Could someone clarify this (concerns HDMI/optical/sound cards)

You need to actually clarify whether you're using an ATI 4xxx or 5xxx as this will make a huge difference.

The ATI 5xxx series cards can bitstream full digital 5.1/6.1/7.1 audio to your receiver. The 4xxx cards can't.

Assuming you have an ATI 5xxx series card then it will give you better audio output then anything an optical cable can give you, as long as it's plugged in directly to your receiver. A sound card will not offer you anything unless for some reason you need analog outputs.

Well there are many reasons such as the sound card having analog outputs, inputs, extra processing capabilities in some cases, game ports, firewire, etc. The HDMI just sends audio out with a video signal and doesn't do anything else. If you need the extra features, you need the sound card, but if you're just sending audio from movies, mp3s, etc to a receiver the ATI 5xxx card is just fine.

HDMI is superior (from an ATI 5xxx) for all of the things you listed. Especially for Blu Rays because optical can't output trueHD or DTS-MA and HDMI can. This is assuming the HDMI is plugged directly into your receiver of course.

HDMI is a video interface that also does audio - a sound card isn't going to have HDMI because sound cards don't output Video.

You have to understand that the audio you are talking about is Digital. It is just a stream of ones and zeros. With HDMI, the Video card passes the audio stream, with an audio card the stream of bits is passed via SPDIF (Optical or Coax). In either case the actual stream doesn't get turned into true "audio" until your receiver decodes the stream from DTS/AC-3 to actual sound.

HDMI has the higher bandwidth capability and can pass the full HD audio that BluRay supports. If you are using SPDIF, you just don't have enough bandwidth to pass the whole HD stream and have to downgrade from the HD stream to the standard stream.

Since you are using pass-through and not actually decoding the audio on your HTPC, the HDMI solution would be best in my opinion, since you will be able to support the HD audio.

TH

What nonsense!!

All ATI video cards from the HD series can do Digital Audio. All of them without exception: the 2,3,4 & 5000 series all pass-through digital audio, the difference is in the type of digital signal. For stereo music it makes no difference whatsoever.
An optical port transmits a SPDIF signal which can also be carried over a Co-Axial connection or a HDMI connection. No difference in quality (well, there's a debate about that); theoretically it is transmitting the same SPDIF signal.
A SPDIF signal can be sent over a Co-Axial, Optical or a HDMI connection.
And SPDIF can carry 5.1/6.1/7.1 channels of (DVD quality) sound. It can also carry up to 2-ch PCM signals.

HD 2/3000 - SPDIF & 2-Ch PCM
HD 4000 - SPDIF & 8-Ch PCM
HD 5000 - SPDIF, 8-Ch PCM & bitstream HD codecs (w/PAP)

And also, there are 2 sound cards with HDMI and they pass video. [1] The Auzentech Hi-Fi Home Theater and [2] The Asus Xonar HDAV (in 3 flavors).

OP,
You are fine with your 4000 card and your Onkyo AVR (once you get it working, that is).
Since your AVR can't decode HD audio there's no point in buying a 5000 card; your 4000 can do the same job as the 5000. It is essentially the same audio chip + PAP.
And your friend is either mistaken or he's talking about a different processing route.
If you have a sound card the audio processing is done within the PC and the sound card's DACs convert the digital signal into analog and send it out. Not the best way to do it.
However in your case, you are using your AVR to do the decoding hence you are sending out the digital signal as it is without any processing being done in the PC. All the processing and conversion is being done in the AVR. An AVR's DACs will (almost) always be better than a sound card's DAC. There are notable exceptions such as the Asus Xonar Essence/Deluxe and a few others.
When all your processing is done by the AVR the quality of sound depends on the AVR; your PC has nothing to do with it.


What's the point? The Optical port is only going to send the digital signal out of the PC; can be done using Co-Axial or HDMI , whichever you already have. Why buy another card for that?

Utter nonsense!
HDMI can pass DD and more. It depends on the audio controller; if the chip can do it then the HDMI spec has enough bandwidth.


Depends on where the processing is being done. If all you are using the sound card is for sending the digital signal, then its not doing the processing, thus making it redundant.


You are right!


Again, utter nonsense. The only way you get a better sound in your PC is if your sound card has top-of-the-line DACs and your AVR is crappy.
In your case, your AVR has pretty decent electronics.

For info about HD (specifically Blu-Ray) audio on a PC read this.

To summarize in 2 lines.

A 4xxx card will pass any audio signal an optical port can.
A 5xxx card will pass any audio signal an optical port can plus higher quality audio formats the optical port can not.


Now, having said that, it appears your receiver doesn't do the high def audio formats. I believe you could put in a sound card and get 7.1 analog output that would sound better than Dolby Digital or DTS assuming you decode from a HD audio source (Bluray playback basically).

