USB Dacs - what for?
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Don Quichotte

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Sorry if this question has been adressed before. What is the advantage (if there is any) of an USB connection between a computer and an external Dac compared to using a (coaxial or optical) soundcard output with the same Dac? I am talking about sonic advantages - maybe something related to jitter?!?
 
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tschanrm

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While I don't know all the technical merits, I know that the USB DACs will exhibit similar jitter problems. This is because USB audio is still streamed over, it is not the same type of transfer as say a USB hard drive has. There's more than one thread relating to this, and I've read an article about the issues with USB audio. I'll see if I can't find that USB article for you, its an intersting read. : )

And the advantage I guess is there is one less piece of equipment in the signal path. Instead of going from S/PDIF from Sound Card---->DAC----->Stereo, your just go Sound Card(or USB DAC)----->Stereo. Although, of course, this does not guarantee that the latter combo will produce better sound.
 
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clarke68

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If there are specific sonic advantages to an outboard usb dac, it has to do with the commonly held belief that PCs produce large amounts of EMI (or RFI? Or both?) and you should move your D/A conversion as far away as possible.

More practically speaking (for me): I do a lot of listening at work, where I'm not allowed to add PCI soundcards at will. Also, it allows me the additional flexibility of using any outboard DAC I want, rather than what's on the (comparatively) few audiophile grade soundcards available.
 
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ToddW

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not to change topic or anything, but i have an imac G5 with optical out and would like someway to convert it to some type of preamp linout. anyone got any ideas.
 
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clarke68

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Quote:

Originally Posted by ToddW
i have an imac G5 with optical out and would like someway to convert it to some type of preamp linout.


Use a digital/analog converter, or DAC. Many are available, from quite cheap to very expensive.
 
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sygyzy

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I think the argument for USB DAC over PC Soundcard digital out to DAC is because some systems simply don't have a high-end enough sound card with SPDIF out. But every system has USB.
 
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The issue of jitter will depend on where transfers are done isochonously or asynchronously. Asynchronous transfers would eliminate the jitter introduced by S/PDIF transmission.
 
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Don Quichotte

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Quote:

The issue of jitter will depend on where transfers are done isochonously or asynchronously. Asynchronous transfers would eliminate the jitter introduced by S/PDIF transmission


Isn't asynchronous transfer more or less the same thing (or at least has the same effects) as the reclocking done by some stand-alone Dacs? Let's take the Apogee Mini-Dac for example: it does reclock the data received via S/PDIF and can be connected via USB to a computer. Any reason for the USB connection method to sound better than S/PDIF? (let's assume the S/PDIF out of the soundcard is bit-perfect)
 
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robzy

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Another reason is that a lot of sound cards resample the audio before it even for digital out.

Rob.
 
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Oliver :)

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Quote:

Originally Posted by ToddW
not to change topic or anything, but i have an imac G5 with optical out and would like someway to convert it to some type of preamp linout. anyone got any ideas.


Bear in mind that the iMac will not allow adjusting the volume once you use the optical out. You are left with on/off. The levelmeter in iTunes / Quicktime still work though, therefore you can gain your volume control back (at least for iTunes) with the highly recommended SizzlingKeys http://www.yellowmug.com/sk4it/
 
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