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Disadvantages of using optical out from PC to DAC + Amp?

post #1 of 12
Thread Starter 

Hi,

 

I normally only listen using headphones at work where I am running a USB DAC (Music Streamer II) connected to a PPA. At home, I just use cheap 2.0 speakers with a line out from my motherboard. I noticed my motherboard also has optical out and possibly digital coax out as well. I have a spare DAC (Super Pri USB DAC 707) plus a spare headphone amp (PIMETA). 

 

I was thinking of getting the mid-range ASUS Xonar soundcard but if the idea is to get out of a noisy computer case, wouldn't running a digital like (optical) from my PC to the DAC + Amp combo work? Is there any reason I should add a soundcard and use the DAC from there? I figure digital is digital ...

 

Also, is there any difference between running a USB cable to the DAC versus running an optical cable?

Thanks.

post #2 of 12

In principle you should be better off with external DAC+amp. At least give it a try if you already have the gear.

There are a few differences between USB and optical/coax interfaces for your consideration:

- some DACs accept higher data rates from optical/coax than from USB

- if your USB bus is extremenly busy (for example with external disk access), you could experience data loss. Optical/coax are dedicated sound interfaces and shouldn't be susceptible to that

- using USB, data is transmitted raw, while optical/coax clocking is done by the PC - that may be more susceptible to jitter

If you'd like to know more, search the archives - these matters have been discussed here aplenty.

post #3 of 12
Quote:
Originally Posted by sygyzy View Post

Hi,

 

I normally only listen using headphones at work where I am running a USB DAC (Music Streamer II) connected to a PPA. At home, I just use cheap 2.0 speakers with a line out from my motherboard. I noticed my motherboard also has optical out and possibly digital coax out as well. I have a spare DAC (Super Pri USB DAC 707) plus a spare headphone amp (PIMETA). 

 

I was thinking of getting the mid-range ASUS Xonar sound card but if the idea is to get out of a noisy computer case, wouldn't running a digital like (optical) from my PC to the DAC + Amp combo work? Is there any reason I should add a sound card and use the DAC from there? I figure digital is digital ...

 

Also, is there any difference between running a USB cable to the DAC versus running an optical cable?
 

The Super Pro USB DAC 707 uses the same DAC chip (CS4398) as the Xonar DX/D1 ($50-$80).

So might as well use the Super Pro.

What digital outputs (USB, optical, coaxial) does your computer have?

You can get low cost "premium" USB,optical, coaxial cables from Monoprice.

post #4 of 12
Thread Starter 

My motherboard has an array of USB3 and USB2 out, Optical S/PDIF. I don't think it has Coax but I can check. I have plenty of cables so that's not a concern. I guess I just saved myself $30-80.

post #5 of 12
Quote:
Originally Posted by sygyzy View Post

My motherboard has an array of USB3 and USB2 out, Optical S/PDIF. I don't think it has Coax but I can check. I have plenty of cables so that's not a concern. I guess I just saved myself $30-80.

The coaxial output looks like a single RCA jack.

I guess try USB and optical, see which sounds better.

If you enable the S/PDIF Toslink optical output, set for PCM (basic 2-channel, for music), not DDL (Dolby Digital live, 5.1 (6.1) compressed surround sound)

post #6 of 12
Quote:
Originally Posted by PleasantSounds View Post

In principle you should be better off with external DAC+amp. At least give it a try if you already have the gear.

There are a few differences between USB and optical/coax interfaces for your consideration:

- some DACs accept higher data rates from optical/coax than from USB

- if your USB bus is extremenly busy (for example with external disk access), you could experience data loss. Optical/coax are dedicated sound interfaces and shouldn't be susceptible to that

- using USB, data is transmitted raw, while optical/coax clocking is done by the PC - that may be more susceptible to jitter

If you'd like to know more, search the archives - these matters have been discussed here aplenty.

wow didnt even know about that, thanx for the tip.

post #7 of 12
Quote:
Originally Posted by sygyzy View Post

Hi,

 

I normally only listen using headphones at work where I am running a USB DAC (Music Streamer II) connected to a PPA. At home, I just use cheap 2.0 speakers with a line out from my motherboard. I noticed my motherboard also has optical out and possibly digital coax out as well. I have a spare DAC (Super Pri USB DAC 707) plus a spare headphone amp (PIMETA). 

