RCA cable as Digital Coax?

[Torquelover 0]

Hi,

 

Yet another stupid question from me Can I use a normal RCA cable as a digital coax? Seems like the digital coax connectors are similar to the RCA connectors. Any impedence difference concerns? I have a few VDH RCA sitting around after my wife decommissioned my full setup a few years back.

 

BTW, thanks to all for your recommendations previously, I am now happily listening to my rig

 

Stello CDT100 - Stello DA100S - MF XCAN v8P - DT990 I can really hear detail that was not present previously in iPod - iQube - ATHESW10. The sound stage is so.... Ops, my wife is trying hard not to notice the slow increase in "headphone equipment" in the reading room. I promise her no more full floor standing speakers.

 

Cheers

Edited January 29, 2010 by Torquelover

[kchew 0]

Digital coaxial cables should be 75 ohms for best results. I think some VDH analogue interconnects are 75ohms as well, so perhaps you're lucky.

Edited January 30, 2010 by kchew

[Stereo_Electronics 0]

Hi,

 

Yet another stupid question from me Can I use a normal RCA cable as a digital coax? Seems like the digital coax connectors are similar to the RCA connectors. Any impedence difference concerns? I have a few VDH RCA sitting around after my wife decommissioned my full setup a few years back.

 

BTW, thanks to all for your recommendations previously, I am now happily listening to my rig

 

Stello CDT100 - Stello DA100S - MF XCAN v8P - DT990 I can really hear detail that was not present previously in iPod - iQube - ATHESW10. The sound stage is so.... Ops, my wife is trying hard not to notice the slow increase in "headphone equipment" in the reading room. I promise her no more full floor standing speakers.

 

Cheers

 

Digital coaxial cables should ONLY be 75 ohms, if you need a cheaper alternative, a regular video (yellow RCA cable) interconnect or antenna cable (terminate the plug to RCA) works fine too.

 

 

 

[wwenze 0]

Most if not all RCA should be 75 ohms, analogue or digital, video or audio.

[Stereo_Electronics 0]

Most if not all RCA should be 75 ohms, analogue or digital, video or audio.

 

How did you come out with that conclusion?

[:: Chicky :: 0]

Digital coaxial cables should ONLY be 75 ohms, if you need a cheaper alternative, a regular video (yellow RCA cable) interconnect or antenna cable (terminate the plug to RCA) works fine too.

Just asking, does those higher quality one provide audible difference ?

Is it significantly better... ?

 

Thanks

Edited January 30, 2010 by :: Chicky ::

[Stereo_Electronics 0]

Just asking, does those higher quality one provide audible difference ?

Is it significantly better... ?

 

Thanks

 

If you are interested, I can loan you a set of the Mapleshade's entry level digital interconnect for you to audition at home.

 

[:: Chicky :: 0]

If you are interested, I can loan you a set of the Mapleshade's entry level digital interconnect for you to audition at home.

Thank you for the offer

 

It seems that the Cambridge Audio DacMagic that I am going to purchase next week end does not come with any cables =(

So I've got nothing to compare the Mapleshade's entry level digital IC with..

 

By the way, just asking.

Optical and Coax, if both are available, which one should theoritically sound better ?

I asked as I didn't want to go through the trouble to test out which input is better, as according to the posts here, it seems that the wire materials also affect digital signal's transfer speed. Unless the 2 cables are made by the same manufacturer with the same material..

 

So yeah, optical and coax, which one ?

[wwenze 0]

How did you come out with that conclusion?

 

1) Google

 

2) The 75-ohm coaxial cable "standard" (IIRC it was never really defined but just followed for convenience) is used in phono, composite, component, and SPDIF with RCA connector, and used with many others with other connectors including TV, AES/EBU, and ethernet.

[Stereo_Electronics 0]

1) Google

 

2) The 75-ohm coaxial cable "standard" (IIRC it was never really defined but just followed for convenience) is used in phono, composite, component, and SPDIF with RCA connector, and used with many others with other connectors including TV, AES/EBU, and ethernet.

 

That would only be correct if you are referring to digital connections like (2), even so, AES/EBU digital is 110ohms.

 

Since you have googled on 75ohms, then you should also know how important it is that the cable has to be 75ohms +/- 0.5ohms to maintain digital signal's integrity.

