Dallas Rangemaster Treble Booster

The need for a treble booster arose in the mid-1960s, as British tube amplifiers such as the Vox AC30 or Marshall JTM45 tended to produce a slightly dark, muddy sound when overdriven, particularly when used with humbucking pickups.

Additionally, the vintage components in the Rangemaster circuitry could add characteristic distortion and overtones to color the guitar sound, much in the way of the more modern overdrive pedals.

[1] The unit is simple and consists of a grey folded metal casing with an on/off switch, a potentiometer controlling the boost setting, and in- and output jacks.

In Premier Guitar, Kenny Rardin describes his quest for one of the effects, which started with puzzlement over how Eric Clapton and Ritchie Blackmore achieved their tone; he spent years looking for a Rangemaster.

Other notable users whose sound depended heavily on the Rangemaster include Rory Gallagher, Brian May, Tony Iommi,[5] Marc Bolan and Billy Gibbons.