[LAD] A little quiz about audio measurements...

Niels Mayer nielsmayer at gmail.com
Fri May 28 18:27:06 UTC 2010


On Fri, May 28, 2010 at 8:37 AM,  <fons at kokkinizita.net> wrote:
> On Fri, May 28, 2010 at 08:30:54AM -0700, Niels Mayer wrote:
>>[...]
> You're close. See the extra hint in a previous post.

It the "close" has to do with jitter:

* Something on the USB bus is causing a "periodic jitter" with a cycle of 100Hz?
* Something is causing a buffer to become empty every 0.01 seconds and
causing a periodic desync?

If the "close" has to do with induced or actual 50hz hum, perhaps
frequency-doubled via rectification:

* something in the  USB power supply, as well as how that power supply
floats w/r/t ground (ground noise) is the source.

Which would agree with the Wolfson experts from
http://wolfsonmicro.com/uploads/documents/en/Specifying%20Jitter%20Performance.pdf
stating "One of the authors once spent several days trying to track
down a low-frequency jitter problem, only to find that it was in fact
a problem of LF noise on the voltage reference."

Niels
http://nielsmayer.com



More information about the Linux-audio-dev mailing list