Why does setting Lo-Band EQ to minimum increase the volume by +3dB on XDJ-AZ?

On May, 21 my new XDJ-AZ arrived at my home. A giant box containing a giant machine. After switching on and getting a firmware update to V1.22, I installed also the driver for Windows. Now it was usable with rekordbox (7.1.3) and I had to do a mix immediately. Works fine, I noticed that my fingers had to adapt from XDJ-RX3 / DDJ-FLX10 for the Play / Cue buttons. While the mix was getting longer, I saw that by reducing Lo-Bad EQ of a playing channel caused a volume increase by +3dB. Not only on channel fader, but also on master volume meter. And, not completely unexpected, this is also visible / audible in the recorded wave file. I did the recording with USB stick plugged into port 1. Same happens if I record it via rekordbox directly in PC. This behavior was new to me, I never saw this before on XDJ-RX3 or DDJ-FLX10.

Can somebody give me an explanation why this happens? I don’t find a reasonable explanation on my own – but it makes EQ mixing difficult for me. And in the forum I found already other entries where the same behavior is described.

The rest is working fine at my place – at least the functions I used so far. One more thing: if I plug the wired headphone (HDJ-X7) I can hear a constant oscillating high frequency signal at very low level. I’m an older guy, but as my ears are still fine, I can hear it. I could narrow it down to the headphone output. This signal is not present in a recording or the normal output. So I think I will live with it – as soon as there is music or any other signal, it’s no longer audible.

Has anybody an idea about the level increase if Lo-Band EQ is set to minimum?

Picture: usually I set the level so 0dB (first yellow LED) is reached. Now, after engaging Lo-Band EQ to minimum, it looks like this:

In the recorded wave it’s also visible.