The Radial StageBug SB-2 (part R800 0120 00) is a compact passive direct box built for active basses, keyboards and active acoustic guitars, small enough to live inside an instrument case. A 1/4-inch input and parallel thru jack let the musician feed an on-stage amp or tuner while the DI sends a balanced, mic-level signal over an XLR (wired to the AES standard) to the PA or recording console. Inside is a custom Eclipse ET-DB3 transformer with a 12:1 ratio that handles impedance matching and gives full galvanic isolation, so ground-loop hum and buzz are eliminated; a ground lift switch helps further. A -15 dB pad prevents overload from hot active basses and digital pianos. A stereo-to-mono merge function lets a stereo keyboard or computer be plugged into the input and thru jacks and summed to one PA channel, saving inputs. Radial specifies 20 Hz to 20 kHz (±0.5 dB) response, 115 dB dynamic range and 0.005% THD. It needs no power, is housed in a 14-gauge steel shell measuring 114 x 47 x 34 mm and weighing 250 g, and carries Radial's transferable 3-year warranty.