You can see the SPDIF In connector present on some GeForce video cards in Figure 5.

click to enlarge
Figure 5: Detail of the SPDIF In connector on a GeForce 9800 GT.

In order to use this connector you will need two things, a small cable, which will be used to connect the SPDIF out connector from your sound card or motherboard to the video card, and a DVI-to-HDMI adapter, to convert one of the DVI connectors from your sound card into HDMI.

click to enlarge
Figure 6: What you will need.

First you need to locate on your motherboard or sound card a connector called “SPDIF Out” or similar, see Figure 7.

click to enlarge
Figure 7: SPDIF out connector on a motherboard.

Then connect the cable. The cable has two wire, one black (ground) and another with a different color (red in our case), which is used to transmit SPDIF data. You connect each wire to the corresponding pin. This information can be seen on the board manual or at the board itself. If you pay close attention to the connector in Figure 7 you will see that pin 1 is labeled “VCC,” pin 2 is labeled “SPDO” (which means “SPDIF Out”) and pin 3 is labeled “GND.” So in our case we need to connect the red wire to pin 2 and the black wire to pin 3. Pay attention because the meaning of each pin can vary according to the board.

click to enlarge
Figure 8: Cable correctly connected to the SPDIF out connector on the motherboard.

The next step is simple: connect the other end of the cable on the video card and your system will be sending digital audio to the HDMI connector.

click to enlarge
Figure 9: Cabled correctly connected to the SPDIF in connector on the video card.