[time-nuts] Using cheap sound cards for measurements

[Don Latham]

On this track, what's the group opinion as to the best USB sound "card"?
I'm looking for one for time as well as sd radio use. Should have the best
separation, best s/n, highest digitization rate, 24 bit, etc. Any
recommendations?
Thanks
Don

Bruce Griffiths
> Tom Van Baak wrote:
>> Could you sync the sounds cards in software?
>>
>> If you feed an external 1 PPS into the unused stereo channel of
>> each sound card, then you can solve both card-to-card phase
>> differences as well as card-to-card frequency differences with
>> simple software fitting after, or even while, samples are being
>> collected.
>>
>> I use the R-channel for my 1PPS timing, leaving the L-channel
>> for analog input. A time-synced PC can resolve the seconds
>> time-of-day ambiguity.
>>
>> Note that a sharp 1pps will give you 22 us (1/44100) precision.
>> If you used a slower ramp'ed 1pps then software interpolation
>> should give you sub-microsecond precision.
>>
>> If you want to measure the stability of your sound card, see:
>> http://www.leapsecond.com/pages/sound-1pps/
>>
>> Win32 source code to the tool is very simple; see:
>> http://www.leapsecond.com/tools/1hz.c
>>
>> /tvb
>>
> A higher sync frequency than 1Hz, say around 100Hz or so is probably
> desirable for better cancellation of sampling clock phase noise.
>
> Bruce
>
>
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-- 
Dr. Don Latham AJ7LL
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