Acoustic Preamp for piezo film pickups. The EMG-APA-2 Acoustic Preamp has been designed with the needs of acoustic players in mind and is the perfect complement the AT93 and AT125 pickups. It combines a miniature, low-current draw preamp and a 9 volt battery holder in a single package that attaches to your guitar's front block (at the internal joint between body and neck) with two screws.