28 May
2010
28 May
'10
6:25 p.m.
On Fri, May 28, 2010 at 05:37:47PM +0200, fons(a)kokkinizita.net wrote:
On Fri, May 28, 2010 at 08:30:54AM -0700, Niels Mayer
wrote:
is that an USB card ?
there is a "small" peak at 1000Hz which looks like a usb power drain at
isochronous packet frequency.
maybe its the packets voltage lifting the local ground a bit.
Audio ADCs and DACs have three important inputs;
the signal input, the voltage reference, and the clock.
Noise and interference on the voltage reference causes
amplitude modulation, and jitter on the clock causes
phase modulation. The resulting modulation products
look very similar in the frequency domain. 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.
You're close. See the extra hint in a previous post.
Ciao,
--
FA
O tu, che porte, correndo si ?
E guerra e morte !
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