White noise on audio and MIDI, is it normal?

I insert a TR-6S on stereo audio channels into the Digitone. Unfortunately, there is some noticeable white noise in the background (L & R volume of external audio from 70 to 100).
Also, strangely, there is the same white noise with the MIDI tracks when their volume is up… even when no MIDI is entered in the device! Is it normal?

(note that it is of no consequence ultimately, since I dispatch everything independently in the mixer for recording. But still, when I’m working on the composition, it’s more practical to have the drum-box entered into the Digitone).

Also… I LOVE my Digitone :blue_heart: