Aha! I found the cause:
It is the display that is cousing this noise. When I put my finger (or any other human skin) close to or onto the display, the noise is there.
So the only solution I see is taking care you are not close to the display with your skin.. I have now set the display timer to two seconds, but unfortunately the display does not go off, it only dims (thereby only dimming the noise if it's there). Time for an extra custom function
I also know now why the other microphone, AT822, does not have this problem: I feeds itselsfwith an internal battery, while the SP-TFB-2 needs power from the r-09. So the r-09 only sends out this noise when using mics with plugin power..
off-topinc: I was speaking of a fuzz, but just found out that fuzz does not mean someting like buzz (English is not my native language)...