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

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To: <fons@...>
Cc: Linux Audio Developers <linux-audio-dev@...>
Date: Friday, May 28, 2010 - 5:40 pm

Dammit, Fons! I'm trying to get some work done today and go
off and nerd snipe me.....

On Fri, 28 May 2010, fons@kokkinizita.net wrote:

>> Noise and interference on the voltage reference causes

OK, here's my guess (standing on the shoulders of guys
like Neil)...

The signal is being amplitude-modulated by a 100 Hz
saw-tooth signal. This signal by itself produces a
tight frequency series in multiples of the fundamental
(i.e. 100, 200, 300, 400 Hz...) and constant
amplitude. When used to modulate the amplitude of the
input signal, it results in a peak at the input
singal's frequency... with symmetric, attenuated peaks
@ 100 Hz spacing (like the ones that you show).

If you change the frequency of the input signal, the
surrounding peaks will move with it to maintain a 100 Hz
spacing.

The 100 Hz (being 2x 50Hz, the power freq. in Italy)
suggests that it is probably related to some manner of
power supply. However, I have no theory why we're
getting 2x 50Hz (and I think I need one :-)).

That the signal is (or is approximately) a sawtooth wave
suggests a capacitor somewhere... either corrupting the
ground signal or creating a ripple in the DC power supply
(rectifier circuit or a broken voltage regulator). I would
probably start by checking the MOBO power supply.

