12 str buzz on B strings ?

[Spence]

My 12str is a plug in option type. It's plugged into a 30Amp with the standard and minimal adjustment knobs. I get a buzz on my B's, especially when moving to another chord.

When it's not plugged in it plays fine. Testing action, I plucked horizontally and no problems with no frets and with frets. Same when plucking normally.

Plugged in again lowering treble on the guitar adjustment helps mute the buzz that's all.

Finger placement is OK, since I do fine when not plugged.

I think the guitar is fine.

Any help is appreciated.