UpTone Audio EtherREGEN (Objective Discussion Only)

[vortecjr]

5 hours ago, cat6man said:

and to follow up on superdad's comment above, does the ASR's a/d converter really have a 600ns jitter spec and, if so, does that invalidate the ASR measurements of jitter? 

 

If you want to learn more have a look at this short informative video.

 

 

 

[vortecjr]

15 hours ago, plissken said:

https://www.ap.com/analyzers-accessories/apx-overview/jitter/

If you want to learn more have a look at this short informative video on this subject.

 

 

[vortecjr]

9 hours ago, jabbr said:

@JohnSwenson: I read your white paper.
 

You have identified the well known nonlinearity as described by Rubiola whereby power supply noise at eg 10Hz causes a frequency offset error in a crystal at f +|- 10Hz. 

 

Ok that’s all correct, however:

 

There is not a well identified inverse nonlinearity whereby phase error an an input f +|- 10 Hz is downconverted to ground plane noise at 10Hz. 
 

If there is switching noise from a gigahertz input Ethernet signal, it will cluster at a gigahertz. 
 

On the other hand common mode noise transmission down a cable could cause 10Hz (or 60Hz) noise in a receiver. 
 

There is no known mechanism to say that 10Hz noise transmission by a gigahertz Ethernet cable has anything to do with Ethernet clock jitter as opposed to common mode noise..

I spoke to John a while back and he mentioned someone had done some research into all this. Not sure if it was Rubiola or not.  

[vortecjr]

3 hours ago, firedog said:

 

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

..

 

And he is correct on this.

[vortecjr]

2 hours ago, kennyb123 said:

I was looking forward to this thread as I was interested in a objective take on this product.  Not surprisingly the negative remarks outweigh the substantive objective commentary.  If there more valuable objective assessments were shared here I might agree that it was wrong for Chris to split this off.  
 

Getting to that myself..
 

A comment was made about Amir’s test equipment being able to properly capture jitter. Is that the case or not?  I realize that a video was shared but why not refute what @Superdad wrote directly?  I would find that to be an interesting discussion.  
 

I also wonder about the appropriate way to test the ER’s benefits at the output of a DAC.  What I’m not seeing is as a testable hypotheses put forth on how this would show up at the output. This would have to be tested in a way that can detect the impact of jitter being reduced.  First introduce a known amount of jitter - take a measurement at the output of the DAC - then remove it - take another measurement.  If no difference shows up then adjust the test methodology until it does - then you are ready to test the ER.  Having said all that, this is exactly the kind of discussion I’d expect to see in an objective thread.  In other words, a discussion about devising the correct testing protocol to evaluate the claims made in John’s white paper.  

I posted the video because I thought it would be interesting and provided a different view point. I think Alex was just trying to say that the AP was not useful for the measurements he was interested in which I do not object to.

 

In regards to your proposed test protocol I think (I'm not directly involved in it) that is pretty much what John is trying to do. 

[vortecjr]

1 hour ago, jabbr said:

 

We mixing up what is being tested: there is no one type of jitter and no single way of testing it. The above discussion regards jitter on an SPDIF interface and no question that topic is of interest to DACs.

 

Regarding the EtherREGEN, the jitter being discussed, and which @JohnSwenson discusses in the whitepaper, is jitter on the Ethernet interface: These are drastically different things!

 

Let's start with a few questions:

1) Does common mode or differential mode noise  on an Ethernet interface affect the downstream DAC, i.e. does it pass through one of the Rendu devices? 

2) Does jitter/phase noise in the Ethernet clock itself affect the DAC?

 

1) There is a clearcut electrical mechanism whereby common mode noise causes ground plane noise (e.g. leakage currents) and this affects audio circuits -- eg ground loops. I will buy a measurement of reduced ground plane noise with the EtherREGEN compared to xxx switch as indeed reduction in common mode noise.

2) There is not a clearcut mechanism whereby Ethernet clock jitter causes significant ground plane noise in the audio spectrum. I don't buy, without substantial additional testing, that a reduction in ground plane noise in a DAC results solely from reduction in Ethernet clock jitter.

 

The AP device is not, to my knowledge, capable of measuring Ethernet clock jitter -- can it create a 1 Gbe eye pattern?

 

Have you measured the jitter/eye pattern on the opticalModule? (obviously this will block common mode noise  ) I'm going to assume the AP is not capable of measuring this.

 

 

Come on...you know the answers to these questions. In regards to the Rendu John advised me that he would use one in the measurement because of it's design. I'll ask John to explain why he is using a Rendu so you guys know his reasoning. My AP does not measure eye patterns. AP don't seem all that interested in USB and Ethernet.