Difference between USB from computer, and coaxial/optical from CD Player

After comparing my connection of USB from HTPC and CD Player digital output, I was surprised to find the difference - CD digital sounds better than the USB from HTPC. In my mind, there shouldn't be.

The following are my connection:

On HTPC, I play iTune on files Apple Lossless, USB out, to USB in on the A/V Receiver H/K 745.

From CD changer, coaxial cable to coaxial input on the A/V Receiver H/K 745.

In my mind at the input level to the Receiver: usb and coaxial are all digital.

Anyone can help decipher this issue? Propose any settings on my HTPC, which uses XP pro.

Quote:

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Originally Posted by chris650

After comparing my connection of USB from HTPC and CD Player digital output, I was surprised to find the difference - CD digital sounds better than the USB from HTPC. In my mind, there shouldn't be.

The following are my connection:

On HTPC, I play iTune on files Apple Lossless, USB out, to USB in on the A/V Receiver H/K 745.

From CD changer, coaxial cable to coaxial input on the A/V Receiver H/K 745.

In my mind at the input level to the Receiver: usb and coaxial are all digital.

Anyone can help decipher this issue? Propose any settings on my HTPC, which uses XP pro.

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First of all, if you're using less than Lossless format, that would explain a lot. :eek:

But assuming the computer source is lossles -- bear in mind that the processing path is different. Unfortunately those more technically inclined than I will have explain why it might sounds different.

I feed iTunes to an external sound card via USB then hence to standalone DAC via coax. I feed the same DAC from my CDP via optical. I notice no decernable difference.



There are a couple of folks here at AR who might know. Otherwise you might pose the same question at of these Audio Asylum where there are some quite knowledgable, (and very opinionated), people ...

• http://www.audioasylum.com/audio/digital/bbs.html
• http://www.audioasylum.com/forums/pcaudio/bbs.html

i said i was using apple lossless.. what do you mean less than lossless????????

Quote:

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Originally Posted by chris650

i said i was using apple lossless.. what do you mean less than lossless????????

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You did, Chris. And I did not misunderstand you.

All I might, (and I said if for benefit of other readers), is that if you had, instead, been using a lossy format, say 128bps, then that would result in noticably inferior sound versus direct CD playback.

iTunes has a built in EQ that can be on or off. If it's on, the USB signal would be processed in a way that the CDP digital would not. This could be a source of difference. Also, using the USB out puts the signal under the control of the computer's system volume so it can be attenuated/processed there also.

You didn't say 'how' it sounded better. It could be as simple as a voltage/volume difference between the two paths, and not necessarily a quality difference.

anyone can provide some sensible comment...?

Quote:

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Originally Posted by chris650

anyone can provide some sensible comment...?

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I for one cannot. I've heard of no simple, blanket reason that can explain why your CDP should sound better than Lossless from your computer via USB.

You got some well-informed USB comments here ...
http://www.audioasylum.com/audio/dig...13/133867.html

You also some comments regarding kmixer vs. ASIO, and the like. I believe my external sound card, the M-Audio Audiophile, use ASIO protocols: assuming that true, maybe that is the reason I don't hear the sort of difference you do. Then again, maybe it doesn't. From what I've read, ASIO is mainly relevant in that it has lower latency than kmixer; on the other hand, I select high latency for my M-Audio to avoid playback dropouts. So who the heck knows?

For some brief ASIO vs. kmixer comments, see here ...
http://en.wikipedia.org/wiki/Audio_stream_input_output

Quote:

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Originally Posted by chris650

anyone can provide some sensible comment...?

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Unless you're capable of describing "HOW" it sounds better or worse, you're not going to get an answer that is more sensible. USB can be voltage/volume attenuated even though its digital. That's the most likely answer. Attenuate the volume and you perceive less dynamics. And, any audiophile knows that volume levels have a huge impact on how the listener perceives the quality of what they listen to.

It ain't rocket science, and digital is digital.

You want to try to describe what you think you hear?