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PC audio cards to Processor

Hello, my question is probably out of the scope of this forum but I will ask any way.
I have decent audio system Mcintosh amps, processor Magico speakers etc.  The system is used for three purposes, home theater movies, stereo music and surround sound PC video games.  I connect the PC audio card to the processor via optical out from the audio card.  In order to get 5.1 surrond I have to set the audio card to 2 channel output even though it is a 5.1/7.1 Dolby DTS card.  If the audio cards software is  set to 5.1 etc. the result is stereo where only two channels received by the processor and converted to stereo on the system.  My question is this, does the processor convert the non Dolby non DTS two channel signal into dolby 5.1 surround.  In other words if I am using a quality PC audio card that is not Dolby and or DTS cabable and is two channel only (made for headphones) does the Dolby DTS enabled processor in this case a Mcintosh convert that two channel signal into the 5.1 surround signal?  

One other question:
Can anyone recommend the best internal PC audio card for 5.1  home theater use?  When PC audio cards are reviewed its almost always for use with headphones and not for componet (processor multiple amps mulitiple subs) driven home theater systems.

Thank you.
Guy
guyt
guyt OP
57 posts
 
yes windows 10 thanks
erik_squires
16,497 posts
 
I also want to point out, you may wish to go this way:

Nvidia --> McIntosh --> TV

as this will let the Mc decode your audio directly. The other way:

Nvidia --> TV --> (via ARC) --> McIntosh


may work, but you have to use the right ARC port, and it’s iffy. If you already have it working though, you should be all set.
auxinput
2,920 posts
 
If the audio cards software is set to 5.1 etc. the result is stereo where only two channels received by the processor and converted to stereo on the system.

I have experienced this same thing when viewing sources that send Dolby Digital Plus, such as streaming sources like Netflix. On some streaming devices, it doesn’t properly convert this to "normal old Dolby Digital" over s/pdif (i.e. toslink). The result is only 2 channels of the 5.1 being decoded and played by the processor. In my system, I HAVE to play Netflix over HDMI because that’s the only way the processor will properly receive and decode the Dolby Digital Plus signal. That being said, old school Dolby Digital and DTS is always compromised when sent over HDMI. You end up losing dynamic range and naturalness of the sound. The only thing HDMI is good for is the high resolution bluray audio formats (DTS-MA and Dolby TrueHD).

This could be a characteristic with your software or your device driver level or something else entirely. I don’t know what configurability you have currently, but see if there is a way you can configure your system to output 5.1 PCM over the spdif output instead of compressed DD/DTS. This is more supportable to processors sometimes.

As far as S/PDIF cards, the best one that is readily available now is the Asus Xonar Essence. It came in a few models (ST, STX and STX II). They all have an excellent RCA digital COAX output that also supports Dolby Digital and DTS. Drivers are available for download in Asus website and all support up to Windows 10 64-bit. The card is kind of overkill just for an spdif output because it’s costly and it’s also a full analog audio sound card, but there really isn’t anything else better. You can always find a used STX model on ebay for $50-100. If you can find a Musiland Digital Times PCI card, that’s a better spdif output, but they do not appear to be available anymore.

I cannot tell if the Xonar Essence will solve your dolby digital problem because I do not have direct experience. I can only advise on the best spdif computer card.
guyt OP
57 posts
 
That is the card that is currently installed, Asus Xoner Essence STXII. The reason I am asking about this stuff because I will have a new gaming machine built, when Nvidia starts using HDMI 2.1.  The PC builder uses Sound Blaster cards, I don't like them.  I have been setting the Asus card to dolby digital live on two channel with the A/V processor set to game dolby etc and it works, all amps subwoofers are needling. I tried what you suggested by going  into the Asus control panel and switched it from Dolby live to PCM and changed from two channel  to six channel and maxed out the sampling rate.  The result was noticeable it really woke up the speakers.  I switched in to 6 channel from two channel thinking that was appropriate because I have two fronts , center, two surround and two subs.   Thanks, your advice  improved the sound.
auxinput
2,920 posts
 
Great!  However, I would recommend setting your sampling rate to 48khz because SPDIF really cannot transfer 6 PCM channels at 96 or 192 khz.  Also, Dolby Digital / DTS would be a compressed version of 48khz anyways.  This way, you can ensure that you're getting the maximum capable bandwidth of spdif and keep full support of your McIntosh processor.

If, at any time, you want to listen to some 2-channel hi res 24/96 or 24/192 songs, you can always manually go into Asus control panel and switch it back to 2-channel PCM at 192.  But for gaming and movies, 48khz will be excellent anyways.

For the future gaming machine, unless the system or games will generate the hi-res bluray audio formats (DTS-MA and Dolby TrueHD), you are still better off keeping the Asus Xonar for digital COAX s/pdif audio output.  Hmmm, maybe setup two input configurations on your McIntosh.  On input that uses HDMI + digital COAX for audio, and a second input configuration that uses HDMI for both audio/video.
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