The Barcus Berry 4000-BRB Planar Wave Piano (or 4000 System) is a piezo crystal sensor and preamplifier system designed to amplify acoustic instruments, specifically pianos and harps. The pickup technology captures the sound from the instrument's soundboard, isolating it from ambient room noise and potential feedback. This allows for a clean, full-spectrum pickup of the instrument's natural tone for live performance or studio recording without requiring multiple microphones. The system is designed for quick and easy installation without modifying the instrument. 

The Barcus Berry 4000-BRB system includes a Planar Wave sensor and a 4000XL piezo preamplifier. The sensor is designed to pick up natural energy waves from the soundboard while reducing feedback. The system provides a balanced, full-frequency sound and the active direct box can use either a 9-volt battery or phantom power. It offers both a 1/4-inch monitor output and a balanced XLR main output with ground lift and 12dB pad switch. The sensor attaches to the soundboard with adhesive, requiring no tools or modifications to the instrument.