Dear Andy, LF Group,
At 09:59 19/03/2002 +0000, you wrote:
Has anyone tried changing the clock source on a Soundcard for a different
frequency ? For a job here at work we need to sample more accurately than
the usual crystal oscillator (does this sound familiar ?) and at different
sampling rates. It would be ideal if we could push it to 50kHz...
I remember looking at sound card specifications a year or so ago, and
finding that current sound card audio codecs mostly adhere to the Intel AC
97 specification (there are a number of different versions of this
"standard" of course...), which includes a 48kHz sample rate, so 50kHz
should not be pushing it much. You can download it from
http://developer.intel.com/ial/scalableplatforms/audio/ - it contains a
load of info about pin functions etc.
I skimmed through the data sheets for a few compliant devices - although
they offered the same basic sample rates, the way different rates were
implemented was different in every case - some actually had synthesised
clocks that could be tuned in small increments, others ran at a steady
48kHz, and messed around with the data in the digital domain - the upshot
of this was that the ratios between sample rates were not necessarily exact
- so you might end up needing a different clock frequency for each sample
rate you planned to use.
Cheers, Jim Moritz
73 de M0BMU
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