S/PDIF out from motherboard audio, help

[werdwerdus]

I need to get the digital out from the onboard audio on one of my computers. I'm assuming I need to make a digital coaxial cable connected to the S/PDIF pins on the motherboard. Here is a picture from the motherboard manual, which pins do I use to make the coaxial cable? Also, would I be safe to mount an RCA jack on the back of the computer case for this (my instinct is telling me NO)?

My first guess would be to use SPDIF_OUT for the center conductor in the RCA cable/jack, and either GND or VCC for the ground/outer conductor. But I'm not sure which.
Thanks in advance.

 

[picklgreen]

Pin 2 would be the center conductor of the rca jack, pin 6 would be the outer. Make sure you use some decent shielded cable to go from the motherboard pins to the rca jack. Mount the jack either on the front of the case somewhere or on a blank spacer on the back (the thing you remove when you add a new card). Make sure the jack you use is isolated from the outside of your computer case. Remember digital cables are coaxial....not just some ordinary rca cable u have lieing around the house.

 

[werdwerdus]

About the coaxial cable...

Could I use the kind of coaxial cable that is used for cable television? (obviously terminated with RCA plugs) I have some of it somewhere so I wouldn't have to go out and buy something or order something. Also would an RCA cable that is meant for component video work? IIRC they are 75ohm cables. If not I'll just find or order a few feet of generic coaxial cable from markertek or something.

 

[slwiser]

The chances that you will get bit-perfect out of the digital SPDIF out of your computer is very low assuming a WinXP OS. If you are talking about an intel motherboard and a Sigma Tel chip set then you will get an fractional upsampled output to 48 khz that fails the udial audio clip test. Search for udial audio chip and you will find this.

The best thing to do is get one of those USB output devices that you fine used around there. The go from around 40 dollars US up. These will use the ASIO4all or another ASIO driver that bypass the windows kmixer (the MS sound mangler).

udial can be found here:

http://www.hydrogenaudio.org/forums/...showtopic=9772


Quote:

Originally Posted by werdwerdus /img/forum/go_quote.gif I need to get the digital out from the onboard audio on one of my computers. I'm assuming I need to make a digital coaxial cable connected to the S/PDIF pins on the motherboard. Here is a picture from the motherboard manual, which pins do I use to make the coaxial cable? Also, would I be safe to mount an RCA jack on the back of the computer case for this (my instinct is telling me NO)? My first guess would be to use SPDIF_OUT for the center conductor in the RCA cable/jack, and either GND or VCC for the ground/outer conductor. But I'm not sure which. Thanks in advance.

 

[werdwerdus]

Yeah I know all about that but this should be a nearly free "upgrade" from the analog audio out that I'm currently using on that computer. I'm just hoping to get rid of the hum that is present when a cable is plugged into it; I don't really care about getting bitperfect in the situation. I think it's a VIA Vinyl AC'97 chip or something, fwiw.

 

[slwiser]

I see you have other issues than the detailed sound problem.

Your hum issues are probably power related. You need some type of way to separate you power supplies. Focus on that and your hum will probably go away.

To bad you don't have an optical device that you can use to break the ground issue. You could go to Bestbuy or Circuitcity and purchase one of those 30 dollar USB devices that has an optical SPDIF output and see if this works for you first. Turtlebeach makes one of those I think. http://www.turtlebeach.com/site/prod...roducthome.asp

Quote:

Originally Posted by werdwerdus /img/forum/go_quote.gif Yeah I know all about that but this should be a nearly free "upgrade" from the analog audio out that I'm currently using on that computer. I'm just hoping to get rid of the hum that is present when a cable is plugged into it; I don't really care about getting bitperfect in the situation. I think it's a VIA Vinyl AC'97 chip or something, fwiw.

 

[MisterX]

Quote:

Also, would I be safe to mount an RCA jack on the back of the computer case for this (my instinct is telling me NO)?

Yes.

Quote:

Could I use the kind of coaxial cable that is used for cable television?

You sure can.

Quote:

I'm just hoping to get rid of the hum that is present when a cable is plugged into it

Do you have a cable TV feed connected to the system at any point?
(the "real" ground from the cable TV cable is a common source of ground loops in a multimedia system)

 

[werdwerdus]

Well when I unplug the cable that is connected from the computer to the receiver, the hum goes away. I think I have enough information to do what I originally planned and what my OP was asking.

Thanks for the information especially picklgreen and MisterX (for explicitly anwering my questions)

And thanks slwiser for suggesting a USB solution if I can't get the sound up to what I want out of it.

 

[picklgreen]

Any USB option will fix your problem here. You will not get any hum at all if you use a USB based sound card. You could build one (this is the DIY forum!) or post a WTB in the classified forum. People will jump to sell you a USB DAC. I currently have 3 Alien Dacs that would be perfect for you! You run the Alien out of your USB port than out of the ALien into your stereo receiver....

But my stuff isnt for sale...