In the image below you can see the output signal with different Vb values when the Volume knob is maxed out:. But part of the character and mojo of this pedal remains on its biasing. The simplicity of the circuit makes builders experiment adding some extra features so players can have some more knobs and switches to play with.
There are 4 ways to ground the Rangemaster circuit:. The Dallas Rangemaster Input Cap modification is the most popular one. By simply changing the C1 input cap we can transform the frequency response making it more limited or wide. This modification is not as popular as the Input Cap Mod and for a reason. Although it has to be admitted that 10nF is a low value for an output cap many pedals use caps in the nF to 47uF range for this.
Users have different setups or "loads" so the result is variable. You can get more info about this is the Bias Section. My sincere appreciation to J.
Blake Arnold for your help with this analysis. Thanks for reading, all feedback is appreciated: This email address is being protected from spambots. You need JavaScript enabled to view it. Some Rights Reserved , you are free to copy, share, remix and use all material. Trademarks, brand names and logos are the property of their respective owners.
Table of Contents. These vintage resistors could bring more organic sound but also are blamed to bring the noise. For other vintage effects like the Fuzz Face that noisy by definition , carbon comp resistors are a great choice adding a bit more noise to a high gain fuzz wont hurt anyone.
On the other hand, for a booster like the Rangemaster maybe carbon comp technology is not a good idea you want to keep all as clean as possible , so modern film resistors are a better choice. The potentiometer: The original Dallas Rangemaster uses a UK Welwyn 10k ohm sometimes 20k unit with two mounting screws. The potentiometer body was made of bakelite and isolated from the chassis, but this feature does not add any benefit for the pedal. The original Germanium transistor was the Mullard OC44, long time ago discontinued.
They are claimed to sound good with a soft clipping knee but also noisy, microphonic, temperature dependent and gain variable. Capacitors: There is not much magic involved on the caps, they are just common available technologies: 47uF is aluminum electrolytic, de 5nF and 10nF are films.
The circuit is beautifully simple, a single stage Common Emitter PNP amplifier: C1: Is the series 5nF input cap, it will remove any DC level from the input signal and also create a high-pass filter together with R1, R2 and the input impedance of the Q1 transistor. This cap is crucial for the pedal equalization. You can read about this filter in the Frequency Response section and also in the Mods part.
They provide the required bias voltage to the base of the transistor and define the operating point of the pedal. RV: Is an audio logarithmic 10K potentiometer. It will control the amount of volume of gain applied to the input signal, check the Voltage Gain section for more info.
R3: is a 3. C3: 47uF electrolytic cap, makes the guitar signal to bypass the R3 resistor. This makes the signal to get higher gain despite the bias point established by R3.
C2: it is the 10nF output series capacitor. Its task is to clean any DC for the output signal. C4: The power supply is simply formed by a single 47uF, there is no protection against reverse polarity connections but makes sense because the original effect was designed to work only on battery. This is why many people like to place this effect the first in the pedalboard or keeping it in an isolated loop 2.
This is not necessarily a good or a bad thing, but the Rangemaster will for sure be able to drive signals harder. This means that the sound will scratch and whenever the volume is touched even if you use the original plastic- non-conductive original discontinued Wilk potentiometers 2. The transistor amplifier is not at the center of the linear region, and it will result in an asymmetric soft clipping: When the Vol control is maxed out, the signal will be boosted and also driven into soft clipping, this will color the signal and make the sound quite particular.
As a result of that the bias point of the pedal will change from one unit to another, to fix that and try to make the best sound out of the pedal we have two options: Find the germanium transistor with the perfect HFE gain Any value between 75 and would be great.
The problem is that germanium transistors went out of fashion 30 years ago, there are no lines of production and finding NOS batches with a decent gain is almost impossible. In the '60s this was a viable option, nowadays not so much. Bias the circuit properly: When Dallas designed the Rangemaster, they probably had access to good transistors with controlled gain, so they just set a pair of fixed resistors R1 and R2.
Now that the transistors are not so numerous, we can just adjust this 2 resistors and make the pedal sound its best. The sound of the Rangemaster is heavily dependant on the bias point. Usually, transistors are biased to the middle of their swing area so they can produce the biggest non-distorted output signal maximum headroom. This is not the case of the Rangemaster, where the bias is a bit off the center creating an asymmetric gain. The Perfect Bias point: It is commonly agreed that the ideal bias point for the Dallas Rangemaster Treble Booster is to have Q1 collector voltage at The original box never faced this issue because it only works on batteries.
Thanks for the comment, Guido. Thank you. You are very welcome. This site stands as my thanks to the online community that has taught me everything I know.
If this not possible, can you tell me where I need to solder the black cable of the battery. Hello, First let me tell you that is a really good job! And by the way I wanted to see if I can remove the 9volts battery of the system and at the output directly solder a Jack cable that directly going to the amp and if that gonna be function.
Nice but, did you have a sound sample to hear what it sounds like? And I found a oc44n does it will works? Hi with those old transistors you really have to try and see as they are all over the place with the specs. Gain and leakage may or may not be good enough. Ideally, try a handful of transistors and pick the one you like. Nut I searched on internet for schematic but yours is very different from all others that I found.
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