Notch filter, you only need it if you have feedback problems. Easiest way to dial it in is to increase the volume until you get a steady drone and turn the knob until you hear the drone decrease. After that set the volume back to the playing level. It's not always effective and you may have to experiment with amp and guitar positioning. If you're using a preamp with a Phase Inverter switch, pressing it will sometimes help too. When all else fails, turn it down.
The shape switch applies a Mid-range cut. It doesn't "boost" the high and Lows. It's a purely subjecttive tonal choice. The amp doesn't have a MID EQ knob, but you can use the SHAPE and the TREBLE/BASS knobs to tailor the tone to your taste. Experiment until you find what you like.


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