5KR (Five-Knob Rangemaster) Boost

The 5KR (Five-Knob Rangemaster) is a single-transistor germanium boost that goes from full-range sparkly volume lift to nasty, cutting, higher-gain-than-vintage treble boost and every shade in between, with outstanding volume knob cleanup.


B – Bass. Rangemaster setting: minimum.

P – Presence (i.e. input impedance). Rangemaster setting: minimum.

S – Symmetry. The transistor base of a Rangemaster is biased to produce an asymmetric output waveform. This control provides flexibility on both sides of the classic sound, from gated and broken counter-clockwise to fuller and cleaner clockwise. Rangemaster setting: noon.

(Presence and Symmetry interact slightly; increasing/decreasing Symmetry also increases/decreases Presence a bit. Changing Presence does not change Symmetry. It is a one-way interaction.)

G – Gain. Rangemaster setting: typically 2 – 3 o’clock.

V – Volume

I – Input

O – Output

Power – Standard Boss/Ibanez 9V C-. It’s daisychain-able!

The insides of a 5KR

The input capacitor that puts the “treble” in treble boost is socketed so you can easily adjust its value. 5KRs ship with a 3.3 nF cap to best replicate the frequency response of a classic Rangemaster. If you run your 5KR with the gain above 3 o’clock you might prefer a smaller cap if you’re not getting enough bite; conversely, if you run the gain below noon or so you might like a bigger cap for a better blend with the bass control. (If you run the bass control all the way up, the treble cap doesn’t matter!)

The Presence control is subtle with your instrument volume all the way up, but more noticeable as you turn the instrument down. With Presence up high you’ll retain more treble as you turn your instrument down; really nice for you “use your volume knob!” types out there.