Radial Stagebug User Guide
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Using The StageBug SB-4™

The Radial StageBug SB-4 has been designed to be plug & play easy to use. The following describes how to use the SB-4 Piezo with a standard PA and recording systems. For more details, feel free to consult the full manual by clicking on the icon at left.


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.

Making connections


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 ¼" jacks and an XLR. The ¼" input jack is used to connect the instrument and the ¼" aux jack can feed your on-stage amp or electronic tuner. The balanced XLR output is used to connect to the PA system or recording system.

The SB-1 is powered by +48V phantom generated by your mixing console. A red LED located next to the XLR jack indicates when the SB-1 is receiving power. After connecting the SB-1 check the phantom LED. If it is illuminated you are ready to go. If the red LED is not illuminated switch on the phantom power at the mixing console.

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.

Using the high-pass filter

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.


Using the 180° polarity reverse

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.


Reducing ground-loop noise

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. If you hear hum or buzz, simply depress the ground lift switch.