Boss AD-2

This is a well made and easy to use pedal, but the FX are so subtle that it is ultimately useless.

I tried using it with a nylon string ukulele and a Cherub external piezo pickup. It does, just barely, round off piezo screech, but adds nowhere near enough gain to properly drive an electric guitar amp.

Other effects: the "Ambience" (reverb) is OK, though noisy, but the "Acoustic Resonance" and the "Notch" filter seem to do bugger all.

So far, I have tried the L.R. Baggs Para Di (feedback hell and too expensive) and L.R. Baggs GigPro (great, but really, really difficult to change the batteries; you have to yank out the whole PCB!)

Conclusion: I've given up piezos, preamps, and all that malarkey, and gone back to using a mic.