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USB vs Digital output vs USB + adapter, any SQ different ?

post #1 of 15
12/7/08 at 6:32am
Thread Starter 
So
I know this question arise from time to time, and yes I have used the search function, but still haven't found the answers I am looking to.

If you have a DAC, and you are using your PC as the source (playing FLAC files with foobar2000), and you have very good cables (if you think that matter)

What will give you a better SQ?
The digital output (COAX) of your sound card ?
Or the USB ?
Or a USB with a converter to SPDIF ? (like the one Bell Cento made or Empirical Audio or any other)
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post #2 of 15
12/7/08 at 6:54am
My vote goes to USB.
Since it can convert directly to I2S, without an intermediate S/PDIF conversion. Which should give it an edge over coaxial and optical. /me think.
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post #3 of 15
12/7/08 at 6:56am
Thread Starter 
Ok, but I want more than just "I think this or I think that"
I want something more "proved"
(not that I have anything against what you have said, but I want more)
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post #4 of 15
12/7/08 at 6:56am
You didn't find answers because I don't think an answer exists!
It all depends on how much you are willing to spend, and what the rest of your system is.
Unless you have a quite good system, the digital output of your sound card is fine. USB output depends on the device you output to, and its USB implementation.
Generally, what should be avoided is to use a device powered by the same USB bus that is used to transfer the audio.

edit: just saw the "proved" bit: you're asking for something impossible! If you want definite results, buy stuff and compare them in your system.

edit 2: re-reading my answer, I do realize it's not very helpful - sorry about that! But it all depends on the implementation. The data gotta leave the computer in some way, and USB is (in the best case scenario) better than an integrated sound card, but from there, it depends on the device.
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post #5 of 15
12/7/08 at 7:19am
Quote:
Originally Posted by HeadLover View Post
Ok, but I want more than just "I think this or I think that"
I want something more "proved"
Then you will have a hard time waiting for answers.
Cause there are no definitive answer, since there are too many variable factors. Especially the USB and/or coax implementation, both on the sender (transporter) and the receiver (DAC) end.

Its also the fact that audio quality is subjective, and hence there are no set standard of what is great, mediocre, bad and such.
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post #6 of 15
12/7/08 at 7:32am
Thread Starter 
Amm, but you know, I wonder what gives at the end of the line a more bit perfect and more quality for the DAC.

Lets assume that for all purpose we are using same DAC, same cables, same PC and so on.

And a very good PSU for the PC, and a USB ports, and a good Sound card.
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post #7 of 15
12/7/08 at 7:55am
It doesn't work like that - it's not like a "line out" you feed to the DAC, like an analog signal.
The DAC gets fed with a digital signal, and the quality of the signal depends also on the digital interface implementation of the DAC, the DAC clock, etc etc.
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post #8 of 15
12/7/08 at 8:32am
The best is whichever sounds best to your ears. And that's all that matters.

Sure, there's a 'peace of mind' that comes with knowing that you are using the 'absolute' best but does it matter if you yourself can't hear a difference?
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post #9 of 15
12/7/08 at 8:39am
Thread Starter 
Yes, but I can't try all combos in the world, right?
So if someone can prove me that X is better than Y, than I will get X.
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post #10 of 15
12/7/08 at 8:48am
Quote:
Originally Posted by HeadLover View Post
Amm, but you know, I wonder what gives at the end of the line a more bit perfect and more quality for the DAC.
Yeah, but as we say it all depends on the DAC, even if the transport is the same and of great quality. Cause different DAC's have different USB vs. S/PDIF implementation. Some have great USB, but mediocre S/PDIF implementation. While others have the other way around.

So there will be no definitive answer.
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post #11 of 15
12/7/08 at 8:59am
Quote:
Originally Posted by HeadLover View Post
Yes, but I can't try all combos in the world, right?
So if someone can prove me that X is better than Y, than I will get X.
Correct! You probably can't try them all.
But as said numerous times there are too many variables to point out a definitive answer. Like X is "better" than Y in ALL possible combinations...

I put my vote on USB, for the reason posted above. But that don't say I am right.
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post #12 of 15
12/7/08 at 2:47pm
Quote:
Originally Posted by HeadLover View Post
Yes, but I can't try all combos in the world, right?
So if someone can prove me that X is better than Y, than I will get X.
Then the question you are asking is too general!
If you get more specific, like mention 1) your existing setup, 2) what you want to do/change/add and 3) your available budget, we can help much more.
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post #13 of 15
12/7/08 at 3:49pm
Yeah, it would help a lot if you limited the choices. Cause as of now you cover all computers and DAC's (from $5 to $100,000+).
Too wide a choice to be any more specific about what is "best" that what is already said, imo.

Which computer, sound card, DAC, ... do you own or have your eyes on? And how much $$ are you planning to spend?

Example.
I own a MacBook Pro and an RWA Isabellina. The combination allow a direct connection of USB or optical. Based on sound quality only I pick USB for this combination. I just sound move natural and detailed.
Probably because the Isabellina convert directly to I2S to feed the NOS DAC chip. While optical convert to S/PDIF, which add an additional conversion to the process. From what I understand most USB enabled DAC's use an intermediate S/PDIF conversion, and hence don't have the same benefits.
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post #14 of 15
12/7/08 at 3:52pm
Thread Starter 
Amm, I don't know
I am asking it, but not for a specific model
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post #15 of 15
12/13/08 at 10:00pm
I am a bit curious about this as well and have a couple of questions if someone can answer.

1) If I have an X-Fi and a PS Audio DLIII, will there be a difference in quality of signal fed to the DAC if I choose the USB option or the optical option?

2) Would the DLIII process the signal differently depending on whether it comes from the USB or from the optical input?

3) If I plan to spend $1000 on a DAC that will be used exclusively with a PC via my soundcard, would it be better to get one with a good USB implementation or it is just as good to choose one that can only be fed via an optical input? Any DAC recommendations?

4) Given that price range, would you go for a new unconverting DAC or an older (90's) used Esoteric or Wadia?

Thanks so much for any insight into these questions.
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