What's this about a 'receiver' ? Does that just mean your headphones or your own head or something?
http://en.wikipedia.org/wiki/AV_receiver
In the 80's I was an audio HiFi engineer. I have forgotten much but, still have a modicum of common sense.
Putting an amplifier or AV receiver on to your sound card is obviously going to be much better than those crappy little computer speakers. I've had a Yamaha RX-V595aRDS attached to my system for over 10 years now.
The system still sounds as good as when I first bought it but, it won't be. Capacitors age and with that comes degradation. The old Leak amplifiers used to fall out of the RIAA curve in 3 years. The only solution was to change all the capacitors. Modern amps are much better than that but, I digress.
I use optical for my output. This is provided by my on-board Realtek ALC889. Theoretically it shouldn't matter if you use coaxial or optical for your digital output. In practice you can't tell the difference, but there is a major one, the wire and plug. From what I remember there is a 3db loss over every junction, plug or socket. Also wire can pick up background noise from the mains or other equipment. Even if the plugs are gold plated it is still possible to pick up noise on the connections with movement of the plug in the socket.
When I explained to the NAD salesman what I was trying to do, he mentioned the "clock" on the mobo or card (b/c it has a sound processor) would not be as accurate as on a digital amplifier and would introduce (jitter, I believe) imperfections into the sound.
There is just so much wrong with that. How would the clock not be as accurate? The clocks you are talking about are spot on frequency, whether on your mobo, card or "Digital amplifier". They do not alter or jitter, I'm afraid that's just bollocks.
Never rely on a salesman's word. Go and get professional or expert advice.
As well as the on-board Realtek ALC889 I also have installed a second sound card. This is a Soundblaster X-Fi Extreme. I really cannot tell the difference in sound quality through an optical connection from either card.
Most sound cards (including on-board) sample at up to 48KHz. Audio sampling is usually done at 44.1KHz for CDs and 48KHz for DAT. If you want to sample at a higher rate you will need a sound card that samples at a higher rate. Some sound cards will sample at 96KHz or above, so you need to choose carefully. Some mobos don't support on board digital output but, this can be achieved by connecting a coaxial cable to your motherboards SPDIF (Sony Philips Digital Interface).
A sound card might be for you if you have specific needs. Optical in and out. Higher frequency sampling. Multichannel recording. MIDI interface.
In general, I would say your on board sound is perfectly adequate if using a HiFi system. Even better if using digital out. And yes, the headphones will sound much better through your HiFi than through the sound cards on board amplifier.
I have tried not to go in for too much detail because there is a lot to cover in sound. What I have tried to put across is just some of the basics.
Terry