Peter

No, a 4xxx card can pass 'higher quality' audio signals a.la. multichannel PCM.
What it cannot pass are the HD audio codecs due to lack of PAP. Bandwidth is not the problem, PAP is. If PAP wasn't a requirement, then the 4000 cards have enough bandwidth to pass the HD codecs too.

Not exactly certain what he's talking about and where he's obtaining his information. What is a '3 channel signal'?
Bitstreaming means sending the signal out of the PC as it is without any modification. Read the link on 'HD audio in a PC'.

You simply need to install the latest drivers and configure 'Playback Devices' in Windows. It simply works (well there might be other problems but not because of this).

Get a 5:1 switch from Monoprice and connect all your devices to that switch and connect the output of that switch to one HDMI input on your AVR. Leave you AVR on that input for all time and switch inputs using the 5:1's remote control.

Intel HD Audio HDMI is noisier than X-Fi DSP S/PDIF to the same AVR. So presumably Realtek HD Audio HDMI is similar (also, Realtek HD Audio S/PDIF is not on par with X-Fi's). So digital is not all the same even when bitstreaming, let alone actually rendering. However, for mere bitstreaming purposes the difference is probably not noticeable -especially with speakers rather than good headphones.

One digital signal is better than another? Unless I'm mistaken, the audio stream is pulled out of the source material and passed intact to the final sound processor (in this case the receiver). There is NO processing of the signal other than pulling the audio stream out of the source, no conversion, any difference in the perceived signal quality would be due to the receiver processing HDMI slightly differently than SPDIF. The card on the PC is really irrelevant, as it is only being used to pass the signal, it doesn't process anything.

If you are using the card to Decode the audio, say to listen on Headphones, then the quality would matter.

TH

There's been some discussions and hot debates about this topic: Noise in Digital signals. Lets leave that for another forum/thread.
The original topic under discussion here was the signal transmission capability of different ports, not the signal quality itself (even though OP phrased it that way).

Thank you for this pithy, informative reply. I've been reading hundreds of threads and articles trying to understand how to best pass through sound from my PC to receiver and just getting more and more confused. Your post cut right to the chase.

My major interest is my music library on the server streamed to my high-end receiver, secondary is streaming movies. Want the best quality sound and my receiver to do all the work. Have a 8600GT hooked up to an older hdtv via component and xplosion sound card via digital to receiver. Just bought a new TV and want to hook it up via HDMI to the PC. Welcome to PC hell trying to figure this out...older HDMI video cards that pass video only...new nvidia cards that need to be hooked up to a soundcard by a cable, but wont pass through blu-ray sound...ATI 4000 vs 5000 series. Xonar. 12 vs 16 vs 24 bit. 44 vs 48 vs 98 kHz. Disable onboard realtek chip...watch out for kmixer.

Holy mother of God. I just want to listen to my music! Pleeeeeeeeeeeeeeeease.


There I feel better now. Thank you for your post.

To narrow it down the 5450 card should be your best bet.

Thank you. Available for 100 dollars less than a xonar HDAV. Will replace my 8600 and x-plosion with one.

Unfortunately I see some posters disagree with the post that I thought finally brought me enlightenment. All digital pass through not created equal...great. But is this real? Something audiophiles could detect in blind tests?

I'm still confused about pass through. Windows must be resampling the audio right? For example, if you are playing the music in media player, the software equalizer works, so the PC is not actually sending the original unadulterated feed to the receiver?

Another very good post that is unusually clear.

Here is a good excerpt from the link that was posted.

There are three ways to get audio from a PC to a receiver;
[1] Software player completely decodes the encoded audio signal and sends it out over the analog ports, which you can then connect to the Multi-Channel input on a receiver/amp.
[2] Software player decodes the encoded audio signal to PCM (kinda like unzipping) and sends it over HDMI to your receiver.
[3] Software player passes the audio signal through without any modification to the receiver.

The 5450 card is very good with number 3 because this series of card can bitstream TrueHD sound for Bluray movies. Most cards cannot do this.

I have an Abit IP35 Pro motherboard. As best I can tell, it is not compatible with PCIe 2.1 video cards which a lot of the ATI Radeon 5xxx series are including the 5400. If so, which video card would be the best alternative for replacing a 8600GT card and x-plosion soundcard with a single HDMI pass-through solution? Probably will not be passing through Blu-ray audio, but futureproofing is always nice. Would prefer not to upgrade motherboard, strictly to avoid the hassle...plus would be tempted to upgrade from a Q6600.

edit: on Newegg I see some of the ATI 5xxx series are listed as PCIe2.0, which should be compatible. But at least one poster said his supposed 2.0 card was 2.1 and didnt work with his motherboard.

Option 3 is what I want to do but I'm fuzzy on the actual mechanics. If one is passing through sound to let their receiver to the work they'll want unadulaterated audio from the PC. But if you are passing the audio through from media center or media player, then the software volume control, equalizer etc alter the sound output on the receiver suggesting the PC is NOT passing unadulterated sound. As I said I don't quite "get" the mechanics and may be misunderstanding something.