[time-nuts] disciplining sound card

gary lists at lazygranch.com
Fri Jul 6 21:13:22 UTC 2012


With an oversampled ADC (which virtually all soundcards use these days), 
do you really know when a sample was taken?

For the traditional ADC that used a sample and hold followed by 
successive approximation, you knew the moment of sampling. For MASH 
converters, I'm not so sure.

For high accuracy spectral analysis, the 10MHz scheme should be better 
than a stock soundcard.


On 7/6/2012 12:40 PM, Tristan Steele wrote:
> Another option is to do it yourself, it is one of my projects that is currently in progress. I have some early information at:
>
> http://electronics.ozonejunkie.com/category/electronics/time/10mhzaudio/
>
> I am aware that the jitter will not be all that low, but I was more interested in longer term stability.  I have since made a smaller, neater board that just needs to go through some testing.  If there is interest, I can post schematics up in the next few days.
>
> Tristan
>
> On 06/07/2012, at 20:13, lists at lazygranch.com wrote:
>
>> I'd suggest hacking USB type soundcards. It is certainly easier to get at the guts.
>>
>> There is a Chinese card peddled by a few vendors on ebay that comes in a blue metal case. You can slip out the PCB. The card uses CMedia chips.
>>
>> This is the first one I spotted on ebay:
>> http://item.mobileweb.ebay.com/viewitem?itemId=280506784055&cmd=VIDESC&index=19&nav=SEARCH&nid=33879388392
>>
>> I have an older version. These CMedia based cards work well under ALSA.
>>
>>
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