The Mad Professor Royal Blue, like the best boutique amps, lets you determine the amount of breakup by how hard you strike the strings with your pick, and/or by adjusting the volume knob on your guitar.
The Royal Blue can add this level of expressiveness to any clean or slightly overdriven amplifier.
Here's what Mad Professor have to say about this pedal
The Royal Blue overdrive is an extremely touch sensitive overdrive.
It offers wide range of tones from light overdrive into distortion and at lowest Distortion knob setting works as an EQ. It can also be used to create tube amp-like crunchy ‘strike hard for distortion’ effect. There is not much filtering on the overdrive, to provide transparent tone that you can tailor with both the Treble and Bass controls.
VOLUME: sets the overall output level of the pedal.
DISTORTION: controls distortion, for most dynamic response set where the amount of distortion is controllable with picking force.
TREBLE: a boost/cut “shelving” type equalizer that controls the amount of high end, operating where the Presence control is on most amplifiers. Treble can be used to add shimmer to even bright amplifiers without interfering with typical treble boost of most amplifiers.
BASS: a boost/cut shelving type equalizer that controls the low end, just above resonance of a standard 4×12 cabinet. With both Bass and Treble turned up, you can get a scooped heavy tone, turn the knobs down for soft mid-boost tone.