Yamaha's AG Stomp is an acoustic guitar preamplifier with built-in microphone modeling and digital effects. With Yamaha's proprietary Acoustic Microphone Modeling (AMM) technology, the AG Stomp transforms the output of ordinary piezo and magnetic pickups or even built-in mics into the sound of studio microphones actually miking the instrument. The AG Stomp emulates eight microphone types: including condenser, dynamic and tube with a choice between close or distant proximity.

The unit has a total of 60 sound programs divided into 30 factory presets and 30 user-defined. There is a four-band parametric EQ with 12 dB cut/boost and sweepable treble, midrange, bass and presence frequencies. The Piezo/Mic blend knob mixes the pickup and the simulated microphone sound. AG Stomp adds on-board effects like four-band chorus, delay, limiting and three reverbs.

The AG Stomp also contains an integrated five-band programmable feedback reduction system for eliminating troublesome on-stage feedback. Four built-in footswitches provide easy access to all programs, effects, feedback reduction and on-board chromatic tuner. Other features include: balanced 1/4-in. stereo outputs; headphone output for practice or additional stereo output; and 44.1 kHz output S/PDIF digital output for direct recording to a digital recorder.