Confusion over cable type: analog vs digital audio

Erik Tracy

Ok, so I'm in a phase where I'm experimenting with interconnecting cables.

One thing that was posted here was that there might be an audible difference between toslink fiber optic digital vs coax digital between my CDP and AVR.

I've already got some Blue Jeans Toslink's now, and so was considering shopping for a digital coax cable.

On Blue Jean's website there is a section on their analog audio cables:
http://www.bluejeanscable.com/store/audio/index.htm

Down the page they describe the use of Belden 1694A cable as being "excellent for analog audio".

Ok....

Then in the section for digital 'coax':
http://www.bluejeanscable.com/store/digital-audio/index.htm

Guess what.... Belden 1694A.



And I saw something similar on monoprices site about their cable types for subwoofers and digital coax.

If so, then I could 'experiment' by using a standard RCA cable laying about to compare digital coax to digital toslink/f.o.

What am I missing here? :rolleyes:

Mike21

Hi Eric.

My understanding is as follows:

I/Cs commonly called "RCAs" are cables with RCA type connectors that carry analog signal only.

I/Cs commonly called "coax" are 75 ohm cables with RCA connectors that carry digital signals in accordance with the the Sony/Phillips Digital Intreface specs ("S/PDIF"). These cables will also carry an analog signal, but are generally more expensive than analog only RCAs. When transmitting an analog signal, coax has no advantage over standard analog only RCA.

I/Cs commonly called "Toslink" are fiber optic cables w/ Toslink type connectors that carry an optical digital signal which has a wider bandwith than S/PDIF (although this wider bandwith does not result in better audio performance than S/PDIF). Optical cables come in 2 flovors: glass and plastic. There is a debate over which is better. Optical cables will not carry an analog signal.

There is also a debate over whether coax is better than optical.

I hope this helps.:)

ben62670

You can use coax for analog. Don't use analog for coax. Coax is better than toslink(optical) Optical has two more conversions to get to the same place;) However Optical can be better if there is a noise problem. This is rare.
Ben

ShinAce

Analog IS coaxial.

It comes down to impedance. For digital, you are to use a 75 ohm cable(RG59, RG6, Belden 1694A,...).

For analog, the impedance of the cable is not taken into account.

disneyjoe7

True I use some RG6 cable for interconnects which are ran in the wall which carry audio to another amp for whole house audio. But I also use RG6 cable for TV signal which is a digital signal now also.

Erik Tracy

I understand the principles behind the differences of digital vs analog, but the fact that BJ uses the same cable type for both confuses me.

disneyjoe7

RG6 cable can make fine analog cables 20hz to 20khz, in fact they can go to 0hz DC voltage as in a satellite LNB being 13vdc or 18vdc to 4+ Ghz. The impedance of RG6 cable is also 75ohm which is what a digital coax output is, so in another way of putting this. Let's say its the proper size peg for the correct size hole, so the signal can travel unattenuated from one end to the other. Making RG6 cable fine either way, but understand analog audio can sound different with any cable used. So RG6 for analog may not be your cup of tea, in the sea of audio cables.

steveinaz

ShinAce wrote: »

Analog IS coaxial.

It comes down to impedance. For digital, you are to use a 75 ohm cable(RG59, RG6, Belden 1694A,...).

For analog, the impedance of the cable is not taken into account.

Exactly. Tighter tolerances are needed for digital transmission. This probably explains why differences in analog cables are easier to detect (usually) than digital coaxials (if properly spec'd).

Mike21

Hey Eric.

Next time you post a question, ignore my reply and listen to these others dudes.

disneyjoe7

Hey Mike,

I read your post I seen nothing wrong in what you posted.

I think Eric is still confused on why so many like I tried to explain why in terms he may understand.

Steve

John K.

Erik, Blue Jeans(and others)uses the same cable for both purposes because a cable with an impedance close to 75 ohms, which is desirable for digital data(although not crucial for distances of just a few feet)of course will also work for analog data transmission, which doesn't require any specific impedance connection.

On the optical vs coaxial question, while experimentation is good, both are carrying digital data and shouldn't differ with other factors being equal. A factor which isn't necessarily always equal is that the optical and coaxial outputs/inputs may differ slightly in output level/input sensitivity, making one slightly louder than the other and sounding "better", although there's no inherent quality difference in the two(other than the immunity to electrical interference which the optical cable possesses).