Barcus Berry 4000 1-Key Grand Piano and Harp Planar Wave System Features include active direct box which includes a 9 volt battery or phantom power, 1/4-Inch monitor output with variable level, balanced, XLR main out with ground lift and output pad switch (0db/-12db). Includes piezo crystal for piano/ harp, 4000 Piezo preamp, adhesive patches, set of 4 rubber feet and instruction guide. Ideal for piano, cimbalom, clavichord, harp, concert harpsichord.