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S/PDIF Output on Asus K8S-LA “Salmon”

7 March 2010 No Comment

Ever since I got a PlayStation 2 and found the joy of games that support Pro Logic II, I’ve had a thing for surround sound. It’s like this perverse fixation that gives me a boner every time – you haven’t played games like Need for Speed: Underground 2 or Ace Combat 5 until you’ve played them with Pro Logic II. Seriously, the effect is that dramatic.

The PS3 is even better because most games support Dolby Digital 5.1 native – the PS2 lacked the processing power to generate this signal dynamically, only pre-rendered cut-scenes had Dolby Digital.

I started out modest – an old “Paramount” Pro Logic decoder, which I eventually traded in for a Yamaha 5.1 receiver. This thing is great – it’ll fill up a huge room with modest speakers no trouble at all, and it’s been in our “great room” since we moved out here. Unfortunately, our “nice TV” broke permanently, and we shut off our satellite TV in favor of streaming NetFlix… meaning my beautiful receiver was relegated to my younger brothers in law playing PS2 on it.

This morning I decided enough of that, I’d bring it up here and use it in our bedroom. Story time over: I decided to see if I could hack digital output from my HP Pavilion a1213w desktop. I checked the motherboard, it’s an Asus K8S-LA “Salmon” board… bit of a piece of shit really, but it does the job.

S/PDIF on Asus K8S-LAIt sports a RealTek (ugh!) on-board audio with 5.1 output. Awesome – but no digital output in sight. Searching for the manual, I found an S/PDIF output on the board which requires a daughter-board to give you a coaxial/ToSLink output. Check eBay – ~$20… fffffuuuuuu that.

A quick Google search shows plenty of other folks hacking their own so I decided to give it a shot. Ratting through my box of parts, I came up with a 4-pin CD-ROM-Audio cable from years gone past and cut it apart. I also dug out an RCA cable (I went with Coaxial for the PC since my PS3 will be using the only available ToSLink socket on the receiver) and cut it up too.

S/PDIF on Asus K8S-LAA simple hack really. Pins 1+2 are ground and digital-out respectively, with the third pin being +5vdc for powering the bits for ToSLink communication… irrelevant for my purposes. I carefully cut the connector to a little larger than the three-pin connector, then used a Dremel with a sanding wheel to smooth it to a perfect three-pin shape. I pulled the unused extra wire out, since I didn’t want to accidentally short my mobo’s +5vdc. I had the black wire on the GND pin and the white on the S/PDIF pin (see diagram at left) and it was a simple matter of soldering colors to colors to connect the RCA. Route it out the back of my PC and into my receiver.

lolrealtekDigging through the RealTek control panel’s “Multi-Channel Sound Manager”, the instant I clicked “Enable Digital Output” the PCM light came on my receiver and I’m good to go. Turn off all the DSP shit the kids had turned on, and my iTunes output is so manly I need chest hair supplements to keep up.

Update: Okay so apparently my RealTek card can’t output Dolby Pro Logic II (or even anything remotely close to surround sound) over S/PDIF – PCM is it (and PCM is limited to two channels). According to a thread on Overclockers, most sound cards are limited like this… if you want surround sound in games, you’re stuck using the analog outputs and the 6ch input on my receiver.

So I scrounged up some 3.5mm to RCA cables, and hooked it up… and low and behold I have full surround on games like Left4Dead. I press the 6ch button on my remote, and I’m switching back to digital output, so I can take advantage of my receiver’s vastly superior DAC for music. Not optimal, but the best I can probably do without a heinously expensive Pro Logic II capable sound card. 🙁

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