The Radial StageBug SB-4 is a compact active direct box that has been optimized for use with piezo transducers. This enables violin, dobro, mandolin, cello, upright bass, and other instruments that are best amplified using a piezo to be connected without compromising the tone or frequency response.

The design begins with a ¼" input for the instrument pickup. Unlike typical direct boxes that have a 1 megohm input impedance, the SB-4 features a very high 5 megohm impedance that smoothes out troublesome peaks that give piezos a bad name. The higher impedance also broadens the frequency response for a more natural and pleasing sound. The active circuit performs the high-to-low impedance conversion and balances the signal to enable long runs up to 100 meters without loss, delivering spectacular linearity and low distortion throughout the audio range.

To help eliminate feedback on stage, the SB-4 is equipped with a high-pass filter and a 180° polarity reverse switch. The high-pass filter eliminates excessive bottom end, which in turn reduces resonance that can cause the top of the instrument to vibrate. The 180° polarity reverse helps reduce acoustic hot spots on stage by changing the phase relationship between the PA system and room acoustics, which can combine at certain frequencies to create peaks. Reversing the polarity eliminates the acoustic peak without resorting to severe equalization, which only serves to compromise the natural tone of the instrument. Connections include an AUX out for a stage amplifier plus a standard XLR output to feed the PA. Power is derived from the console's 48V phantom, thus eliminating the need for batteries or an external supply. One simply connects, turns on the phantom power, and plays!