 

Because the effects of impedance mismatch are dependent upon frequency, the issue has particular relevance for digital signals. Where analog audio or video signals consist of electrical waves which rise or fall continuously through a range, digital signals are very different--they switch rapidly between two states representing bits, 1 and 0. This switching creates something close to what we call a "square wave," a waveform which, instead of being sloped like a sine wave, has sharp, sudden transitions (in practice, the "square waves" in digital signals aren't really quite square). Although a digital signal can be said to have a "frequency" at the rate at which it switches, electrically, a square wave of a given frequency is equivalent to a sine wave at that frequency accompanied by an infinite series of harmonics--that is, multiples of the frequency. If all of these harmonics aren't faithfully carried through the cable--and, in fact, it's physically impossible to carry all of them faithfully--then the "shoulders" of the digital square wave begin to round off. The more the wave becomes rounded, the higher the possibility of bit errors becomes. The device at the load end will, of course, reconstitute the digital information from this somewhat rounded wave, but as the rounding becomes worse and worse, eventually there comes a point where the errors are too severe to be corrected, and the signal can no longer be reconstituted. The best defense against the problem is, of course, a cable of the right impedance: for digital video or SPDIF digital audio, this means a 75 ohm cable like Belden 1694A; for AES/EBU balanced digital audio, this means a 110 ohm cable like Belden 1800F.

The above paragraph taken from blue jeans cables

 

Therefore, connecting a digital jack with any cable found in your drawer thinking it's 75ohms when it's not can be quite a big mistake.

 

Thank you for the offer

 

It seems that the Cambridge Audio DacMagic that I am going to purchase next week end does not come with any cables =(

So I've got nothing to compare the Mapleshade's entry level digital IC with..

 

By the way, just asking.

Optical and Coax, if both are available, which one should theoritically sound better ?

I asked as I didn't want to go through the trouble to test out which input is better, as according to the posts here, it seems that the wire materials also affect digital signal's transfer speed. Unless the 2 cables are made by the same manufacturer with the same material..

 

So yeah, optical and coax, which one ?

 

My personal preference would be coaxial but then again it is my personal preference. This question is like asking me whether thick pizzas taste better or thin pizzas... If you need I can also loan you another Audio Technica toslink optical cable and you can decide for yourself.

 

[wwenze 0]

AES/EBU is either 110-ohm shielded TP or 75-ohm coaxial. It does not use 110-ohm coaxial.

Edited January 30, 2010 by wwenze

[user 0]

Check for your cable sleeve, if it has words that is "RG-59" then it should be 75ohm.

 

By the way the impedance is 'characteristic impedance', not the impedance(resistance) that you can measure with multimeter directly, but determined by the material, diameter etc, and no matter how long it will still be 75ohm characteristic impedance. (Of course the longer the stronger the noise interference)

[Stereo_Electronics 0]

AES/EBU is either 110-ohm shielded TP or 75-ohm coaxial. It does not use 110-ohm coaxial.

 

S/PDIF usually refers to our consumer 75ohms coaxial cable and toslink optical cable.

S/PDIF

 

AES/EBU generally refers to balanced XLR which is used in professional equipments. For balanced digital, 110ohm is the standard.

 

[kchew 0]

By the way, just asking.

Optical and Coax, if both are available, which one should theoritically sound better ?

I asked as I didn't want to go through the trouble to test out which input is better, as according to the posts here, it seems that the wire materials also affect digital signal's transfer speed. Unless the 2 cables are made by the same manufacturer with the same material..

 

So yeah, optical and coax, which one ?

 

Personally, between the two I'd go for coaxial, but I've experienced a cheap PCDP with a cheap optical cable being better than a $200+ soundcard with a Van Den Hul digital coaxial cable. System-matching plays a part here too. If I could I would go for either AES/EBU or BNC.

 

If you need more than 3 meters, coaxial would be better as there is less signal attenuation compared to optical, and coaxial cables can go around tighter corners. But if you have a lot of electronic equipment around with lots of emissions, then optical is the way to go.

[Stereo_Electronics 0]

Check for your cable sleeve, if it has words that is "RG-59" then it should be 75ohm.

 

By the way the impedance is 'characteristic impedance', not the impedance(resistance) that you can measure with multimeter directly, but determined by the material, diameter etc, and no matter how long it will still be 75ohm characteristic impedance. (Of course the longer the stronger the noise interference)

 

Adding an RCA plug and solder will change the impedance even on a 1m 75ohm cable, that's why pro equipment usually uses 75ohms BNC connectors(available in 50ohms too) on coaxial cables. The BNC connector is the industry standard, being the only true 75 ohm connector. Therefore unless we can connect bare cable into the equipment, ensuring 75ohms on a RCA coaxial cable is not as easy as it looks.