|
Audio Asylum Thread Printer Get a view of an entire thread on one page |
For Sale Ads |
65.19.76.104
In Reply to: RE: 90ohm impedance posted by Ryelands on July 21, 2015 at 06:58:43
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: 07/21/15Follow Ups:
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
Post a Followup:
FAQ |
Post a Message! |
Forgot Password? |
|
||||||||||||||
|
This post is made possible by the generous support of people like you and our sponsors: