Measure MOTU M2/4 ADC distortion while using its headphone amp

[Multicore]

It's been reported that the MOTU M2 distorts the input signals when its headphone amp is turned up. I tried to verify this on my M4 and could see the effect.

I used my DAW (Reaper) to generate a 1kHz test tone on output 3, TRS cable from there to input 1, music output to the phones, adjusted phones knob to min, mid and max, and the spectrum analyzer on the recorded signal shows a dancing skirt around the test tone that's bigger with more headphone drive.

That's an observation, not a measurement.

Can you suggest how to quantify the effect? What software can I use (cheap or free)?

 

[Sokel]

It's been reported that the MOTU M2 distorts the input signals when its headphone amp is turned up. I tried to verify this on my M4 and could see the effect.

I used my DAW (Reaper) to generate a 1kHz test tone on output 3, TRS cable from there to input 1, music output to the phones, adjusted phones knob to min, mid and max, and the spectrum analyzer on the recorded signal shows a dancing skirt around the test tone that's bigger with more headphone drive.

That's an observation, not a measurement.

Can you suggest how to quantify the effect? What software can I use (cheap or free)?

A loopback with REW or Multitone Analyzer (both free)

This is a quick and rough guide,read down the next couple of pages for more:

Horrible Crackling from Topping E1x2

Hi! I lurked on this forum a lot when deciding on which interface to buy, and I ended up deciding on "upgrading" from my rudimentary Behringer UM-2 to a Topping E1x2. The first day, it worked great! The next day however, I noticed a horrible crackling noise when I was playing a game and...

www.audiosciencereview.com

 

[Evgenioni]

It seems that this is about this video

The guy in the video says that he watches this effect on different audiointerfaces, but on Motu it is much stronger. Most likely this is the problem of USB power supply.
I could not repeat this effect.