The Voltage Unit Meter Pedal (“VUMP”) is a guitar pedal-style level indication meter. This unit reads out signal level in the
traditional “Voltage Unit” (VU) scale, which is similar to a decibel (dB) scale, but pegged to a reference value of 0
VU=1.23VRMS. Since sound levels span many decades of pressure intensity, it is convenient to express the level in the
logarithmic dB scale. An increase of 6 dB sounds about twice as loud as the reference sound level.
The intended use for this device is to be the last “pedal” in a chain of pedals connected to an electronic instrument such
as an electric guitar or bass guitar, or microphone. It provides a convenient, local measure of your signal level just before
going to the amp or a sound board. You can also precisely equalize the volume settings of your pedals using this device. 

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Review by Talk Bass.com

Manual

Analog-VUMP

You’re on stage in between songs. You just changed your pedal settings and the next song is about to start. How are your levels? Too high? Too low? Maybe you’re not sure until the song starts and you hear yourself. Well, if you just had the Mini-VUMP (Voltage-Unit Meter Pedal), you could hit the Mute switch, strum your guitar, check your levels, and discover you left the Boost pedal on before you embarrass yourself on the next song!

You can also use this device to equalize the loudness of your pedals on your pedalboard! Just turn one pedal on and off and change your gain settings one pedal at a time.