Are 75 ohm digital video and audio cables the same?

[diamdiam]

I was wondering if there's any difference between 75 ohm digital audio and video cables. I've noticed that a lot of people use belden video cables in audio applications. Thanks

[jewilson]

Yes there are differences in 75 ohm cables. All the 75 ohm stuff is not designed for TV signals either. Also, all the 75 ohm cables don't sound the same.

[diyman]

I have used RG58 and RG59 cables for audio. Generally, I find the sound very clean but a bit clinical. It does not have the so called "air" or "bloom" the better regular audio cables have. I have very good results using ultrafine magnet wires as interconnects but care must be taken on the screening of the wires to get optimum results.

diyman

[Aud_Mot]

Belden 1694A is the most popular 75 ohm coax cable for broadcast video. The most demanding broadcast signal is baseband high definition digital video. (SMPTE standard 292M) It has a data rate of 1.45 gigahertz.

In fact SMPTE 292M has 8 AES/EBU (almost identical to S/PDIF) digital audio streams (equvilent to 16 mono signals) embedded in the video signal. It is a very hearty cable. It is good with HD digital to 100 meters.

Belden also makes a physically smaller (about the size of a pencil) that is a more flexible cable (I forget the number) that is good to about 30 meters, on HD digital video.

Belden also makes 1800A a true 110 ohm balanced twisted pair cable for AES/EBU digital audio applications. Easier to terminate becuase it uses XLR connectors.

As to which 75 ohm cables sounds better, I won't get into that. I do know that the Belden cables are well engineered with very tight quality control. To use them on S/PDIF or other digital audio signal would probably be over kill, but that is the fun of this forum, exploring overkill.

If you can get your hands on either the 1694A or 1800A, I would recomend you make up some cables and listen.

Aud_Mot

jewilson,

"All the 75 ohm stuff is not designed for TV signals either"

I do not understand what you mean by this, can you eloborate?

[diyman]

I have used Belden RG59(75 ohms) as SPDIF cables with very good results. Particularly when I changed all the connectors to 75 ohms BNC (plugs and source sockets). No boutique parts needed just good industrial grade ones will do eg. Amphenol etc.

Just my 2 cts

diyman

[diamdiam]

Thanks for the responses. I picked up some cheap bnc cables using belden 1505a that were originally designed for video production. I am going to change the rcas in my dac and transport to bncs. I just wanted to make sure it'll work.

After doing some surfing, the digital cables I've seen work for both audio and digital e.g. kimber cables, blue jean cables.

[jewilson]

You should also look at Beldon RG187 silver plated Teflon.

[Pitch254]

For SPDIF transport over a transmission line, a couple of things are important:

Cable impedance
Shielding
Termination and connectors
Damping per 100 (or xx) meter in dB´s

It´s just some sort of AC (topped of blockwaves) running over it. Use of exotic materials are not "audible"

So use off the shelf RG 59 cable (75 Ohm). If you have to cross long distances, use the thick version of this cable. (Forgot the type) and use 75 Ohm BNC or better, F-connectors.
BNC, from the "somwhere in a drawer found type "are often 50 Ohm and it´s often impossible to check.

THat´s all there is.

[jewilson]

Pitch254

RG187 is 75ohm impedance cable, the teflon help lower the capacitance of the the cable and silver plating is a bonus. The RG59 is great for TV's but and it's not easy to terminate unless you use F connectors and it a ***** to bend.

The standed stuff is much better for this application. If you going to the trouble to get BNC connector get 75ohm versions.