Originally Posted by: DavesGuitarJourney

I don't think it is a grounding issue. If you look for it there are quite a few posts about this "feature" of the Katana. I knew of the issue and the solution before I bought mine, and was prepared to send it back if the NS didn't completely eliminate the noise. I don't know if this noise is there for every unit or if it is better or worse with different guitars and cables, but it is apparently a fairly common little annoyance. In my experience it was very easy to correct with Tone Studio.

I believe that some of the Boss Katana's have compressors built in.

Compressors limit dynamic range (make the overall sound more conistent in volume, by making the loud sounds quieter and the quiet sounds louder).

When used, the compressor will raise the noise floor, the noise floor is the low level noise you get from the electronics (or even emulated electronics).

If the noise is unbareable, you can always get yourself a noise gate pedal, which will

shut off the singal when below a certain amplitude level.

can be used subtly too.