When I searched online for āBlofeld noisy USBā it was striking how many had gotten the advice to look at their USB cables and perhaps ground them. Even from Waldorf.
The only solid advice Iāve read so far, is get rid of the USB cable and use Midi cables. That solved it for me. Iāve had a few synthesizers and peripherals with USB connections, and the Blofeld is the only one that had this problem, so the mystery of the noisy USB connection is likely just a poor USB integration in the Blofeld.
Still love the synth and Iām happy that the problem is now gone.