Mono Active Direct Box. Samson's MDA1 Mono Active Direct Box combines premium sound circuitry with durable, roadworthy construction, providing high-quality signal connection solutions for live sound and recording studio applications. The MDA1 operates on either batteries or phantom power and allows clean, balanced lines to be sent from your guitars and basses. Features include:; All-metal, impact resistant design; 2-position 0dB/-15dB attenuation switch; Ground Lift switch; 1/4"; Input and Thru; Balanced XLR output; 48V Phantom and 9V Battery power options