Tru-Fi Treble Boost Rangemaster

The Tru-Fi Treble Boost Rangemaster is a boost pedal built in the image of the Dallas Rangemaster, the 1960s treble booster that shaped the sound of British rock guitar. Tru-Fi describes it as a pedal that "takes a mild overdriven tube guitar amp and push's it into outer space for the classic Crunch Rock sound," and names Brian May of Queen, Sabbath and Deep Purple as players associated with that Rangemaster approach¹². The pedal is built with real OC44 Mullard Black Glass transistors, the germanium part at the heart of the original circuit¹.

What it does to your sound

A treble booster sits between the guitar and the amp and does two things at once. The British Pedal Company, describing the original Dallas unit, puts it plainly: "Its function was two-fold: to increase the signal strength of the guitar going into the amplifier, and to increase tones"³. In practice that means the pedal pushes more signal, weighted toward the top end, into an already working tube amp, and the amp's own overdrive does the rest. That is the classic use: a cranked amp on the edge of breakup, treble boost in front, and the sound turns into sustained crunch. MusicRadar's Trevor Curwen called the Rangemaster treble boost "one favourite" for giving an amp extra lift, from a time before dedicated stompbox boosts were common⁴.

Controls

The front panel carries a switch and a knob, and the switch is where the Tru-Fi departs from the original¹:

Tru-Fi's own verdict on the layout: "Every position on the switch is incredibly usable and the boost knob is very responsive."¹

On the original Dallas unit, the switch really was a simple ON/OFF sliding switch, with a potentiometer to adjust the volume². The tri-mode frequency selection on the Tru-Fi echoes a well-known Rangemaster modification: GuitarPCB's circuit analysis describes an output cap mod using an ON-OFF-ON switch to change between 1nF, 10nF (the standard value) and 1uF, which shifts the frequency character of the boost². The Tru-Fi builds that idea in from the factory.

The circuit it comes from

The Dallas Rangemaster Treble Booster is, in GuitarPCB's words, "beautifully simple, a single stage Common Emitter PNP amplifier"². Their analysis puts its voltage gain at 80, equal to 38dB². It was designed with the parts available in the 1960s, including carbon comp resistors and Mullard germanium transistors². Vintage Guitar magazine reports that most Rangemasters carried a Mullard OC44 or an NTK275, the transistor also used in the original Dallas Arbiter Fuzz Face, although some boards used a Mullard OC71⁵. The Tru-Fi's choice of real OC44 Mullard Black Glass transistors follows the most common original specification¹⁵.

The original was made by Dallas, and the circuit's association with JMI lives on: TONEHOME lists a JMI Rangemaster Treble Booster re-issue, hand-built in England, limited to 100 units and powered by NOS OC44 transistors, dated England 2012⁶. The circuit has been copied and varied many times since, and germanium Rangemaster-style boosts remain a recognized category among boost pedals.

Questions