The charge pump lets the op-amp run with more headroom and allows for more quiet operation. The original RAT is known for a specific frequency response do to the inability of its IC to amplify quickly. Instead of chasing unicorns, the Backstabber uses filtering to emulate the frequency response. We are using a more modern IC which results in RAT-like tones that are tighter and more responsive. Original signal is run through a highhead overdrive cirucit, Which can be used as a traditional clean blend, or parallel overdrive.