eliminating "system noise" from PC sound output... - AVS Forum
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post #1 of 13 Old 01-23-2004, 10:50 AM - Thread Starter
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Im in the process of building a new hi-fi system to connect my HTPC to. I know that PCs inherently produce "system noise" from all the electromagnetic interferance that runs rampant inside a computer case, and that this interferance will distort the sound comming out of any computer... my question is: if i were to buy a professional grade sound card with digital optical output, and connected it to a preamp with digital optical imput, would that eliminate system noise from my computers audio output??

the way i figure it, if your using digital audio extraction from your cd-drive, then your soundcard outputs that digital signal out over an optical wire, then the digital audio data would be 100% intact with no interferance...

is this a sound theory, or will system noise distort my sound nomatter what??

this is the soundcard im looking at:

http://www.m-audio.com/index.php?do=...1d7de8f4cc2c3e
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post #2 of 13 Old 01-23-2004, 10:59 AM
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In theory if you connect optically the only PC noise that you would get in your audio would be radiated or RF noise but I doubt that your PC would put enough out at a high enough level to actually be noticeable.

If you use coax you run the risk of creating a ground loop which could lead to audible hum.

Either way, barring gross errors, you should always get 100% accurate digital data out of the sound card.

The M-audio is a nice card. You should be fine with it.
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post #3 of 13 Old 01-23-2004, 11:03 AM - Thread Starter
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ok, sweet, thats what i thought. i have another question: will the optical out be able to carry multi-channel audio? will i be able to run a dvd, and still get a true 5.1 audio stream? provided the pre-amp can decode it of course....
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post #4 of 13 Old 01-23-2004, 11:25 AM
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If you are really concerned about the effect of 'rampant system noise' than M-Audio Delta 2496 is a weak choice.

You should be looking for RME DIGI96/8 PAD or PST, or even better RME HDSP9632.

The 2nd question is the rest of your system sufficiently high-enough for the RME quality?
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post #5 of 13 Old 01-23-2004, 11:36 AM - Thread Starter
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how about any of the terratec audio solutions? ive never heard of RME....

for your second question, are you asking me what my stereo will be? im still in the process of selecting an amp and pre-amp, but the speakers will be a pair of belle klipsch horn-loaded speakers, im looking at some vintage HH Scott tube amps, and the pre-amp i have no idea about...
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post #6 of 13 Old 01-23-2004, 11:40 AM
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Check www.rme-audio.com for more info on the above cards.

Also search the forme for references to RME.

Re 2nd question, it is most likely that RME may become of higher quality that the rest of your system in which case you'll need to revesre the question and ask if the noise produced from your AV porcessor/amps/cable is reducing your audio enjoyment.
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post #7 of 13 Old 01-23-2004, 11:45 AM
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Yes, the M-audio will carry N.1 sound.

All of the digital sound cards are simply "passing thru" the S/PDIF streams for DD or DTS so issues like jitter and the quality of the DAC stage in the sound card are moot.

If you know you are only going to be using it for movies then any "decent", where decent is defined as much by its driver support as anything, sound card will be sufficient.

If you are going to be doing D/A on the card or using LPCM, where clock jitter matters, then these will be more important.
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post #8 of 13 Old 01-23-2004, 11:49 AM
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Not sure why Branxx recommended against the M-audio solutions. Can you add some details? M-audio Revolution is generally considered a pretty solid card for straight-through digital to the receiver, at least with its ASIO drivers--isn't it?

Whether your card will pass digital 5.1/6.1/7.2 totally depends on the card, not the digital output. Some of M-audio's cards support 5.1 only; others support up to 7.1. Check the specs.

If you're digital all the way through, then RF noise shouldn't matter at all. RF only matters when you get into the analog domain. I'm not sure what Branxx meant when he called the Delta a weak choice if system noise is a factor. I mean, 24/96 has a really good noise floor and S/N ratio, and if it's digital all the way through, what other kind of "noise" could be introduced? I'm not challenging, just questioning.
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post #9 of 13 Old 01-23-2004, 12:21 PM - Thread Starter
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5.1 dd/dts and the like are not really a concern right now, all i care about is regular old stereo sound out of my computer... optical out will work with just plain stereo sound right?
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post #10 of 13 Old 01-23-2004, 12:47 PM
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loraan,

I have owned and extensively experimented with M-Audio Delta 9424, M-Audio Audiophile, M-Audio Delta 410, Delta 1010, STAudio DSP24, Echo Mia, RME DIGI96/8 PAD, RME HDSP 9632, Lynx Two Model B.

I would rate Delta 9624 the weakest and I am now using it in my desktop (reading e-mail and similar activities).

NutGun would be better of buying much cheaper Revolution 7.1 or even better Prodigy 7.1 than Delta9624.

But, the main confusion is that 'the rampant noise' within the PC is somehow going to majorly influence the sound quality, as if the PC sound-card manufacturers are not aware of the operating environment for their products and did not intentionally designed it to compensate for it.

NutGun gives impression of great concern about the sound quality. That being the case RME is choice that will put the mind at rest and let him concentrate on other parts of the audio system where sound can be improved further.

For the reference I now use RME DIGI96/8 PAD connected both by analogue and digital (AES/EBU) to Lexicon MC-12B that is driving a battery of M&K active speakers, 6x2510P, 4x2525P and 2x5310 sub-woofers.

RME produces clearer and more pleasant 2-channel audio than Lexicon can from the same source. Use the correct tool and 'rampant PC noise' does not enter into equation!
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post #11 of 13 Old 01-23-2004, 12:55 PM
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Branxx,

Thanks for clarifying your results.

Based on NatGun's desire for just LPCM then I would have to agree that there can be a significant difference in the quality of the output since the effect of jitter on the clock can be audible and will indeed be impacted by system noise in the PC.

Hopefully the above comments won't trigger a jitter war.
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post #12 of 13 Old 01-23-2004, 01:43 PM
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Quote:
Originally posted by Branxx
I would rate Delta 9624 the weakest and I am now using it in my desktop (reading e-mail and similar activities).

NutGun would be better of buying much cheaper Revolution 7.1 or even better Prodigy 7.1 than Delta9624.
I only have experience with the Revo, which I'm using in my HTPC now. Could you elaborate on how the Delta is weaker? Just curious...
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post #13 of 13 Old 02-06-2004, 04:52 PM
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Since system noise in the PC does matter...

I'd recommend Epox 8rda3 series mainboard if you happened to go the AMD Barton 2500+ route.

Experimenting with TV cards I found it has cleaner pci voltage regulation to a7n8x-l which you cannot see it being mentioned in any mainboard review yet very critical for us HTPC users.

TV cards are pretty sensitive to system noise/pci voltage regulation. And your sound card will be using it too. For a side note, the AGP and DDR memory voltages are seperated from pci voltage. Each has its own regulation circuit.

Happy camping!
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