Mono Passive Direct Box. Samson's MD1 Pro Mono Passive Direct Box combines premium sound circuitry with durable, roadworthy construction, providing high-quality solutions for line, instrument and speaker level signals. The MD1 Pro allows balanced lines to be sent from your instrument long distances without inducing noise. Features include:; All-metal, impact resistant design; Samson STLX Mu-Metal shielded transformer; 3-position0dB/-15dB/-30dB attenuation switch; Ground Lift switch; 1/4"; Input and Thru; Balanced XLR output; No Phantom or Battery power required