AXP has released CharBooster a new free VST plug-in, a guitar booster effect, with a character. It allows to shape, overdrive and boost the guitar signal before hitting your favorite amplifier VST plug-in. The effect is based on the 12ax7 tube preamp and the ATR-102 tape recorder models.
CharBooster is a composite overdrive effect tailored specifically to be used as booster in front of any virtual amplifier model. It essentially consists of a pre-emphasis filter section designed to provide a variation of voicings for your instrument followed by a saturation circuit that excites the signal with harmonics while still being as transparent as possible. The UI is not trying to look like a hardware stomp box but rather has a range of meters and scopes to provide an insight on what is going on with your signal.
CharBooster is available for free as a VST plug-in for 32/64-bit Windows at AXP SoftAmp.