Passive means a simple step-down transformer is employed so there is no electronics, batteries or phantom power required as is typical with active direct boxes. The DB500 has two 1/4-inch jacks at one end of its enclosure and a single XLR male connector at the other. The two 1/4-inch jacks are paralleled so that the guitar's signal passes thru to your amp while an XLR mic cable routes the instrument's converted signal to the recording or live mixing console.

I received a DB500 for evaluation and it went right to work at my Tones 4 $ Studios for recording guitar. I record guitars direct so I can play them through different guitar amps later. Called reamping, it worked perfectly and sounded true to the guitar due, in part, its high input impedance not loading the guitar's pickup circuitry. I liked its small size, all-metal box, and super rugged construction. It has a ground lift switch that connects (or not) the ground of the instrument (and therefore amp) to the studio's ground via the XLR connector. This is to eliminate a possible ground loop and/or buzz plus possible shock hazard.

I prefer passive direct boxes like the DB500 to active ones for a number of reasons. More expensive active boxes "color" the sound and can become noisy if the battery is weak. They are also subject to interference from nearby radio stations and cell phones. When recording a guitar or a bass with high output active pickups, an active DI box has a little too much "activity"--it applies extra gain that the following mic pre-amplifier may not handle properly. A passive direct box works better and sounds more "present" in these cases.