@emilernebro
Thank you Emil!
I've looked it up. It's 44 mm. Good to know!
I've started experimenting with an acoustic guitar which has a 42 mm wide nut. It feels too small for my hands but! .... the problem with the unclean muted sound is gone. Apparently i have to try other sizes too untill i have found the right one.
It is a huge relief for me now!
Thanks again!
Best regards,
Kavi