Simple (I hope) cable question

[JohnSwenson]

On 9/25/2017 at 2:20 PM, gmgraves said:

 

Yes, a 20 ft USB cable is non-trivial. Suspect that it would work reliably, but I hesitate to say that there is no degradation of the music signal. I suspect that the error rate would go through the roof, and error correction would be working overtime. And if the errors force the DAC into interpolation, one can certainly hear it! 

There is no error correction in isochronous mode which is what USB audio uses. There is a CRC that can be checked at the receiver, but no way to correct or resend.

 

About a year ago I did a whole bunch of tests on actual error rates of different USB cables for USB audio.

 

Real cheap basic cables: errors started showing up after about 5 feet, so 3 ft cables do well but 6ft and longer can cause problems.

 

Good quality but still inexpensive cables do better, they can be good up to about 10 ft.

 

The Supra cable was the only one I had that had no errors over 10ft.

 

I did not try any of the really expensive "audiophile" cables. My guess is they would be worse than the Supra.

 

I have tried the Corning and for me in my system it worked very well. Others have not had this experience

 

John S.

[JohnSwenson]

14 hours ago, Em2016 said:

 

Hey John, did these cheap basic cables that had errors showing up, even include High Speed Certified USB cables?

 

All these tests were high speed going from a computer into a high speed DAC (actually several DACs) using a protocol analyzer to measure errors at the DAC end.

 

I didn't go out and buy any cables for this test, just using the ones I had in my USB cable drawer (about 50 cables). None of these cables actually have the high speed mark molded into the cable, so I don't know which ones were officially certified as high speed.

 

Results did vary from cable to cable, I did not mean that ALL cables showed errors at exactly 5 feet, but that one cable had a few errors at 5 feet. At 6 feet a few cables had a few few errors. At 10 feet a fair number had a few errors a one or two had a lot of errors. etc.

 

I was not trying to be the cable police so I did not try and figure out what companies these were. In a lot of cases there was no identification mark on the cable, making it impossible to tell where it came from.

 

The reason I brought this up is to let people know that errors DO occur on USB cables, and the longer the cable the more likely this is to happen. This IS important for audio since there is no error correction for audio data.

 

John S.