[time-nuts] wtd: WWVB info

[Charles Steinmetz]

Bob wrote:

>Well, at least *some* of the chips out there do 
>not make it to 96 KHz when sampling at 192 KHz. It’s
>been a few years since I dug into them. Back 
>then a chip that had an internal filter that went to 96K
>was very much the exception rather than the 
>rule. If the only point of 192K is getting to a 96K bandwidth,
>a lot of the chip guys missed out on it 
.

192k *audio* ADCs often have input anti-aliasing 
filters that are only 20-50kHz wide.  In that 
case, the point of sampling at 192ks/S is so the 
anti-aliasing filter does not need to have a 
brick wall response (as it would need to have if 
you sampled at 48 or even 96ks/S), so it can have 
a flatter group delay over the range of human hearing.

For this and a number of other good reasons 
(large variations in gain, large DC errors, and 
idle tones, to name just three), one does not 
generally want to use audio ADCs (or DACs) for 
non-audio applications even if there is not an 
internal input filter -- tempting as it may seem 
because they make bazillions of the audio parts 
and they are cheap.  That's what they make "industrial" ADCs and DACs for.

Best regards,

Charles