systems may sound pretty much the same. That's just in my experience..!

As for blind tests, I feel the ears can get tired over just a few hours and it makes such a test fatiguing. The key is to know the music and realise changes over a longer time frame. Cables offer subtle difference in the grand scheme of things, but this subtle difference can affect the presentation of the music significantly enough to warrant the cost IMO.

The key is to try yourself (I'm not after a cable argument!)... Plus it's not all about money. I now use an Ebay silver interconnect that I feel beats a Kimber AGDL on smoothness, so I'm all about design and quality, not the money. The XV2 is less than half the cost of a Chord Signature too.
 

spl23

Well-known Member
It's also odd, but I find digital cables of similar constructions to analog equivalents have a similar effect on the sound.
This remark shows what the issue is - it's classic expectation bias. Digital data transmission is *completely* different from analogue transmission - there is no way that the two are even comparable. Cable construction doesn't enter into it - while a particular construction of cable can conceivably affect the frequency response in the analogue world, the same construction will have no such effect in the digital domain. What is happening is that your brain is subconsciously using the knowledge of the sort of cable you have used to shape your perception of what you are hearing. This is precisely why double-blind tests are so important - they are the only way to eliminate the effect of expectation.

Or to put it another way - you haven't actually *heard* any differences between digital cables. You have expected a cable to have a particular effect on the sound - or even wondered whether it might do - and that information is enough for your brain to deceive you about what you are hearing. You have then probably reinforced this by listening with active expectations - you've wondered whether a cable might do something, you've "heard" it doing so, and now you will expect it to have that effect in the future - so that's what you will hear.

There is no known mechanism whereby two digital interconnects could possibly sound different. The situation is exactly analogous to HDMI cables - it is now slowly being accepted that all HDMI cables (within reason) produce exactly the same picture. In the same way, all digital audio cables will produce exactly the same sound.
 

spl23

Well-known Member
I knew I shouldn't have posted anything after I saw spl23 had.
Why? The article you posted was fair enough - I don't think Blue Jeans were claiming anything that was untrue. However, the simple fact is that matching impedance really isn't critical on SPDIF connections - if it was, then the original specification for SPDIF would have stipulated the use of proper 75ohm BNC connectors rather than phonos, which (as the article quite correctly observed) are very difficult to make with 75ohm impedance due to the geometry of the plugs. An SPDIF connection isn't 75ohm at either the source or the sink, as it goes through a phono socket at both ends. Given that, the impedance of the actual wire is rather irrelevant - all you need it to do is not pick up so much noise that bit errors are introduced.

I'm sorry if you find my quoting real engineering rather than audiophile gobbledigook offensive, but I really don't understand why - I'm just trying to save people money. (If the cable companies lose money as a result, I'd regard that as a bonus... ;-) )
 

stevebez

Novice Member
The only thing to affect a cables peformance is interference... so decent shielding is usefull. The rest is pure snake oil in my opinion.

Unless you go BNC or Canare Phonos you wont get 75ohm impedence. In any case I have not noticed a difference in picture quality with component signals anyway. (75ohm vs 50ohm).

You just have to look inside a hifi component and see what terminals are used for audio, video and digital connections - they are all the same.... so I doubt 75 ohm Canares would make any difference anyway.

I would say placing your cables next to / away from your power cords are many many magnitudes more important than what the cable you are using is made up of. Clean contacts, shielded and thats all you need.

Dont get me started on speaker cables ... again look inside any top of the range speaker unit and see what they use... staggering what people put in between their speakers and amps ... at least it does look very nice.

:)
 

Alan Mac

Active Member
Just out of curiosity, I made a few rough measurements on a “standard phono cable” - in my case a “freebie” phono cable that came with (IIRC) a DVD player. It’s the typical thin twin audio cable with phono plugs at each end.

My network analyzer is 50 ohm, so two minimum loss (5.7 dB) matching pads were used to provide a 75 ohm source and “sink”.

50 ohm “N” to BNC and nominally 75 ohm BNC to phono adapters were also used.

Phono cable length: 1.2 m
Nominal impedance : unknown

Measured Results:

Amplitude versus Frequency response:

6 MHz -0.12 dB
100 MHz -2 dB
330 MHz -3 dB
800 MHz -6 dB

Frequency-domain amplitude ripple, with a periodicity of about 60 MHz, was about +/- 0.5 dB , presumably due to impedance mismatch.

Group delay versus frequency response:

500 kHz to 1.3 GHz: 8 ns average with +/- 1 ns ripple (again probably due to mismatch)

Comments:

The frequency response up to 6 MHz is near perfect.
So for standard definition video this cheap phono cable is fine.

For SPDIF it is also fine. There seems no justifiable reason to employ anything more expensive.


