The Artec QTB is a discrete clean boost mounted to the back of a potentiometer. This potentiometer has 4 positions - true bypass, 6dB boost, 14dB boost and 20dB boost.
The boost allows you to slam the front end of your amp with exactly the sound that comes directly from your pickups, but with more power. This helps to push your amp naturally into overdrive (no diode clipping from the boost), to allow you to get the tones that you'd typically get by turning your amp volume up a ton at much lower volumes.
The 3 boost positions allows you to quickly switch the gain levels that your amp is subject to - in effect allowing you to use it as a channel switch for your amp. You could set up true bypass as clean, 6dB as breaking up, 14dB as classic rock, 20dB as heavy rock. This would be a great addition with simple single channel amps!
Dimensions:
Length: 25mm
Width (excluding potentiometer shaft): 23mm
Width (including potentiometer shaft): 44mm
Potentiometer shaft diameter: 9mm
Requires 9v battery.
Comes with battery clip.