> I'd noticed a problem with running the M-Audio Revolution 7.1 sound
> card at 192KHz as a source in Gnu Radio -- the spectrum was
> all "funny", with the spectrum getting "reflected" about 48KHz,
> almost as if the actual sample rate on the card wasn't correct, and
> perhaps set to 96KHz instead of the expected 192KHz.
>
> To eliminate Gnu Radio as a cause, I used "arecord" with the correct
> parameters to record a 20-second chunk of audio from the card,
> then used Gnu Radio to plot the spectrum. Sure enough, the spectrum
> is still not correct, so I suspect this is a driver issue.
>
> I *know* that I used to be able to use this card at 192KHz several
> years ago, and the card advertises 192KHz sampling as a feature.
>
Yet another follow-up.
It turns out that despite what the hardware reports, the ADC on the
Revolution 7.1 only runs at 96KHz, and the controller apparently does
some kind of half-assed upsampling. Gack!
--
Marcus Leech
Principal Investigator
Shirleys Bay Radio Astronomy Consortium
http://www.sbrac.org
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