 

I was thinking of getting the mid-range ASUS Xonar soundcard but if the idea is to get out of a noisy computer case, wouldn't running a digital like (optical) from my PC to the DAC + Amp combo work? Is there any reason I should add a soundcard and use the DAC from there? I figure digital is digital ...

 

Also, is there any difference between running a USB cable to the DAC versus running an optical cable?

Thanks.

Maybe,  Pleasantsounds hit it on the head, but other things to consider would be how good the clock and isolation is on a dedicated sound card vs the freebie sound chip in the computer.  That is going to dictate the quality of the sound.  For casual listening though, the optical method may be just fine.  Its only when you put a better card in that you may notice a slight increase in quality.  Remember lots of what you hear will depend on how good those speakers and their internal amps are.

post #8 of 12
Quote:
Originally Posted by sygyzy View Post


I was thinking of getting the mid-range ASUS Xonar soundcard but if the idea is to get out of a noisy computer case, wouldn't running a digital like (optical) from my PC to the DAC + Amp combo work? Is there any reason I should add a soundcard and use the DAC from there? I figure digital is digital ...

 

Also, is there any difference between running a USB cable to the DAC versus running an optical cable?

Thanks.

The idea of the PC infecting your soundcard is an idea that tends to be overblown in the forums by people that don't really understand the theories behind it.  The STX has some of the best measurements of any audio source so, if there is so much noise infecting peoples cards, why doesn't it show up in the measurements? Don't get me wrong here, there is nothing wrong with going external but fully understand exactly why you are doing it.:)

 

Digital is not just digital because you have a timing component that can be corrupted or become sloppy which is jitter but that is not really the point here.

As to differences between USB and Optical, there can be differences yes because of the receiver circuitry.  If I had to choose between S/Pdif I would take Coaxial if possible.

Anyway, I would suggest testing both and using the one that sounds the best to you.  That being said, some newer DAC's have high quality USB inputs so it depends on the unit if you have one of these DAC's.  Aside from that it is really just a preference or convenience.


Edited by ROBSCIX - 8/9/12 at 11:54am
post #9 of 12
Thread Starter 

Wow you make some really compelling arguments ROBSCIX. Thanks for sharing!

post #10 of 12
Quote:
Originally Posted by ROBSCIX View Post

The idea of the PC infecting your soundcard is an idea that tends to be overblown in the forums by people that don't really understand the theories behind it.  The STX has some of the best measurements of any audio source so, if there is so much noise infecting peoples cards, why doesn't it show up in the measurements? Don't get me wrong here, there is nothing wrong with going external but fully understand exactly why you are doing it.:)

 

I agree with the above wholeheartedly.  I used a E-Mu 0404pci for years and did not feel I was getting crud coming through the card or the spdif out to an external dac when I went that route.  It was much better than any of my "sound on a cheap chip" computer audio for sure.

 

Digital is not just digital because you have a timing component that can be corrupted or become sloppy which is jitter but that is not really the point here.

As to differences between USB and Optical, there can be differences yes because of the receiver circuitry.  If I had to choose between S/Pdif I would take Coaxial if possible.

Anyway, I would suggest testing both and using the one that sounds the best to you.  That being said, some newer DAC's have high quality USB inputs so it depends on the unit if you have one of these DAC's.  Aside from that it is really just a preference or convenience.

post #11 of 12

The big thing to consider with an internal soundcard is mainly EMI which is why cards like the STX are shielded. Even still, EMI is not so much of an issue if you are connecting directly to the soundcard. Inside many cases there are problems using front panel connectors because the AC '97/HD Audio cables are rarely shielded and when they are near other components like video cards they pickup EMI.
 

post #12 of 12
Thread Starter 

I went ahead and hooked up an optical cable to my onboard SPDIF and my DAC. From there I am running it to a PIMETA. Things sound great but with SuperFi 5's, it's really noisy (static, white noise) when no music is playing, even at volume all the way down. Is this just the sensitivity of the IEM's?

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