Radial SB-4

Active Piezo DI – Compact StageBug

Our price:$149.00 GST
Order Code: SB-4

4 in stock (can be backordered)

Stage Bug SB-4 has the same design and function attitude as the rest of the Radial Stage Bug range – including the essential (non-negotiable) elements for a squeaky clean signal path, and gets it all crammed into a super-compact housing, so there’s no excuse for traveling to a gig without one.

Small enough to stick in a dobro case or cello bag, SB-4 is an active DI (requires 48v phantom), optimised for piezo transducers, to help balance and drive your the instrument output safely to the PA system, without compromising the tone or frequency response.

Input is via a standard 1/4″ input for the instrument pickup. Unlike typical direct boxes that have a 1meg-ohm input impedance, SB-4 features a very high 5meg-ohm impedance that smoothes out troublesome peaks that give piezos a bad name.

…more below…


  • Active DI optimised for piezo transducers
  • Smoothes out peaks, eliminates squawk
  • High pass filter eliminates resonance
  • Ultra compact to fit in your guitar case

Check the entire Radial Stage Bug range here.

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 upwards 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 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 external supply. One simply connects, turns on the phantom power and plays.


Audio circuit type:  Piezo optimized active buffer
Frequency response:  20Hz to 20kHz
Total harmonic distortion:  <0.006%
Dynamic range: 100dB
Input impedance: 5Meg Ohms
Maximum input:  +4dBu
Gain: +2dB
Output impedance: 330R Ohms
Equivalent input noise:  -101dBu
Noise floor: -97dBu
Intermodulation distortion: <0.01%
Phase deviation: 10° @ 50Hz


Switches:  High Pass Filter, Phase, Ground Lift
Low-cut filter:  150 Hz
Filter slope: 6dB/octave
Instrument input: ¼” buffered with piezo optimised load
Auxilary output: ¼” buffered to drive guitar effects, amplifier or tuner
Balanced output: Pin-1 ground, pin-2 (+), pin-3 (-)
Polarity reverse:  180°
Ground lift:  Soft lift with 100 Ohms to ground


Construction:  16 gauge steel chassis & outer shell
Finish: Durable powder coat
Size:  (L x W x D) 114mm x 47mm x 34mm
Weight:  250 grams
Power:  48V phantom power
Conditions: For use in dry locations only between 5°C and 40°C