I have said before in answer to this very question if you are using a piezo pick up you have to use a pre amp or they will quack and sound awful. I use a L R Baggs para acoustic pre amp, The Chocolate Brick on my banjo with a Pick Up The World. It is the most banjo sounding pick up I have heard.

I have a twenty year old Fishman under the saddle pick up which I use a Barcus Berry basic pre amp and get very good sound from my old guild. It isn't a perfect acoustic sound but it is good and no feed back. I use an out board shure 57 to give it an acoustic boost and I am happy with that.

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