SPDIF: VCC / SPDIF which way round?

[rogercameron]

I have an MSI motherboard with onboard sound. It also has an SPDIF connector to plug in a back panel socket (which can't be brought anywhere). I am trying to build the connector. There are 3 pins available for connection . Pin 1 is labelled VCC, Pin 2 SPDIF & Pin3 No Connection.

It would appear that none are GROUND.
Therefore, which of Pin 1 or 2 goes to the RCA shell / Centre? Does the shell require isolating from ground?

I have been searching everywhere but can't find the answer in simple (me) terms. Can anyone help?

[MWP]

What motherboard?

[rogercameron]

It's an MSI KM2M and needless to say, MSI have been as helpfull as a .......

[markp]

It is on the MSI site, I just saw it yesterday. They have all the pinouts for the different motherboards SPDIF.

[markp]

If found this, hope it helps:
I use this with my K7N2GM-L motherboard with the optical out. I suspect that the coax out will work too.

Get the manual for the K7N2G motherboard which uses this connector, page 2.25, to see the pinout. I used connector pins 1,3,5 (VCC +5v, spdif data-out, ground) mapping to pin 1,2,3 on the K7N2GM-L. Actually, I don't think you even need pin 5 (it is N/A on the K7N2GM-L). I looked up the Toshiba optical transmitter that is on the board and it only uses 5v, data-out, gnd.

For the connector, I used a cdrom audio cable 4 pin connector cut down to 3 pins (you may be able to find a 3 pin one). I remove the 1,3,5 wires from the above and put them in the audio connector. This then fit onto the header on the K7N2GM-L motherboard. Optical SPDIF out now works connected to my Yamaha RX-V540 surround sound A/V receiver.

The actual adaptor is available from PCClub.com for $8

[rogercameron]

Thanks. I think we're on the same wavelength, however:
Is the shell of the coax SPDIF grounded?

There can be only two connections to a RCA socket.

I am suspecting that the VCC signal (5v on page 2-25) is for the Optical circuitry of the SPDIF Jack. Is there anyway of confirming this? Long stretch this but... Can anyone disconnect the VCC connection and see if COAX still works?

My only other conclusion is that the shell of the RCA Jack must be isolated from ground and the connections used are VCC and SPDIF (SPDFO); but which way around?

It seems silly, but I'm struggling on this and trying to avoid buying another sound card.

[dhaen]

Seems like this connector is for an optical (Toslink) transmitter.
If you want to use it for a copper SPDIF connection, I suggest you connect the Vcc pin to your shield via a 100nF or similar cap. This should work.