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Output audio over Coaxial to AV receiver advice

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January 6, 2010 8:32:48 AM

Hi,

I am a complete novice when it comes to sound cards so bare with me if any of this doesn't make sense but here goes.

I have an AV receiver that can handle Dolby Digital and DTS sound but at the moment I have a 3.5mm cable to 2 RCA connectors to transmit the sound from my PC to the AV receiver. My motherboard is a bog standard one that doesnt have any digital audio outputs and only has 3 audio outputs on the back: the line out, line in and microphone.

As I have a spare Coaxial connection on my AV receiver what I'd like to do is purchase a PC sound card which has a Coax output so I can send the digital audio signal from DVDs and games to the AV receiver.

From what I've read on here I think that means all I need is a basic sound card that doesn't need to decode the audio signal as the AV receiver can handle that, but to simply pass on the audio signal over the coaxial cable (although it will need to be able to understand Dolby Digital). Is this correct?

I've seen a basic sound card here which is the ProSound 7.1 at Maplins so would this be suitable for my needs?

http://www.maplin.co.uk/Module.aspx?ModuleNo=226543&C=Froogle&U=226543&T=Module


Any advice is much appreciated
January 6, 2010 10:47:34 AM

It doesn't look like that card will do what you want. To get the surround sound from PC games to your receiver through its digital input, your card has to be able to encode the game audio before it sends it out. DVDs, CDs, and the like are already in digital format, and that signal can be sent straight through to the digital out, but games are behind the times in that respect.

There are two formats for digital encoding of game audio, Dolby Digital Live (DDL) and DTS Connect. Each has its fanboy contingent, but I'll bet the sound isn't a lot different. You want a card whose specifications include one of these formats. Don't let the marketers confuse you. You'll see the words "Dolby" and "DTS" all over the place, but only some of them will be what you want. It's got to be "Dolby Digital Live" (or "DDL") or "DTS Connect" verbatim. A plain "Dolby Digital" or "DTS" is not what you want; they are straight digital audio formats (actually what your card will send to the receiver after it's done encoding, but they never mention that).

The conversion happens in software, and the signal suffers some compression, so it loads your system a tad and the sound is ever-so-slightly degraded. (Also, your receiver has to be able to decode whichever format the card sends it, of course.) To get the maximum pristine goodness of game audio, you can't beat just jacking the line outs to the receiver (if it has enough inputs). But I'm presently in the process of doing exactly what you're doing, if only to minimize the spaghetti, but I'm using optical out, so I can't point you to the card you want.
January 6, 2010 11:32:17 AM

Hi, thanks for replying.

Ok that makes sense about the games needing to be encoded into digital before they are sent to the AV receiver, to be honest I'm not too bothered about games its more to do with watching DVDs and maybe Blu rays if i buy a new drive in the next few months.

I've checked my receiver and it has a 6 Channel input section, so if I were to buy that sound card could I then connect it to the receiver using the line outs, and having both 5.1 sound when watching a DVD using the Coax connection and having 5.1 sound when playing games using the line out connections?

I know this would have a load of extra cables but I dont mind that
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January 6, 2010 1:04:29 PM

Yes, it looks OK for that. My only concern is getting good drivers for a no-name card. I couldn't find a manufacturer online. The "Help/FAQs" link on the page you link to reveals that it doesn't do Vista64 or Windows7. Also, you'd have to manually switch between S/PDIF and analog.
January 6, 2010 1:16:17 PM

Would it just be easier for me to connect using the line outs to the 6 channel input on the receiver and not worry about getting a card with coax output?

I'm assuming that although I wouldnt be receiving Dolby Digital or DTS the 6 analog cables would provide me with 5.1 surround sound when playing DVDs? And then I wouldn't need to worry about manualy switching between S/PDIF and analog outputs. That also then expand my choice of cards as I wouldnt require one with a coax output.
January 6, 2010 2:14:48 PM

Thanks both for your help with this, so if i understand correctly my options are this:

1) Go for the cheap option and get a card without digital output, connect this to my 6 channel inputs on my av receiver and receive 5.1 sound but not in DD or DTS quality
2) Go for the intermediate option of getting a card with coax out to pass DVD sound in DD 5.1 or DTS 5.1, and also connect the card using the line outs for playing games in 5.1
3) The more expensive option of getting a card with coax output that supports DD Live or DTS connect, so I can have both games and DVDs in 5.1 digital sound.

If i went for option 3 would my AV receiver need to support this DD Live or DTS connect audio formats, or do these cards output the sound in a standard DD or DTS format that my av receiver could understand?
January 6, 2010 2:40:13 PM

chopkins said:


...

3) The more expensive option of getting a card with coax output that supports DD Live or DTS connect, so I can have both games and DVDs in 5.1 digital sound.

If i went for option 3 would my AV receiver need to support this DD Live or DTS connect audio formats, or do these cards output the sound in a standard DD or DTS format that my av receiver could understand?


DDL and DTS Direct are names for the encoding thingies. They output standard Dolby Digital or DTS. It's what they do and why they're needed.
January 6, 2010 5:11:45 PM

My AV receiver is a Philips FR984 but it doesn't have any HDMI input connections as its a few years old now so I don't think option 4 is possible at this point.

Option 3 is my preferred option but trying to find a sound card with coax out is a bit of a challenge as most seem to have an optical SPDIF connection, do you know of any good ones around at the moment?
January 6, 2010 6:14:07 PM

Coaxial and optical are the two forms of SPDIF. Sometimes the optical is inside the coaxial jack, so the same hole serves both forms, but if the hole won't take an RCA plug, it ain't coaxial. The bgear that our friend BDDazza linked to is only optical. The ASUS Xonar D1 is also optical only (inside the mic jack??!). You have to look at the photos and try to find a female RCA jack on it to be sure it's coaxial. Then you have to read the specs minutely to be sure that that's what it is, and for the encoding you need. Sometimes the specs at Newegg are sketchy, so you can click on "Manufacturer Product Page" in the "Manufacturer Info" tab. Let us know how you make out with that, and run your choice(s) by us here before you buy.
January 6, 2010 10:12:28 PM

Yeah, I didn't check to see whether that was one of the ones you had already linked. I figured it wouldn't hurt to repeat. I was licking my lips over the Forte, too.
January 7, 2010 9:44:34 AM

Thanks for the advice on all of those cards, I think I'm going to go for the AUZEN AZT-XPCINE 7.1 as its got both the optical and coax connectors, and I plan on upgrading my AV receiver at some point this year so I'll be able to hock it up no matter which one i get!

once again thanks for all your advice, was extremly helpful
January 7, 2010 12:06:31 PM

Does your receiver have hdmi ? Best option right now is use hdmi output from ati hd5xxx as it can transfer also non-encoded 7.1 sound to receiver (as long as receiver understand format.)

Optical and "coax" doesnt have bandwith for more then stereo in non-encoded format.
!