[time-nuts] Sound cards

[Bruce Griffiths]

Magnus Danielson wrote:
> J.D. Bakker skrev:
>   
>>> Maybe I lost track and missed something, but I don't think I ever saw
>>> more on the subject of specific high-end sound cards that might be
>>> useful for nutty measurements.
>>>       
>>  From an earlier list message:
>>
>>     
>>> [F]or best noise/jitter-performance an external ADC should be used, 
>>> connected through a digital link to a PC sound card. One could do a 
>>> lot worse than the TI PCM4222 eval board 
>>> (http://focus.ti.com/docs/prod/folders/print/pcm4222.html), which 
>>> accepts an external clock if so desired. At $149 (plus a tenner or 
>>> two for the sound card) this will likely be much cheaper than an 
>>> equivalent FireWire-device.
>>>       
>> The digital link in question is S/PDIF; with the current popularity 
>> of Home Theater systems cheap cards with digital I/O have become 
>> quite prevalent. As an added bonus, S/PDIF can be run over both 
>> coaxial and optical media, the latter being attractive in further 
>> isolating PC noise from any measurement setup. And of course, a 
>> manufacturer's evaluation board is much better documented and more 
>> suited to measurement-specific mods than a random sound card.
>>     
>
> The optical link commonly being used for S/P-DIF is TosLink and it seems 
> like it can be the cause of many problems. It seems like some care in 
> doing the optical link setup is needed. I have never digged into why the 
> optical links have that problem. I can only guess, but bad optical 
> coupling seems reasonable. The multimode "fiber" seems to be leaving one 
> or two things to ask for.
>
> Cheers,
> Magnus
>
>   
Hej Magnus

Relatively high jitter being one problem.
Limited sampling rate being another.

If one has a cheap 16 bit sound card what will it do with 24 bit data
from an external ADC?


Bruce