UpTone Audio EtherREGEN (Objective Discussion Only)

[firedog]

On 3/12/2020 at 7:36 AM, Superdad said:

 

Except that the funny thing is, while the Audio Precision Amir worships at is a very nice general purpose unit, it is not that well suited to measuring jitter in DACs. What’s that? Heresy!  Yet if you look at the specifications for the ADC in the top-of-the-line APx555, you will see that its own jitter is 600 picoseconds!  So that will swamp the jitter details of a device under test—which might be in the range of 10s of picoseconds--or ideally less.

 

As I've said elsewhere, John has already measured these effects--with a Wavecrest system better suited to this--at the clock pin of DACs. 6dB improvement at 10Hz offset is what he has seen so far with EtherREGEN. Our tests using a custom 32 bit high-speed SAR ADC and analysis s/w--to show things after the DAC will come later. 

 

 Acc'd to Amir (in quotes), you are incorrectly reading the specs, and don't understand his measurements:

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."that is a spec for the digital input and output in the analyzer, not "ADC:"

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There are three types of digital I/O on APx555: Unbalanced (S/PDIF), Balanced (AES/EBU) and Optical (Toslink). Above is giving the jitter specs for those.

I don't use any of the digital interfaces to measuring jitter. I use the analog output of the DAC which by definition goes into the ADC on the APx555. A spectrum analysis there will then show all jitter sources including the analyzer itself.