PC motherboard SPDIF header connection

[keiths]

Hi All,

I'm about to replace my ancient HP tower that I use as my music streamer. This is currently running XBMC, but would like to move to something quieter, smaller and leaner. I have a mini-itx dual-core Intel Atom board on the way that I picked up cheaply second hand together with 1GB DDR-3 RAM. I have a 16GB SSD left over from another project and intend to case these up in a small fanless case with a pico psu and external power brick. I'll then use Voyage MPD to stream (music files stored on my existing Linux server) to my Caiman DAC. The PC will be headless with control via MPDroid Android client (initially on my phone, but if this all works well I intend to get a cheap Android tablet).

The motherboard in question has a standard 3-pin SPDIF out header with the pins labelled GND/SPDIF/+5V. I've had a search around and have seen reference to simply connecting a BNC socket to the SPDIF and GND header pins - I guess the +5V would only be needed to provide power for TOSLINK? Anyone know if this is correct and it is that simple - add an insulated 75 ohm BNC socket to the back of the case and wire it up?

Would adding a pulse transformer be a good idea? - if so where do I get one (or is it a case of winding my own - if so what bits do I need to buy and how do I wind it?)

Cheers

[NRG]

Depends on what is already on the motherboard, however, yes a Pulse TX is a good idea with some notional 75 Ohm termination.

IE:

Without a TDR you can only guess at what the correct termination will be but its better than nothing!

Edit:

For a Pulse TX you need something like a Murata 76601/3c, get something with similar specs.

[NRG]

A good web page with some ideas on output circuits:

http://www.epanorama.net/documents/audio/spdif.html

[keiths]

Many thanks for that Neal.

[wobbleu]

I've wired a phono socket up to the two spdif pins on 3 or 4 PCs and it's always worked fine for me - certainly no noticeable noise/interference.

Currently using that option with a dual-core atom motherboard into my Rega Dac and I'd say there's no difference sound wise between that and the coax out from my squeezebox into the same Dac on the other COAX in port.

I just cut through an old IC cable and soldered it to a 2 pin motherboard connector and covered the join with heat-shrink tubing.

Chris