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From: Terry G0EZY <GW0EZY@sky.com>
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Date: Fri, 9 Feb 2018 16:35:38 +0000
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Subject: Re: LF: Testing Audioinjector Octo with RPi3
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Hi Paul

I'm following your progress with interest as I have a couple of Octo/RaPi3.

Did you get this request from Amazon:

"As someone who owns Octo 8 channel sound card..., can you help this 
fellow customer?
Piers asked
"Hi there, does the sound card deal with the inputs synchronous? i.e. 
will it load to the pie all 6 input channels synchronously?" "

I think the answer is no?

Terry


On 09/02/2018 11:59, Paul Nicholson wrote:
>
> I'm getting about 2 degrees standard deviation of phase
> measurements of the 19531.25 Hz reference, taking one
> measurement per second.  The 2 degrees equates to about 285
> nS timing jitter.
>
> The PPS intervals have a mean absolute deviation between about
> 190 nS and 300 nS with long term average 256 nS.
>
> So the two measurements are commensurate.
>
> For a sanity check on the reference I set it to 39062.5 and
> allowed the VLF rx to sniff the signal with good S/N and
> measured a standard deviation of phase of about 0.46 degree
> on one second measurements, corresponding to 33 nS jitter.
>
> That really points to the sampling clock of the Octo bouncing
> around.  The sample clock comes from a 49.152 Mhz crystal
> oscillator divided by 512.
>
> By way of confirmation, I replaced the Octo audio interface with
> a stereo Audioinjector (also from Flatmax Studios).  Leaving
> everything else the same.  With this audio interface, the PPS
> is showing between 20nS and 30nS jitter of the pulse centroid.
>
> -- 
> Paul Nicholson
> -- 
>
>