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USB cable really improves?

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    Posted: 08 Jan 2013 at 4:46am
Hello everyoneTongue,
 
I've looked for and tried to learn from the internet thru a lot of forums and I can draw the conclusion that there is quite divisive stands Angry on whether different USB cable connecting the PC and the DAC can really make a difference.  I've seen many people with technical backgrounds think that it is really a joke LOL, while the other side would say that they could actually HEAR it no matter what proves were given! Smile
 
I've just bought a new dac and wondering whether I should buy something like the Furutech Formula2 to partner it, would anyone advice me on this issue? Thanks a lot for your help! Wink
 
Lapkwan.
 
 
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Post Options Post Options   Thanks (0) Thanks(0)   Quote lapkwan Quote  Post ReplyReply Direct Link To This Post Posted: 08 Jan 2013 at 5:05am

To supplement my previous post, I've found that there have been much much less argument on other cables particularly the anologue ones such as the speaker cables, but the debates out there are particularly heated for USB cable, which incorporates something called the FIFO (first in first out) mechanism, and by which those in the knows (not me) claim that would make the cable isolated from anything concerns with sound quality. I must confess I am in a mess!

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Post Options Post Options   Thanks (0) Thanks(0)   Quote GoSUV Quote  Post ReplyReply Direct Link To This Post Posted: 08 Jan 2013 at 7:19am
At first, I was a skeptic like you and did not think USB cables made any difference at all to the sound. After all, digital is digital and 1 is a 1 and 0 is a 0, if my files transfer to the hard disk without a single bit error, why would my audio file not get to the DAC with all the bits intact? Like many of those critics I have a technical background as well. But one day by accident, I swapped the USB cable connected to my DAC, and immediately heard something was wrong. I thought my DAC or amp was bad because it lost all dynamics and was so lifeless, but nothing else was changed. I swapped the original cable back and everything was fine again. By that point I was convinced. Originally I had always just used the USB cable from a portable harddrive, but at that moment, I was using the harddrive so I just took another USB cable from a cheap dollar-store USB hub, and those two cables are obviously built differently. They were similar in length. Finally I bought a proper USB cable from an audio brand and was happy.

Technically, what is the difference between transferring a file from a computer to a portable hard drive, and playing an audio file from the same computer to a DAC? When transferring a file, the computer's OS (operating system) handles all the handshaking, error detection, correction and retransmission with the harddrive. Since the file only has to get there regardless of whether it takes 0.2s or 0.25s -- errors, or jitters (variations in latency) does not matter too much, as long as the error-detection algorithms can catch it, and retransmission protocols can ask for the failed segments until the entire file is transferred without any bit loss. But sending an audio file to a DAC is different. Instead of transferring, it is actually "streaming", meaning that bits which failed to arrive, or arrive in time, are considered lost, to put it in simplified terms. Streaming does not afford much opportunity for error detection and correction, much less retransmission. So that's why, besides the USB cable itself, the music playing software can also affect sound quality when you use the computer as source (CAS). These specialized music software actually does hog the computer's CPU so that some cycles are dedicated to streaming audio files to the DAC to reduce jitter.

If you still don't believe, it is simple to just bring a laptop computer and a pair of headphones with you to a store, and ask for a demo of a USB cable. Bring along a cheap USB cable as a "reference", and you will hear the difference. By all means, if you can't tell, just save your money and consider yourself (or your wallet) blessed.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote morris_minor Quote  Post ReplyReply Direct Link To This Post Posted: 08 Jan 2013 at 8:31am
I've seen "audio" ethernet cables to, which I guess have the same claims made. I would argue that devices using these would usually have data buffers making the precise timing of bits less vital. But I'm open to other views . . .

(Until recently I was an analogue cable sceptic  - but GSPs CuSat and Spatia have definitely shown me I was wrong on this Embarrassed).
Bob

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Accession MC/Enigma, Accession MM, Reflex M, Elevator EXP, Era Gold V
Solo ULDE, Novo, Lautus USB and digital, Libran balanced, CuSat50
2 x Proprius + Spatia/Spatia Links
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Post Options Post Options   Thanks (1) Thanks(1)   Quote Graham Slee Quote  Post ReplyReply Direct Link To This Post Posted: 08 Jan 2013 at 8:34am
In developing the Lautus USB Audio Cable we looked at the FIFO delay and decided it couldn't be used as an against argument, why?

Data still hits the FIFO (first in first out) buffer input in real time, and the USB protocol controller before it.

What the layman doesn't realise is the logical ones and noughts have a fast transition between them, otherwise there would be more than ones and noughts, and that puts a logic gate into a bit of a predicament.

The rise and fall time between 0 and 1 and 1 and 0 obviously needs to be fast - there is no such thing as half! There are however, propagation delays which make the transition slope. Propagation delays are responsible for errors! What is half? The input has to decide if it's a 1 or a 0 and it has no human reasoning, it just does it - right or wrong.

So then the data enters the FIFO, and then the data exits the FIFO. So error data - 1's that have become 0's and 0's that have become 1's are still error data!

That error data is then converted to S/PDIF or analogue and it's still in error.

So what's the cable got to do with it? Here we go again - maybe somebody listens this time?

Cables have capacitance, that capacitance has a "quality" for remembering some part of its charge. Forget resistance, we're talking about CMOS inputs which are very high resistance and you can stick in series resistance and it makes no difference to rise and fall times, so forget all this OFC nonsense!

USB audio data is high speed. Printer data is generally low speed so the cable doesn't matter. Hitch a USB cable from a printer to a PC and see how often it fails to recognise it. Hitch a high speed device like a USB DAC to a PC and see how many times it fails to recognise. Something to do with cable capacitance?

OK, we covered capacitance, but what about other sources of 0/1 corruption? What about RF field strength? Can it be conceived that some radio signal modulation on the data may phase step some data? At an extreme we'd get 0's and 1's inverting, but more than likely we'd get transition edges that are blurred. So how is that blurring going to affect the data?

Better to prevent it? And we can demonstrate that the Lautus does all it promises.

Graham


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Post Options Post Options   Thanks (0) Thanks(0)   Quote Graham Slee Quote  Post ReplyReply Direct Link To This Post Posted: 08 Jan 2013 at 8:47am
To reinforce what GoSUV wrote there is no error checking on USB audio like there is when file sharing.

There is "handshaking" with USB audio devices but only to recognise the device.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Suggs Quote  Post ReplyReply Direct Link To This Post Posted: 08 Jan 2013 at 10:51am
Sounds very convincing to any cable sceptics out there (not me, I'm a convert Thumbs Up)...now all we need to know is when will the Lautus USB cable be available?
Derek
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