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Radial Engineering
StageBug SB-4 Piezo DI

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Item: N13-1967

Availability: Out of stock

StageBug SB-4 Piezo DI
StageBug SB-4 Piezo DI StageBug SB-4 Piezo DI StageBug SB-4 Piezo DI StageBug SB-4 Piezo DI


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 1/4" input for the instrument pickup. Unlike typical direct boxes that have a 1meg-ohm input impedance, the SB-4 features a very high 10meg-ohm 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 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.

These features combined with the compact size make the StageBug SB-4 the perfect companion for orchestral artists, blue grass players and pop string quartets that need to turn it up when in concert.

Using the SB-4 on classical guitar: Connect your piezo pickup directly to the StageBug SB-4 to get the best tone. No preamp is required! Activate the low-pass filter to eliminate resonance and you are set to go. The SB-4 balances the signal for long runs and smoothes out the peaks for a more natural sounding concert guitar!

Using the SB-4 on dobro: Use the SB-4 with a piezo on your resonator guitar to capture the unique sound of the body. Connect the AUX out to a stage amp if you like and then send the signal to the PA. The SB-4 will help eliminate the mid range squawk and frequency peaks that often force the sound engineer to turn you down in the mix.

Using the SB-4 on upright: Traveling with an upright is expensive! So reducing the size of the ancillary equipment is important. The super compact SB-4 connects from the piezo pickup to the PA and you do not need a preamp in between. The SB-4 delivers a deeper bass and more natural top end, greatly improving your tone through the PA.

The StageBug SB-4 is a direct box designed specifically for piezo equipped instruments. These are commonly used on acoustic guitars, upright bass, violin and classical guitar. The intent with the SB-4 is to bypass any electronics (audio buffers) so that the piezo connects directly to the direct box and the signal is sent directly to a PA system via a microphone input channel.

Before making any connections, ensure all audio levels are turned down or equipment is turned off. This will help avoid plug-in transients that could damage more sensitive equipment such as tweeters.

The SB-4 Piezo is equipped with two 1/4" jacks and an XLR. The input jack is used to connect the instrument and the thru-put can be used to feed your on-stage amp or tuner. The XLR is used to connect to the PA system and for powering the SB-4's active circuit. Power comes from the mixer in the form of a 48V DC current known as phantom power. This handy invention enables the audio in the form of alternating current (AC) to be sent to the mixer at the same time as the 48V DC is sent from the mixer to the SB-4 using the same 3 conductor cable.

Once connected, slowly turn the levels up to a comfortable listening level. It is a good idea to test at low volumes as this helps prevent connection pops that can damage components should something not be quite right.

When amplifying an instrument through a PA system, low frequency resonant feedback is often encountered. This is usually due to low frequencies from the PA system that cause the instrument to vibrate. The high pass filter is essentially a bass-cut switch that reduces the low frequency output from the instrument. If you hear low frequency resonance, push it inward to activate. Reducing low frequencies also helps by removing excess mud, making it easier for the instrument to sit in the mix.

Another similar source of feedback is resonance caused by the room acoustics and the PA system interaction. What happens is that certain bass frequencies can align with the echo causing what is known as a room mode. Modes can either amplify each other or cancel each other depending on the phase. By reversing the polarity, you can often eliminate resonant feedback. Simply depress to check for the best results in a given room.

Some artists like to have a stage amp in addition to the PA and monitors. The StageBug SB-4 Piezo is equipped with a thru output that can be used for a stage amp or a tuner. When it is used with a stage amp, you can sometimes encounter hum and buzz caused by a ground loop. Ground loops occur when the audio ground and the electrical ground conflict. A side access ground lift switch will help eliminate the noise. Simply depress when needed.


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


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  • 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:330k 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 optimized 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
  • General   
  • Construction: 16 gauge steel chassis & outer shell
  • Finish:Baked enamel
  • Size:  (L x W x D)4.5" x 1,85" x 1.35" (114mm x 47mm x 34mm)
  • Weight: 0.55 lbs (250 grams)
  • Shipping size: (L x W x D)8.25" x 5" x 1.75" (210mm x 127mm x 44mm)
  • Shipping weight:0.8 lbs (365 grams)
  • Power: 48V phantom power
  • Warranty: Radial 3-year, transferable

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