A tube amp’s ability to soft-clip and compress the pickup signal is the very essence of a good clean guitar sound with long sustain and controlled pick attack. When the input signal to a tube reaches the point of overdrive, the grid of the tube starts to draw current, which soft-clips the pick attack and loads up the coupling capacitor to the previous stage. This phenomenon is called DC-shift, which will push the working point of the tube towards less gain (compression). As the note fades out, the DC-shift fades out as well, which will pull the tube back towards its initial working point while increasing the gain. By designing the tube circuits carefully to ensure smooth DC-shifting through the stages, natural compression can be obtained for clean sounds along with creamy overdrive when the gain knob is turned up.