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In Reply to: RE: Regen Cable posted by ahendler on July 19, 2015 at 07:44:14
speak I guess. Some of the usb cables touted in UK as being A1 are really B10.
Yes, I tried them.
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Nt
Plenty of usb cables claim this.
Indeed, if a cable is sold as a "USB cable" it had better be 90 ohms, otherwise it is defective or fraudulent.
Tony Lauck
"Diversity is the law of nature; no two entities in this universe are uniform." - P.R. Sarkar
Indeed, if a cable is sold as a "USB cable" it had better be 90 ohms, otherwise it is defective or fraudulent.
Meanwhile, back in the real world the spec is, as I recall, 90R +/-15 per cent. USB cables (obviously) vary in how closely they adhere to standards, esp the 90ohm thing, but also very commonly in the gauge of wire used, esp for V+/-. And so on. Many cheap USB cables used to connect, say, external storage are way out of spec but nevertheless work in the sense that they transfer data even if sub-standard engineering ups the number of retransmits and lengthens transmit time. In the scheme of things, that doesn't matter much for casual domestic use esp at the low prices one pays for them. IOW, they are neither defective nor, to use your IMHO unnecessarily melodramatic term, "fraudulent".
Cables for critical real-time signals such as audio are a different matter. It's surely a prime requirement that up-and-after-market cables for applications of this type meet spec as tightly as possible whatever exotico-how's-your-fathers the makers claim to offer. Frustratingly, few makers provide data. I see that Wireworld says that "The Ultraviolet USB exceeds the USB2.0 High Speed specifications". I'm sure it does but it'd be nice to know how and why.
J Swenson is very careful not to say anything that can't be backed by measurements
True but he seems rarely to provide the measurements that back his reports. What he excels at IMHO is observation rather than measurement. I have no issue with that.
The 15% tolerance is part of the standard. This is needed to deal with manufacturing tolerances as well as installation issues. (Bending a cable in a tight radius may create impedance discontinuities.) The tolerance figures into various budgets that ensures that a conforming transmitter connected by a conforming cable to a conforming receiver in a conforming electromagnetic environment will operate correctly.The transmission of audio data over USB is not what I would call critical real time, unlike the situation with SPDIF and AES/EBU. USB is packet based and there is no relationship between the USB bit clock and the sampling rate clock used by the DAC to time conversion to analog.
Tony Lauck
"Diversity is the law of nature; no two entities in this universe are uniform." - P.R. Sarkar
Edits: 07/21/15
It is difficult to see that these internal cables and connectors on MBs adhere to the USB standard. By all accounts, these should be avoided for audio use.
As I have pointed out, the transformation from the A to B connector makes quite a lot of demands on how cables are laid out internally and how these are soldered to the plugs.
A new secure and impedance matched 'standard' for audio is called for.
Note: On my more expensive usb cable (Gemini) and iFi Power combination, the connections are so loose that I have had to crimp the plugs for a more secure mechanical connection. This does not guarantee that internal 'hard' contacts have been made.
[If] internal cables and connectors on MBs adhere to the USB standard.
According to an Intel paper of some years back, they rarely do at least as far as power delivery goes - see link. (The paper predates USB3.) I don't know whether similar points apply to the data lines but I can guess.
A new secure and impedance matched 'standard' for audio is called for.
Agreed though some way of knowing how closely a given product met spec would be a start. Hopefully, those (pricey) PCIe> USB boards sold for audio use do.
D
If a cable doesn't meet that 'standard', whatever that is, it's NOT a 'USB' cable and should not be sold as such even if it to appears to function.
Link below:
If a cable doesn't meet that 'standard', whatever that is, it's NOT a 'USB' cable and should not be sold as such even if it to appears to function.
Thank you. I have copies of nearly all the pertinent paperwork and have even read some of it (that sad) but I'm sure you'll understand that, if the relevant standards boards don't feel the need to police the use of their logos, neither do I. TBH, if a £1.50 USB cable works, I give not a hoot whether or not it's entitled to carry the logo.
It was our rather arcane little niche - USB for high-end audio - I was concerned with. Specs in this sector are a different matter and concern the real world of valid claims and engineering tolerances.
It may be a matter of the 11th commandment.
Tony Lauck
"Diversity is the law of nature; no two entities in this universe are uniform." - P.R. Sarkar
Then it appears you DO agree with Tony after all when he states: "Indeed, if a cable is sold as a "USB cable" it had better be 90 ohms, otherwise it is defective or fraudulent."
Then it appears you DO agree with Tony . . .
As I said above, I have no opinion on the subject. As he is wont to do, Tony seems to be back-tracking from one of his typically OTT pronouncements with a blast of techno-guff. Make of it as you will.
nt
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