[Dan Banquer]

Folks,
This is a very good thread. I think differences between exorbitantly priced digital cables comes only from the varying impedence of the cables. If it so happens that the cable's impedence matches your output/input impendences, then that is your high-end cable. I have tried various digital cables with my Philips 963sa and Panasonic XR55 digital amp receiver. Right now, the $30 glass toslink sounds the best to me.

I'll bet the opto link sounds best because there is no ground connection between the two units. Given the near total lack of any grounding standard in consumer audio your observation does not surprise me.
              d.b.

[jneutron]

Randy

For a cable, measure L and C and calculate Z.  it will be =sqr(L/C).

Measure L with the far end shorted.  Measure C with the far end open.


For an output or an input, put a 1K resistor in series with a sine gen into the output.  Push 1.075 volts in, to force 1 milliamp current. (close enough).  As far as I am aware, no equipment should be damaged by forcing one milliamp into an input or an output. (anyone out there differ on that?)

The voltage measured at the output or input will be the drop caused by 1 milliamp into the impedance.  The equip you are measuring should be live, btw.

If the output is 75 ohms, you will measure 75 millivolts.  Same with the input.

Cheers, John

[jneutron]

I'll bet the opto link sounds best because there is no ground connection between the two units. Given the near total lack of any grounding standard in consumer audio your observation does not surprise me.   d.b.

What a crock!!!  where do you get this stuff??

Everybody knows the light is smoother, gentler, and much more refined in dealing with the lectrons and photons..

Course, that'd be only for plastic..glass is waaaay to brittle for the delicate highs..

Hey Dan, how's life treatin ya?  Hopefully well.

Cheers, John

[randytsuch]

Randy

For a cable, measure L and C and calculate Z.  it will be =sqr(L/C).

Measure L with the far end shorted.  Measure C with the far end open.


For an output or an input, put a 1K resistor in series with a sine gen into the output.  Push 1.075 volts in, to force 1 milliamp current. (close enough).  As far as I am aware, no equipment should be damaged by forcing one milliamp into an input or an output. (anyone out there differ on that?)

The voltage measured at the output or input will be the d ...

Hi John,
Thanks for the information.  I will try it as soon as I pick out and then buy my digital coax cable.
The part for measuring an cable, and a input makes sense, but I was not sure on the output.  You said it should be live, which I presume to mean turned on.  If you do that, won't the output "fight" with the signal gen, and mess up the readings?

Randy:

You are right, I don't come here often. When I do, it usually is because something on one forum spills over onto another one, and we would like to know in advance who is being a PITA.

OK, where was I........?

Cable:

I have found that lower loss ones tend to sound better. There is no hard and fast rule, because as you have discovered, it is a system. You have to take the whole system into account. And even then.......there still are no hard rules.

I once tried a $1000 microwave Gore-Tex ...

Hi Jocko,
OK, so a good braided shield will be more consistent than a foil shield, if I understand you.

And all of this cable is on rolls, so I am looking for something I can buy on a 100 foot roll, which does limit my options.

I can buy Belden 8281 on a 100' roll.  I tried to put a link here to the Belden website, 8281 page, but it did not work.

It is double shielded, 75 +/-1.5 ohms.  I can't find an +/-0.75 ohm stuff, most of the cable I have looked at does not even spec the tolerance.

Is this reasonable cable?

Randy

[AphileEarlyAdopter]

I'll bet the opto link sounds best because there is no ground connection between the two units. Given the near total lack of any grounding standard in consumer audio your observation does not surprise me.
              d.b.

Both, my player and receiver do not have a ground pin and are connected to the same balanced power conditioner. So I dont think it is the ground. It is quite possible the S/PDIF interface itself is compromised in the cheap Panasonic. I tried Acoustic Zen Silver photon, Zu Ash and generic coax cables > 1.5M. The 'glass toslink' still beats them. Very clear separation of instruments and much better ambience retrieval. I originally had a bias against toslink, but I am not that smug anymore.

[jneutron]

Hi John,
The part for measuring an cable, and a input makes sense, but I was not sure on the output. You said it should be live, which I presume to mean turned on. If you do that, won't the output "fight" with the signal gen, and mess up the readings?
Randy

Yes, the output will fight it.  That is the entire reason to test it live.  It's just like measuring the output impedance of an amplifier for damping factor, it can only be measured with the amp on.

For transmission lines, the returning reflection needs to see the same impedance so it is not again bounced to the load.  This means that the output node must move the correct amount in response to the reflection signal.  The correct amount is the same amount of "flex" the cable z has.

Cheers, John