The Dallas Rangemaster Treble Booster is a booster guitar pedal that especially emphasizes the upper mid and treble frequencies (coloring the signal). It was designed in London (UK) by Dallas Musical Ltd in 1965. At that time, the British tube amplifiers such as the Vox AC30 or Marshall JTM45, tended to produce a slightly dark, muddy tones when overdriven, this box fixed that issue. The effect became popular because of its sweet coloration, slightly bending the signal and giving a soft compression when maxed out.
- excerpt from electrosmash.com