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Easy Question? Computer > DAC SPDIF vs USB

post #1 of 7
Thread Starter 

This may be a 'dumb' question but I can't seem to find an answer for it, should be quick answers so thanks for the help!

 

I'm trying to make DAC plans - my PC motherboard has SPDIF built in (optical & coax). Does any sort of 'processing' go on in my motherboard on the data that travels through that cord? Can I 'trust' that my DAC will be receiving a quality signal? I was briefly considering only purchasing a new headphone amp and just using the line out of my Xonar for a DAC, but I've heard PC power is dirty, so I'm thinking of getting a DAC now but trying to understand the options for computer connection.

 

Is SPDIF hit or miss based on the quality of the port, or is the fact that it transmits digitally make the quality consistent on most ports? Would a more reliable solution to be to get a USB DAC?  Since both USB & SPDIF transmit 1s and 0s I thought it wouldn't matter which you choose?

 

I'm sure there's a certain amount of debate on that issue and that's OK, but I need to hear some of the arguments and basic positions.  

 

Thanks

post #2 of 7

I have tried both and I honestly can't tell a different...at least not with my setup. There are other topics that have debated it, but the most I could come up with is that sometimes you get more sampling rates available with SPDIF vs. USB. It's a whole new can of worms trying to figure out whether or not upsampling makes a difference so I won't even get into that. I use SPDIF from my motherboard, but I can't tell the difference. I just use it because more sampling rates are available...and just in the slight case that there may actually be a difference in sound quality.

post #3 of 7

If you have a Xonar sound card already, using S/PDIF to an external DAC would be preferable from a gaming DSP effect standpoint.

 

It's still possible to use a USB DAC and not lose access to features like Dolby Headphone, but you still have to leave the sound card as the primary audio device and set the Stereo Mix input to play back through the USB DAC in the Windows sound control panel. This can add a bit of latency.

post #4 of 7

Mostly, USB or S/PDIF doesn't really matter.  Some devices handle one or the other slightly better (according to bench tests with very expensive audio analyzers, not necessarily anything of note that would hold up in listening) and furthermore sometimes don't even support 24-bit or higher than 48 kHz over USB (not that either are necessarily important).  As for what modes are supported, that depends on the USB receiver chip and drivers.

 

Unless both sides of the S/PDIF link are really incompetent, there really shouldn't be any issues.  It's slightly more complicated than just getting the 1s and 0s across, since on many S/PDIF implementations the data signal is used to clock the DAC output, so the integrity of the signal (and not just whether it's good enough to decode into the correct 1s and 0s) matters slightly.  Again, it's probably not a big deal.

 

 

If you have an Essence STX there's really no need to bother with another DAC though, unless you're sure it's having issues (dropouts, background noise, whatever).  Power all around a computer is varying sorts of dirty, but a decent sound card can filter most of it out, definitely by the time it hits its DAC output.  If what's left is audible and bothersome, then use something else.  Otherwise, what you have is something that probably outperforms the majority of boutique audiophile gear of questionable design (most of it).

post #5 of 7
Quote:
Originally Posted by Riggaberto View Post

I'm trying to make DAC plans - my PC motherboard has SPDIF built in (optical & coax). Does any sort of 'processing' go on in my motherboard on the data that travels through that cord? Can I 'trust' that my DAC will be receiving a quality signal? I was briefly considering only purchasing a new headphone amp and just using the line out of my Xonar for a DAC, but I've heard PC power is dirty, so I'm thinking of getting a DAC now but trying to understand the options for computer connection.

 

Is SPDIF hit or miss based on the quality of the port, or is the fact that it transmits digitally make the quality consistent on most ports? Would a more reliable solution to be to get a USB DAC?  Since both USB & SPDIF transmit 1s and 0s I thought it wouldn't matter which you choose?

 

I'm sure there's a certain amount of debate on that issue and that's OK, but I need to hear some of the arguments and basic positions.  

The guys over at Schiit recommend for digital out, coaxial>optical>USB.

If you use the S/PDIF coaxial (or optical) output from the Essence STX, you can still use the STX's headphone surround sound.

 

A external USB-S/PDIF converter device seems to be a good way of taking quality digital audio out of the computer and into an external DAC.

 

Why not just use the Essence STX's headphone out to drive headphones?

post #6 of 7
Thread Starter 
Quote:
Originally Posted by PurpleAngel View Post

Why not just use the Essence STX's headphone out to drive headphones?

I have LCD-2's and I don't feel like their full capabilities are unlocked from the headphone out.  In addition to that I'm getting some distortion - I do concede some of the mastering on a lot of music might just be bad and exposed. I'll be able to compare and contrast now. Luckily we're all nerds and buy and sell this stuff all the time so I'm sure I can get rid of things I don't find to be useful :)

post #7 of 7
Quote:
Originally Posted by Riggaberto View Post

I have LCD-2's and I don't feel like their full capabilities are unlocked from the headphone out.  In addition to that I'm getting some distortion - I do concede some of the mastering on a lot of music might just be bad and exposed. I'll be able to compare and contrast now. Luckily we're all nerds and buy and sell this stuff all the time so I'm sure I can get rid of things I don't find to be useful :)

The LCD-2 are 60-ohms and the Essence STX headphone jack has a 10-Ohm impedance, which might have a negative effect on headphones below 80-Ohms.

 

One option to try is to replace the op-amps on the STX, I like the AD797BRs, the LME49990 seem to be well liked.

AD797BR pre-soldered op-amps, $15 each (need 3), shipping for 3 $4.20, seller audjade_chn on eBay.

LME49990 pre-sodered op-amps, $18 each (need 3), shipping for 3 $6.00, seller frugalephile, on eBay.

So for around $60, you might change the STX's audio to more of your liking.

 

Or just get an external headphone amplifier to connect to the Essence STX's RCA outputs, 2-channel stereo audio, no headphone surround sound from RCA outputs.

If adding the external headphone amplifier is not enough, you can always get an external DAC with coaxial input.

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