linuxaudio.org

On Wed, January 23, 2013 8:17 am, Fons Adriaensen wrote:

quoted text
> On Wed, Jan 23, 2013 at 06:52:12AM -0800, Len Ovens wrote:

>

>> Just looking through TI's ADCs 96k and up. Any on chip audio circuitry

>> (level controls etc.) seems to lower SNR (101 db typ.) which is no

>> surprise. But what I did find interesting is that even 96k and 192k

>> devices seem to optimized for 48k. So the spec of 112db SNR would be

>> true

>> for 48k, but by the time it gets to 96k that is down 3db (noise floor up

>> 3db) and at 192k... not even listed.

>>

>> So 192k is snake oil anyway, I'm not concerned, though I will say the

>> 192k

>> device has better performance at 48K, much smoother frequency response.

>

> Noise in 24-bit ADC is all thermal noise in the analog parts,

> not quantisation noise. If it is measured unweighted it increases

> by 3 dB if the bandwidth is doubled. But for 96 kHz, half of it

> is above 24 kHz, so the noise within the audio bandwidth remains

> just the same. There is no degradation.

>

> The specs should tell you how exactly the SNR is measured. If the

> A-weighted or 20 kHz BW noise increase at 96 at 192 kHz there is

> something fishy.

Unweighted in the specs. Thank you for pointing that out.
--

Len Ovens

www.OvenWerks.net
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