[LAU] Jack sample-rate

Fons Adriaensen fons at linuxaudio.org
Mon Dec 14 22:13:03 UTC 2015


On Mon, Dec 14, 2015 at 09:09:16AM -0800, Len Ovens wrote:

> The "dedicated ADC" says a lot as the average Audio ADC that runs at
> even 192k or higher still has analog ciruitry BW limited to around
> 20K. I would imagine for this use, 12 bits at 96000hz with analog
> circuitry that is bandwidthed from around 10k to 50k might work
> better than an "Audio card".

Depends on how it works. Just like DA converters can be upsampling,
an AD converter could actually sample at a much higher rate than
the nominal one and then downsample digitally - for the same reason
as the DA: it allows to use a simpler analog antialising filter.

With such an architecture, switching to 96 kHz would provide the 
full, near FS/2, bandwidth even if that isn't very useful for audio.

> I am not sure how much the bit depth
> affects this process but do know that the noise floor of an off air
> signal is not anywhere near 96db below any peak signal.

No, but you can have a very low level signal which you want to
demodulate very near (in frequency) to a high level unwanted
signal. In other words, you need high dynamic range *before*
the demodulator, even if the demodulated signal can have a low
S/N ratio. High linear dynamic range is one of the things you 
pay for with the more expensive receivers.

Ciao,
 
-- 
FA

A world of exhaustive, reliable metadata would be an utopia.
It's also a pipe-dream, founded on self-delusion, nerd hubris
and hysterically inflated market opportunities. (Cory Doctorow)



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