Topic: Analog input level meter band limit on ADI-2 Pro FS R

Hi, I'd like to clarify which band limit is used for analog input level meter in my new ADI-2 Pro FS R with latest firmware. It should be 40kHz according to docs, but looks like it is a lot higher, which can be confusing. I just noticed that switching to highest sampling rate (768k) in USB mode raises analog input level bars to -45db without input signal. Checking spectrum with Digicheck NG shows that 40kHz noise is -67db and 81kHz noise is -52db. And everything below 40kHz is lower than -70db limit for spectrum analyzer.  So level meter definitely goes to 81kHz and higher. For 192k sampling rate input level meter shows -79db which is less confusing but still high for 40kHz limit.

Is this correct behavior or I miss something?

2

Re: Analog input level meter band limit on ADI-2 Pro FS R

You missed that all the higher frequencies add up. Plus with excessive signals over 40 kHz there is some aliasing. Just patch an analog loopback and use a software sine generator to check it.

Regards
Matthias Carstens
RME

Re: Analog input level meter band limit on ADI-2 Pro FS R

Matthias, thank you very much for reply! As you suggested I used loopback and 81kHz sine wave in 192k sampling rate at -20db and checked input level meter. It showed exactly -20db. Is this correct for 40kHz limit even with adding up and aliasing?
I'm fine with covering whole range for input level meter, just want to confirm that everything is correct including docs. I've posted pictures from Digicheck NG:

https://i.ibb.co/WVsSysB/Digicheck.png

4

Re: Analog input level meter band limit on ADI-2 Pro FS R

Ok, let's detangle this. The manual is not 100% correct. In the chapter Global Level Meter it states:

All level meters (vertical and horizontal) of the ADI-2 Pro are peak level meters with peak hold function, band limited to 40 kHz even at higher sample rates.

In fact there is a difference between pre and post meters. Pre are not limited in FR, Post are. The Global Level Meter screen must show the pre signal for the inputs and the post signal for the outputs as that makes most sense.

If you check the Analyser screen of the Input display and set the Level Meter to Dual (in SETUP) you can see the difference in pre and post display (even with all FX turned off) directly. Even with the self noise, which then shows -98 dBFS, but a small bar up to -45 dBFS @ 768 kHz.

I will change the wording in the manual to make this more clear.

Regards
Matthias Carstens
RME

Re: Analog input level meter band limit on ADI-2 Pro FS R

Thank you very much!