Revisiting my Rangemaster Vintage Treble Booster pedal.

[DrNomis_44]

Hi everyone,

I thought that I would start another revisit thread, but this time it is going to be about my DIY Rangemaster Vintage Treble Booster pedal.

First of all, I'll post a couple of pics of it, and then I'm going to do a write-up about it which will include a description of what it is, some history, and how you can actually make one for yourself, there will also be a demo so you can hear what it sounds like and what it does.....stay tuned.


Here we go:


Outside:




And Inside:




So, what is a Rangemaster Treble Booster and what does it do?, the Rangemaster Treble Booster is a very simple, one-Transistor, booster pedal which has been deliberately designed to boost the treble-frequencies, or highs, when used with an electric guitar, it was originally intended for use with dark-sounding guitar amps to give them more "presence", but, guitarists soon learned that you could use it to push an already distorting amp into heavier distortion, now normally if you were to do this with a typical valve guitar amp, you would notice that along with the heavier distortion, the sound would get a bit muddy in the bass, or low frequencies, since the Rangemaster only boosts the treble frequencies, this prevents the low frequencies from becoming too muddy, I've actually experimented a bit with my Rangemaster pedal and I noticed that it does indeed do that, but there's a bit of a midrangey-ness to the sound that I actually quite like, reminds me of a lot of those old vintage guitar sounds from the 60's and 70's.


Here's a wikipedia webpage about the Rangemaster Treble Booster:

https://en.wikipedia.org/wiki/Dallas...Treble_Booster


And here's what a real vintage Rangemaster looked like:

https://www.vintageguitar.com/20424/...s-rangemaster/


That second link also has a pic of the insides of it, showing just how simple it is.

And here's the actual circuit diagram for my Rangemaster pedal, as I built it:




The circuit for my Rangemaster pedal is basically the same as for a vintage Rangemaster, except for a few minor differences, firstly, I've used an AC128 PNP Germanium Transistor because good vintage OC44's are getting a bit hard to find, and expensive when you can find them, secondly, I added a blue Led indicator and 3PDT Footswitch (the original used a slider-switch), and thirdly I added R1 and R5 (1M resistors) to eliminate popping-noises when you stomp on the Footswitch (they don't have any audible effect on the sound).

While looking at the circuit diagram I posted, you might notice that it has been drawn so that the circuit ground is positive rather than negative, this is because the AC128 Transistor I'm using is a PNP type rather than an NPN, back in about the mid 40's when Transistors were first invented by scientists working at Bell Labs, the whole point was to come up with a more reliable, efficient, and compact replacement for the Valve Technology which was current at the time, it was specifically intended to replace Valve Technology used in Telephone applications, the only semiconductor material they had available at the time was the element called Germanium, Silicon Transistor Technology wouldn't arrive till later, a lot of those early Germanium Transistors actually weren't all that good even when brand new, some worked while others barely worked at all, but improvements were made in Germanium Transistor Technology during the 50's and 60's, at first only PNP Germanium Transistors were made because it was difficult to make reliable NPN types, as it just so happens the manufacturers of the original Dallas Rangemaster had to use whatever was cheaply available to them.

The letters PNP and NPN indicate the polarity of the three semiconductor layers that form a Transistor, "P" indicates that the layer is Positive, while "N" indicates that the layer is Negative, so for a PNP Transistor the "E" (Emitter) layer is Positive, the "B" (Base) layer is Negative, and the "C" (Collector) layer is Positive, now in order for a PNP Transistor to work correctly in the Rangemaster circuit, the Emitter layer needs to be connected to a Positive ground.