Radial StageBug SB-4 DI box

Radial StageBug SB-4 — Piezo-Optimized Active Direct Box

The Radial StageBug SB-4 is a compact active direct box purpose-built for piezo-electric transducers on classical guitar, violin, mandolin, dobro, and upright bass. This DI is the right choice for acoustic players who need a clean, balanced signal at the PA without the harsh peaks and \"quack\" typical of under-saddle pickups. Its 5MΩ input impedance broadens frequency response and tames the resonant spikes that often force sound engineers to pull piezo channels down in the mix.

What makes the SB-4 stand out

Unlike standard DIs that load down a piezo's high-impedance output, this model uses a piezo-optimized active buffer that preserves the natural top end of an acoustic instrument. A high-pass filter and 180° polarity reverse switch give you fast control over stage feedback and resonance.

Signal path tuned for piezo transducers

Engineered for the high-impedance output of bridge-mounted and under-saddle pickups, this unit delivers a smoother top end than a generic DI.

• The audio circuit utilizes a piezo-optimized active buffer to preserve natural acoustic tone.
• Input impedance: 5 MΩ — broadens frequency response and reduces peaks
• Output impedance: 330 Ω — drives long XLR runs without loss
• Frequency response: 20 Hz – 20 kHz — full-range signal to the PA
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Power and connections

Phantom power from the console keeps the unit running with no batteries to forget.

• Power: 48 V phantom, 5 mA — bus-powered from any console
• Input connector: 1/4\" TS — standard instrument input
• Main output: XLR balanced — feeds the PA over long cable runs
• Aux output: 1/4\" buffered — drives a stage amp without loading the input
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Stage-ready controls and construction

Built for daily gigging, this model packs its controls and rugged chassis into a footprint small enough to live inside an instrument case.

• Construction: 16-gauge steel chassis — protects the circuit from stage abuse
• Size: 114 × 47 × 34 mm — slips into a guitar or upright bass case
• Weight: 250 g — light enough to forget it's in the case
• Controls: HPF, 180° polarity reverse, ground lift — fast feedback and hum control
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