# Signal quality from PC to Pre-Amp? For the Experts



## Panny82 (Nov 28, 2007)

I am wondering what the cleanest way to hook my PC up to my Sunfire Theater Grand II Pre-Amp. I understand you want to get the signal as least decoded as possable to the pre-amp. You want the pre-amp to do all the decoding considering it is better at it. I am just wondering the best way to do that. I am guessing when it is coming from my Sound Audagey sound card it is getting decoded some if not all then sent to my pre-amp. I have a Optical out on my motherboard but that to is tied into my sound card. To keep it short what is the cleanest and best way to send the signal so I am not loosing anything.


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## Otto (May 18, 2006)

Send the optical output from your PC to your preamp. I have been doing this for years with excellent luck, and sound quality is indistinguishable from the original CD (when sent from CD player to preamp. Of course, it should be indistinguishable from the original when sent digitally, so no surprise there. Be sure to go through all the settings on the sound card's drivers/control software. It seems like there are always a bunch of cheesy surround modes, and it's possible that one might be on for some weird reason -- set everything to "pass through S/PDIF" or whatever it's called on your system, and you should be good. 

Good luck!


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## Panny82 (Nov 28, 2007)

Is a Motherboard sound optical out as good as a optical out on a sound card? Is there any difference considering the sound card is not doing any decoding.


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## Otto (May 18, 2006)

They should be exactly the same. In both cases, neither the sound card nor the motherboard is doing any decoding (at least not in the digital to analog conversion sense). Either one will simply take digital audio samples and pass them to your receiver. 

I think your concern about audio quality is about the question of digital to analog conversion. I will generally offer that a receiver or a preamp will do a better job of digital to analog conversion than a PC soundcard or on-board audio. I might describe the analog signal as more "fragile" than the digital -- it's more prone to noise and interference than the digital samples. Therefore, when the analog signal is handled in the very noisy environment of the computer, it might pick up noise. Also, most soundcards and such are relatively cheap, and use cheap components to handle the analog signal after the conversion. This again leads to noise in your audio. I have a PC connected to a receiver in my office on an analog output and if I turn the receiver up all the way with no audio playing from the PC, there will a very high noise floor (a lot of hiss coming from the speakers). If I do the same thing with a good analog source (e.g., even a cheap CD player), there's very little noise floor. 

Your Sunfire will definitely do a better job decoding the signal. Hook either the soundcard or the motherboard optical out to it and go for it! Actually, hook them both up and switch back and forth. You should not be able to hear a difference. If you can, I'd think that there is something wrong in the soundcard settings or drivers. You can also compare it to the analog output and see if you can hear a difference. 

Of course, there are high end sound cards that have been engineered to avoid the problems I discuss above. But, chances are that unless you've specifically searched out such a high end sound card, you have a cheapy model, and the above discussion applies. 

Also -- all this "which sounds better" discussion is dependent on your ears and the resolution of the rest of your system. 

Good luck!


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## Pinhead-227 (Dec 24, 2008)

I completely agree with Otto. Another thing to consider is that PC sound cards usually have subsonic filters built-in which will filter out a lot of the signal below 40 Hz. For most of us crazy HT guys, 40Hz is just the _beginning_ of bass.  With the digital output you don't have to worry about any kind of filtering unless your drivers and/or settings are to blame. 

I first ran analog out on my PC and was impressed (went from PC speakers to HT receiver and pro speaker system). It was even a bigger step up, though, when I went from analog to digital between the PC and the receiver.


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## Panny82 (Nov 28, 2007)

Thanks for all your help you put it all in perspective for me in a way i could understand. 

Thanks
Mike


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## Otto (May 18, 2006)

No problem! Let us know how it turns out.


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## erasma (Apr 18, 2009)

Remember that Fiber does not get any EMI like cable does - So for your application Optical - also is your pc's get hit by lightning or anything like that your amp is safe!

Some PC cards, really do good DAC work & should not always be seen as a none audio piece of equipment.

The Asus Xonar 1.3 Delux card is really worth looking at for HTPC applications


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