Rangemaster

From the post

The Dallas Rangemaster was one of the earliest guitar effects. Originally built into an amp-top box, the Rangemaster was often used in an “always-on” fashion, contributing heavily to the trademark sounds of both Brian May and Tony Iommi. It is a favorite of many for driving the input of a tube amp. The Rangemaster boosts the treble of the signal by filtering out some of the low end via an input high pass filter and then boosting the resulting signal with a simple common-emitter transistor gain stage. The input high pass filter is formed by the 5nF capacitor and the input impedance of the transistor in parallel with 470k and 68k. A common modification made on modern Rangemaster builds is to have various input capacitor values on a switch so the user can move the cutoff frequency of the filter, allowing for a more full-range boost or one with even more lows cut. It is a good component to experiment with to see what you like there. 1M pull-down resistors have been added to the input and output of the effect. These are present to prevent the pedal from popping or clicking when the effect is engaged. In original units, it was not a concern given that they were not meant to be toggled mid-song, but rather kept either engaged or disengaged. When using the effect in a modern true bypass pedal, they may be desirable. If you’d prefer to keep the circuit original, both 1M resistors can be left out. This is a PNP build and uses battery power only. With no LED indicator, this pedal will last a very long time on battery power. If you would like to build this pedal with a DC jack, please see our PNP "Positive Ground" Pedal Considerations tech article. See Figure 4 in our Guitar Pedal Footswitch and Jack Wiring article for the recommended footswitch and I/O wiring.