Topic: Strange ADI-2 Pro jitter issue

So I primarily use my ADI-2 pro as a 'budget analyzer'. Which given the fantastic ADC performance and variable input sensitivity it works extraordinarily well in that application.

However recently my unit has developed a rather unusual issue. Doing a J-test (jitter test) results in a very strange moving/wavy noise pattern. This happens regardless of the DUT and sample rate.

The unit is in 'USB' mode and clock source is internal. No other digital sources are connected.

A video of the issue can be seen here: https://streamable.com/19bu3s

When connecting the DAC I'm testing to a different interface (motu m2) the issue is not there, and as mentioned this shows up regardless of the DAC used.
So it is definitely the ADI-2 and not the source(s).

Does anyone know what might be causing this and how to fix it?
Sometimes changing the sample rate suddenly seems to fix it. But most of the time it just does this.

This didn't happen previously. And when working properly the performance is excellent and i've been able to measure extremely low level jitter products.
https://i.imgur.com/9ugO0wT.pngBut right now the strange/moving noise floor is preventing me from using it.

2

Re: Strange ADI-2 Pro jitter issue

Regrading the video: Does not happen here. I wonder if that is some strange modulation coming from using an unbalanced signal source, depending on the power supply and grounding situation.

Do you see similar stuff with other sources? Can check a balanced source?

Using internal clock the latest firmware update should not change something, but just for the record: you are on 250/102?

Regards
Matthias Carstens
RME