The FET Driver captures the rich, creamy sound of an overdriven tube amplifier with Hi and Lo boost/cut controls for tonal fine-tuning.   Featuring a unique circuit design, the MXR FET Driver captures the rich, creamy sound of an overdriven tube amplifier by cascading an op-amp gain stage into a FET stage. The FET Driver thickens up lead tones with musical, amp-like distortion and sustain without the fragility and inconsistency associated with tubes.