AD-2, a high-performance preamp for acoustic guitars. - Model Name: AD-2 - Brand Name: BOSS - Function: Acoustic Preamp - Output Type: OUTPUT, LINE OUT - Input Type: INPUT - Number of Knobs: 3 - Power Supply: 9V Dry Cell Battery Type Thank you for viewing. Used indoors only. I was connecting it to an electro-acoustic bass. It works effectively even with a bass.