Frekvens - noise even in low volume

Hi everyone,
I recently buy a frekvens ikea speaker, the one with the woofer. Until now everything was fine. I was very happy.

But today, I noticed a noise (like ground noise). It is there even when the volume knob is at the lowest level.
I should also say that I noticed it since I used the speaker connected to my op1. I mean that I do not know if it was already there when I was only used the speaker with Bluetooth. But it it noticeable with wire and Bluetooth.
Is someone has the same parasite sound?
It is really enjoying when using the speaker at low volume.

Yes, mine does the same, I think it’s a ground loop, the wiring must be low quality. There is no such noise when using batteries.