-gabriel

p.s. Nerd Sniping... http://xkcd.com/356/
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Messages in current thread:
Re: [LAD] A little quiz about audio measurements..., Niels Mayer, (Fri May 28, 3:31 pm)
Re: [LAD] A little quiz about audio measurements..., Ralf Mardorf, (Fri May 28, 5:00 pm)
Re: [LAD] A little quiz about audio measurements..., Karsten Wiese, (Sun May 30, 2:06 pm)
Re: [LAD] A little quiz about audio measurements..., Karsten Wiese, (Sun May 30, 4:08 pm)
Re: [LAD] A little quiz about audio measurements..., Niels Mayer, (Fri May 28, 6:27 pm)
Re: [LAD] A little quiz about audio measurements..., Ralf Mardorf, (Fri May 28, 6:39 pm)
Re: [LAD] A little quiz about audio measurements..., Veronica Merryfield, (Fri May 28, 7:14 pm)
Re: [LAD] A little quiz about audio measurements..., Ralf Mardorf, (Fri May 28, 7:17 pm)
Re: [LAD] A little quiz about audio measurements..., Ralf Mardorf, (Fri May 28, 9:24 pm)
Re: [LAD] A little quiz about audio measurements..., Ralf Mardorf, (Fri May 28, 10:33 pm)
Re: [LAD] A little quiz about audio measurements..., Veronica Merryfield, (Sat May 29, 1:59 am)
Re: [LAD] A little quiz about audio measurements..., Gene Heskett, (Fri May 28, 11:56 pm)
Re: [LAD] A little quiz about audio measurements..., Ralf Mardorf, (Sat May 29, 6:30 am)
Re: [LAD] A little quiz about audio measurements..., Veronica Merryfield, (Sat May 29, 6:42 am)
Re: [LAD] A little quiz about audio measurements..., Gene Heskett, (Sat May 29, 3:58 pm)
Re: [LAD] A little quiz about audio measurements..., Ralf Mardorf, (Sat May 29, 7:14 am)
Re: [LAD] A little quiz about audio measurements..., Gene Heskett, (Sat May 29, 4:19 pm)
Re: [LAD] A little quiz about audio measurements..., Jens M Andreasen, (Sun May 30, 5:29 am)
Re: [LAD] A little quiz about audio measurements..., Ralf Mardorf, (Sun May 30, 11:05 am)
Re: [LAD] A little quiz about audio measurements..., Jens M Andreasen, (Sun May 30, 12:29 pm)
Re: [LAD] A little quiz about audio measurements..., Ralf Mardorf, (Sun May 30, 12:35 pm)
Re: [LAD] A little quiz about audio measurements..., Ralf Mardorf, (Fri May 28, 10:42 pm)
Re: [LAD] A little quiz about audio measurements..., Ralf Mardorf, (Fri May 28, 6:30 pm)
Re: [LAD] A little quiz about audio measurements..., Gabriel M. Beddingfield, (Fri May 28, 5:40 pm)
Re: [LAD] A little quiz about audio measurements..., James Morris, (Fri May 28, 6:28 pm)
Re: [LAD] A little quiz about audio measurements..., Veronica Merryfield, (Fri May 28, 6:15 pm)
Re: [LAD] A little quiz about audio measurements..., Gabriel M. Beddingfield, (Fri May 28, 6:23 pm)
Re: [LAD] A little quiz about audio measurements..., Gabriel M. Beddingfield, (Fri May 28, 6:40 pm)
Re: [LAD] A little quiz about audio measurements..., Jens M Andreasen, (Fri May 28, 7:12 pm)
Re: [LAD] A little quiz about audio measurements..., Ralf Mardorf, (Fri May 28, 6:50 pm)
Re: [LAD] A little quiz about audio measurements..., Ralf Mardorf, (Fri May 28, 6:52 pm)
Re: [LAD] A little quiz about audio measurements..., Ralf Mardorf, (Fri May 28, 6:26 pm)
Re: [LAD] A little quiz about audio measurements..., Ralf Mardorf, (Fri May 28, 6:22 pm)
Re: [LAD] A little quiz about audio measurements..., Jens M Andreasen, (Fri May 28, 5:58 pm)
Re: [LAD] A little quiz about audio measurements..., Gabriel Beddingfield, (Fri May 28, 5:50 pm)
Re: [LAD] A little quiz about audio measurements..., Ralf Mardorf, (Fri May 28, 5:57 pm)
Re: [LAD] A little quiz about audio measurements..., Gabriel M. Beddingfield, (Fri May 28, 6:08 pm)
Re: [LAD] A little quiz about audio measurements..., Ralf Mardorf, (Fri May 28, 6:18 pm)
Re: [LAD] A little quiz about audio measurements..., Arnold Krille, (Fri May 28, 5:24 pm)
Re: [LAD] A little quiz about audio measurements..., Ralf Mardorf, (Fri May 28, 4:33 pm)
Re: [LAD] A little quiz about audio measurements..., Ralf Mardorf, (Fri May 28, 4:39 pm)
Re: [LAD] A little quiz about audio measurements..., Ralf Mardorf, (Fri May 28, 3:24 pm)
Re: [LAD] A little quiz about audio measurements..., Robin Gareus, (Fri May 28, 3:05 pm)
Re: [LAD] A little quiz about audio measurements..., Veronica Merryfield, (Fri May 28, 5:00 pm)
Re: [LAD] A little quiz about audio measurements..., Ralf Mardorf, (Fri May 28, 5:21 pm)
Re: [LAD] A little quiz about audio measurements..., Ralf Mardorf, (Fri May 28, 5:37 pm)
Re: [LAD] A little quiz about audio measurements..., Robin Gareus, (Fri May 28, 3:39 pm)
Re: [LAD] A little quiz about audio measurements..., Veronica Merryfield, (Fri May 28, 6:55 pm)
Re: [LAD] A little quiz about audio measurements..., Ricardus Vincente, (Fri May 28, 7:15 pm)
Re: [LAD] A little quiz about audio measurements..., Ralf Mardorf, (Fri May 28, 7:20 pm)
Re: [LAD] A little quiz about audio measurements..., Ralf Mardorf, (Fri May 28, 7:07 pm)
Re: [LAD] A little quiz about audio measurements..., Ralf Mardorf, (Fri May 28, 7:14 pm)
Re: [LAD] A little quiz about audio measurements..., Robin Gareus, (Fri May 28, 5:22 pm)
Re: [LAD] A little quiz about audio measurements..., Jens M Andreasen, (Fri May 28, 8:52 pm)
Re: [LAD] A little quiz about audio measurements..., Jens M Andreasen, (Fri May 28, 9:34 pm)
Re: [LAD] A little quiz about audio measurements..., Jens M Andreasen, (Fri May 28, 10:31 pm)
Re: [LAD] A little quiz about audio measurements..., Florian Faber, (Fri May 28, 4:54 pm)
Re: [LAD] A little quiz about audio measurements..., Ralf Mardorf, (Fri May 28, 5:04 pm)
Re: [LAD] A little quiz about audio measurements..., Chris Cannam, (Fri May 28, 2:53 pm)
Re: [LAD] A little quiz about audio measurements..., Ralf Mardorf, (Fri May 28, 3:05 pm)
Re: [LAD] A little quiz about audio measurements..., Robin Gareus, (Fri May 28, 3:27 pm)
Re: [LAD] A little quiz about audio measurements..., Gene Heskett, (Fri May 28, 2:37 pm)
Re: [LAD] A little quiz about audio measurements..., Florian Faber, (Fri May 28, 1:35 pm)