The GoudieFX 808+ is clone of the ever popular (or infamous) Tube Screamer, the sound of this pedal is so popular that I left the frequency response and filters as they are (LPF/HPF right at 723Hz for that characteristic TS mid range honk). However, I did add the less/more mod, the mod doesn't affect the tone or frequency response but provides less gain at minimum settings (4 vs. 10) and twice the gain at maximum drive settings (200 vs. 100). This mod makes the pedal much more versatile allowing you to cover cleaner and more overdriven sounds without changing the signature sound of the 808, hence the 808 "plus" you get the classic tube screamer sound with less/more gain if you want to use it.