advertisement


Digital Coax

M

Mr Pig

^'- -'^
I made up a long digital coax, van den hull I think, to link my blueray player to the DAC on the other corner of the room. I only connected the screen at one end. Is that right?

By the way, I tested the cable at 12m long and it worked fine. It's now under the floor and a couple of meters shorter.
 
Digital does require a positive and return as does any electrical circuit. I am assuming that as you refer to it as coax, it is one central conductor and a screen, in which case the screen would conventionally be the return.
If you get a signal with the screen connected at only one end, short (pun intended) of a whisker or two completing the circuit, I am confused......

I have done nothing with digital cabling, but being digital, logically, quite a bit of anlaogue logic about sound quality, interference etc. does not apply. In theory...
 
Vinny said:
Digital does require a positive and return as does any electrical circuit. If you get a signal with the screen connected at only one end, short (pun intended) of a whisker or two completing the circuit, I am confused....
Click to expand...

Well, it works. The screen is only connected at one end it's 12m ling and it works. I knew it would.

Years ago I was messing around with my DAC to see what different coax connections would work. I plugged one cable into the DAC, another into the source and used them like test probes to send the signal through.... anything conductive that was lying around. The kettle, a steam iron, the ironing board, anything that was conductive worked and I didn't hear any issues or noticeable drop in quality. At no point was the screen/second conductor connected.

I can't pretend to know why but I assumed the screen was just that and conecting it at one end would be better. Happy to learn on this?
 
As above, you must have a + and - so your Coax has two wires and a screen.

The only time I use the screen is analog from turntable to amp.

I have found that I perceive better sound from unscreened in all other IC’s.

Gary
 
If it`s 75 ohm coax and you have not connected the screen at one end you are probably getting an earth return through the mains earth. This is not good practice, even though it works in this instance. Coax cables should always have the screen connected at both ends.
 
Barrymagrec said:
If it`s 75 ohm coax and you have not connected the screen at one end you are probably getting an earth return through the mains earth. This is not good practice, even though it works in this instance. Coax cables should always have the screen connected at both ends.
Click to expand...

Thank you. I'll get the soldering iron out :0)
 
Barrymagrec said:
Have you checked for shorts?
Click to expand...

Yes thank you, wearing them as we speak. And a large pair of donkey ears. As it turns out I am a larger donkey than my wife thinks I am.

When I tested the cable I neglected to unplug the optical lead I was previously using and it was THAT which I was hearing through the DAC. Oh, but it gets worse.

I plugged the coax into the back of the Blueray player just looking down the back of it and seeing the word 'output' half hidden under the socket. After testing the continuity of the coax lead, looking through the Blueray player menu to check it wasn't a setting I pulled the player out to have a closer look.

The feckin thing doesn't even HAVE a digital coax output! I was plugging the lead into the composite video output.

Sorry for wasting your time, I hope at least I've given you a chuckle.

What an idiot.
 
Just an update. I bought a blu ray player which has an actual coax output today and it works fine. The long cable is no problem.

Thank you all for your advice.
 
Long cable can be 'better' because the inevitable reflections are moved further away in time from the signal's edges. In practice probably insignificant, especially with modern SPDIF receivers.
 
Barrymagrec said:
12 metres is not really very long for a terminated coax cable, especially at the low digital audio data rate.
Click to expand...

When I first looked at this I got the impression that it was, which is why I went with an optical lead. Such a crappy connector though, keeps falling out of the DAC. Glad to see the back of it.
 
You must log in or register to reply here.


advertisement


Back
Top