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Old 16th September 2013, 10:24 PM   #321
ClaveFremen is offline ClaveFremen  Italy
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Originally Posted by SY View Post
That's the beauty of digital. You transmit the bits or you don't.
This is nonsense...There's no such thing as 'pure' digital transmission, every transmission is analog.

To have bit perfect trasmission you need trasmission protocols with error correction, retransmission of data, etc.

Finally for streamed data you don't even need to trasmit and receive all the bits...all you need is to receive the great part of it in a timely manner.

Quote:
Originally Posted by cbdb View Post
Why do you think this is the only way audio is transfered over USB.
There's no a single way to transmit audio via USB.

For instance you can transfer audio as a file but you'll need a buffer to seamlessly play it and it will not be realtime.

BTW Isochronous trasmission can be done both synchronous or asynchronous (the difference is in which clock the trasmission use)
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Old 16th September 2013, 10:28 PM   #322
SY is offline SY  United States
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Quote:
Originally Posted by ClaveFremen View Post
This is nonsense...There's no such thing as 'pure' digital transmission, every transmission is analog.
If a system is digital, the bits are transmitted and received or not. There's no "in between." If the bits aren't transmitted and received, there's dropouts if and when the lack of transmission/reception exceeds data correction. You recite a nice slogan, but that's all it is.
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Old 16th September 2013, 10:38 PM   #323
ClaveFremen is offline ClaveFremen  Italy
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Quote:
Originally Posted by SY View Post
If a system is digital, the bits are transmitted and received or not. There's no "in between."
Sorry, false.

If the analog transmission representing digital data can't be interpreted there's an error.

If the transmission protocol provides a method for retransmisson you can then request again the missing data.

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Originally Posted by SY View Post
If the bits aren't transmitted and received, there's dropouts if and when the lack of transmission/reception exceeds data correction.
You're supposing the protocol provides retrasmission, there are protocols that don't do it.

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You recite a nice slogan, but that's all it is.
Nicer than: That's the beauty of digital. You transmit the bits or you don't. ?

BTW mine is not a slogan but a simple, plain fact that every electronic engineer (should) know.
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Old 16th September 2013, 11:03 PM   #324
SY is offline SY  United States
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Quote:
Originally Posted by ClaveFremen View Post

If the analog transmission representing digital data can't be interpreted there's an error.
Yes, dropouts, if the error is great enough to cause correction to fail. You'd have to really work at it to cause this to happen, though no doubt some high end cable peddler or ignorant diy-er could have managed the feat. A cheap USB cable from any normal retail outfit will work perfectly in this system.
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Old 17th September 2013, 12:38 AM   #325
Greg Erskine is offline Greg Erskine  Australia
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Are we still in context?

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Originally Posted by lowtherdream View Post
Post #1: Context: PC or other digital source connected via USB to an external DAC.
Am I right in assuming there is no error correction at all?

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Old 17th September 2013, 06:35 AM   #326
marce is offline marce  United Kingdom
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This is nonsense...There's no such thing as 'pure' digital transmission, every transmission is analog
This is wrong, I'm sorry but digital transmission is digital transmission.
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Old 17th September 2013, 07:52 AM   #327
ClaveFremen is offline ClaveFremen  Italy
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Originally Posted by marce View Post
This is wrong, I'm sorry but digital transmission is digital transmission.
Hi Marce,

can you elaborate?

While it's obviously true that "digital transmission is digital transmission" (truism), at the physical layer you transmit analog waveforms representing digital data, like pulses, squarewaves or a limited set of continuously varying wave forms (passband trasmission).

So, at the physical layer, digital transmission is still subject to physics and so to errors, which can be handled, if needed, at higher levels by transmission protocols (error checking, error correction, retransmission).

The whole digital domain is actually an abstraction.

Where am I wrong?
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Old 17th September 2013, 08:01 AM   #328
alan1977 is offline alan1977
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yes my understanding of USB audio transmission was slightly wrong
Isynchronous (sp) is waht hte majority of DACs handle from what ive seen, data is streamed in 0s and 1's, the DAC doesn't care if what it receives is what's sent, it just handles the signal and converts it to analog.
Asynchronous (sp) is more like hte method for which you would transfer data which cannot be received incorrectly, the data is checked, and resent if necessary before being processed, there are Asynchronous DACs available after research, which in theory shoudl completely remove the need for an overpriced cable? should it not?

So, to summarize... if you have an isynchronous DAC, the quality of the cable can potentially affect the recieved signal. Can you hear it? that's another matter completely

I hope i have this right please feel free to correct me
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Old 17th September 2013, 08:08 AM   #329
sq225917 is offline sq225917  United Kingdom
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I smell entrenched positions, time for some posters to look at the bigger picture.

2nd order effects exist, fact!
Cables can't filter the data, fact!
Data either passes with a high enough accuracy to completely recovered or it does not, this in independent of resending, fact!

It would be nice if someone who claims 'better' cables can make an audible difference could point to blind listening tests that back up that position. Surely if 2nd order effects were audible there must be some way to 'queer' a test to prove it?

That no manufacturer yet has points to the truth.
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Old 17th September 2013, 08:13 AM   #330
ClaveFremen is offline ClaveFremen  Italy
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Quote:
Originally Posted by sq225917 View Post
Data either passes with a high enough accuracy to completely recovered or it does not, this in independent of resending, fact!.
Sorry, false. See again Isochronous transfer.
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