hello, I think it's a combination of things, the speaker in amp, the eq settings on the amp, the pickups, the guitar, the leads, the acoustics ect. The only thing I recommend is turning the amps treble down and moving much further away from the amp speaker. Also turn the level of the SD1 down to compensate. The relationship between you and the amp position is crucial in eliminating feedback, and if you're really good you can even controll the feedback pitch, aka Joe Satriani's 'Flying in a Blue Dream'