Alan
 

CJROSS

Well-known Member
Comments:

The frequency response up to 6 MHz is near perfect.
So for standard definition video this cheap phono cable is fine.

For SPDIF it is also fine. There seems no justifiable reason to employ anything more expensive.


Alan
Alan, other than "audiophile nervosa" that is :smashin:

Another vote for standard screened coaxial cable as cheaply s you can source it :D
 

Schwenk

Standard Member
Just received my new HT equipment, but I did not have the cables yet....I bought some cheapo rca video leads, let´s say, thickness of a shoelace and it works perfect with my HTPC connected to my Yamaha receiver. It recognizes, DTS, PCM Stereo and Dolby Surround perfectly....so why spending lot's of $$$$?:clap:
 

tommyb1

Novice Member

JohnWH

Active Member
...
The frequency response up to 6 MHz is near perfect.
So for standard definition video this cheap phono cable is fine.

For SPDIF it is also fine. There seems no justifiable reason to employ anything more expensive.


Alan
Although correct you would need to take into account return loss at longer lengths i.e. anything approaching a 1/4 wave length of the highest frequency involved. So for SD video and SPDIF impedance effects become significant at about 12.5m (C/6MHz), so 6m is probably about as long as you want to go to be safe, beyond these lengths a cable with the wrong impedance will start causing serious problems.

John.
 

spl23

Well-known Member
What's your thoughts on the use of video composite leads (yellow phono) as:

A sub lead?

Analogue audio leads?

I've got two available, but not sure how well they'll work:

see: http://www.avforums.com/forums/showthread.php?t=720542

cheers
Absolutely no problem to use for either purpose - a composite video lead should (in theory) have decent shielding, which is pretty much the only requirement for a sub cable. (Sending signals below 200Hz down a cable is trivial - the only worry is not picking up mains hum.) Any cable designed for composite video will also comfortably be able to carry full range audio.
 

JohnWH

Active Member
Because for a short run carrying SPDIF, it really doesn't actually matter! As long as the cable works well enough for the receiver to detect a 1 as a 1 and a 0 as a 0, you can use whatever you like, and a bog-standard giveaway analogue audio cable will do this perfectly well in most cases.

SPDIF is digital - all you need to do is make sure you aren't getting bit errors at the other end, and if you are, they will be very noticeable as audio glitches. And before anyone mentions jitter - that is a timing issue, and unless someone can produce a cable through which electrons flow at different speeds from time to time, a cable can't introduce any jitter.
Jitter over spdif is not a function of the speed that electrons travel down the wire it is a function of how well the recieving device is able to recover the audio clock from the serial data stream. This is entirely an analogue function, and the more a cable effects the signal the harder it is to accuratelly recover the clock, reflections casued by impedance mismatch can have particularly nasty effects on this proces.

That said, for a cable to have any measurabel impact on jitter in the recovered clock you would need a pretty appaling peice of cable, or a very badly engineered recieving device.

John.
 

Alan Mac

Active Member
Although correct you would need to take into account return loss at longer lengths i.e. anything approaching a 1/4 wave length of the highest frequency involved. So for SD video and SPDIF impedance effects become significant at about 12.5m (C/6MHz), so 6m is probably about as long as you want to go to be safe, beyond these lengths a cable with the wrong impedance will start causing serious problems.

John.



I take your point John, about long lengths, though these cheap phono cables are normally only supplied in lengths of less than 2 m or so.

The signal takes 8 ns to travel 1.2 m

so its speed in the cable is 1.2 m / 8 ns = 150 Mm/s

(which is about c/2 )

So the wavelength of a 6 MHz signal in the cable is:

(150 Mm/s) / 6 MHz = 25 m

and a quarter of this wavelength is 25 m / 4 = 6.25 m

So perhaps 3 m might be considered the safe limit.


Alan
 

KingKrell

Novice Member
Or to put it another way - you haven't actually *heard* any differences between digital cables.
I've already reached my own conclusions as many other people have, so I don't need to be told what I hear - I hear what I hear. Comparing something like a Chord Digital Signature to a Stereovx XV2 are soooo different IMO. SPDIF data is transfered by an analog method so may explain the tonal variations I hear.

I just don't understand how people can't hear those differences. I'm going to leave it at that. I don't want this same old argument again! :suicide:.
 

Oli

Active Member
I've already reached my own conclusions as many other people have, so I don't need to be told what I hear - I hear what I hear. Comparing something like a Chord Digital Signature to a Stereovx XV2 are soooo different IMO. SPDIF data is transfered by an analog method so may explain the tonal variations I hear.

I just don't understand how people can't hear those differences. I'm going to leave it at that. I don't want this same old argument again! :suicide:.
And to be honest - no offence intended - i don't think anything will persuade yourself or others that there the differences are in your head!! :)

Having said that, I'd quite like to be at an A/B/X test with you to see the results :)
 

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