Dallas Rangemaster

Similarly to Brian May who uses his Deacy amp with a treble booster in front, I wanted to build something similar that can be used with my germanium radios converted into guitar amps. All those amplifier circuits in radios are designed to amplify wider range of frequencies and they expect lower impedance signal at the input, so plugging the guitar straight into the amplifier may not be ideal. As soon as you roll down the volume on guitar from 10 to 9, output volume drops significantly, because of the higher impedance of pickups. Having some sort of a treble booster at the front helps shape the sound of the guitar and reduces issues with impedance mismatch. I chose Rangemaster because it’s a legendary circuit and I have a bunch of germanium transistors that I could try and pick the one I like the most.


The circuit is very simple, but effective. It can pump out a respectable 24db boost in higher frequencies and push the amplifier into overdrive. Two components are crucial for the effect – input capacitor and transistor. Input capacitor forms a high pass filter and depending on the value it will let more or less of middle and lower frequencies.It’s best to experiment and find the right value for the particular guitar and or amp, but I found that anything above 22nF makes it less of a treble booster and more of a full range booster. Feel free to experiment with wider range of capacitance, but I recommend starting with values between 5nF and 15nF. The transistor should be a PNP Germanium (or even silicon). It affects boost level, but also the sound. Rangemaster is not a squeaky clean booster, it will overdrive when pushed hard and transistor will affect the character of overdrive. R.G. Keen from GeoFex.com wrote a great article dissecting the Rangemaster circuit. He recommends a low-leakage Germanium transistors with gains between 75 and 100. In addition to the choice of resistor by gain, we also need to worry about the bias. According to R.G. Keen, the best sounds can be had with collector voltage around -7V.


For more versatility, input capacitor can be omitted from the circuit board and placed on a switch, so we can have switchable capacitor values. One of many ways to accomplish this uses an ON-OFF-ON toggle switch with 5nF capacitor across the middle lugs. It’s always in the circuit. Outer lugs can have two capacitors that can be switched in parallel with the existing 5nF capacitor. Diagram below shows a setup that allows switching between 5nF, 10nF and 15nF capacitors for a wide range of sounds.


I drew a simple perfboard layout that can be used on 1×1″ protoboards that have 81 holes. It’s drawn with a trimmer for bias, although I put a fixed resistor in there and experimented with several transistors until I found the one that biases perfectly. Also, there’s room if you want to install sockets in parallel with input cap to add more capacitance and shift the frequency response curve to the left.


Being simple circuits, most boosters can be squeezed onto small boards, so I used one those awesome little 1×1″ proto boards with 3-per-pad plated-through holes. It’s very sturdy and easy to work with and I love using them for simple builds like this. I started from Dallas Rangemaster schematic and changed a few things – added socket in parallel with the input capacitor so I can add more capacitance and change the low-end/midrange response of the booster, replaced 47uF emitter capacitor with 22uF solid electrolytic (shouldn’t affect the sound, even 22uF is plenty), replaced the 10nF output capacitor with 22nF (there’s another input capacitor at the amp input, so I didn’t want to cut too much bass by having two capacitors in series).

As always, I used transistor socket to allow playing with different types of transistors and tried pretty much everything I had unfortunately, no OC44). The one I liked the most was GT308V that came out of the bin labeled 100-110hfe and gives a perfect collector voltage of -7V with stock biasing resistors.

25 Responses to “Dallas Rangemaster”
  1. Paul says:

    Thanks for publishing this!

    I am making a tagboard range master and want to do the input cap switch (slightly simpler on-on between a 5 and 10nf) and was wondering – do I need to run a ground wire from the switch? Or will it be okay as your image suggests – just wires running from and to the board?

    Thanks again for posting this!

  2. Joshua says:

    Monsieur Bancijka,

    Si’l vous-plaite, où est l’affichage LED sur votre schéma?

    Merci beaucoup,


    • bancika says:

      LED and bypass switch are not shown, they are standard true-bypass circuit together with the LED current-limiting resistor.

  3. Jay Urban says:

    I don’t see the LED anywhere on your schematic….. was that an afterthought that didn’t get included in your recao?

    • bancika says:

      Not an afterthought, LED is part of the bypass circuit that is not shown on the schematic for simplicity.

  4. Timothy Payne says:

    Why have you included a second 47mf cap with a 1meg resistor, when my treble booster kit only has one?

    • bancika says:

      I cannot possibly know why your kit has one. The second one filters input DC voltage when using a 9V adapter. If you use batteries you might not need it.

      • Timothy Payne says:

        Thanks for the tip, I don’t know why the kit didn’t come with the second cap in the first place! – Finally got mine working after a few attempts, (now where’s that resistor I left out…….)

  5. Olly says:

    When sourcing components such as capacitors, should the ‘max voltage’ just be >9v? Does it matter if the max voltage is much higher than that, e.g. 50v?
    Thanks for this awesome project.

    • bancika says:

      Yeah, any will do. However, higher voltage rating means bigger capacitor (and costs more), so it’s usually impractical to go to high across the board.

  6. Guido says:

    Hi Bancika! congratulations and thank you so much for this content:) I was wondering, how do you deal with the -9v power? do you require a specific power supply? thank you so much in advance

    • bancika says:

      Thanks for the comment, Guido. There are few ways you can get -9V:
      * 9V battery with – used as -9V and + used as ground (that’s what I do)
      * use isolated pedal power supply and then flip the polarity +9V
      * use +9V from any power supply and then use MAX1044 or similar charge pump circuit to get it to bipolar +-9V and then use the -9V from there, ignoring the +9V tap.

  7. Ralph says:

    I just wanted to say thank you for taking the time posting all your “hobby projects” here on your website. I’ve been trying to gather information in amp building/modding and pedal building/modding for months hoping to teach myself or learn from people such as yourself. I can’t begin to tell you how grateful I am to have found your website. Many of your projects are exactly the same ones I’ve been interested in learning about and hopefully building myself someday. Also, it’s very cool that you respond to people’s comments and questions. Thank you

    • bancika says:

      You are very welcome. This site stands as my thanks to the online community that has taught me everything I know.

  8. Julian says:

    Yeah removing the 9V battery and power it by the jack cable directmy plugged into the amp .

    If this not possible, can you tell me where I need to solder the black cable of the battery. There’s no indication for that on the schematic


  9. Julian says:

    First let me tell you that is a really good job !
    You have to sell ’em !

    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 .

    Thanks a lot if you answer to that 😁

  10. Valentin Collado says:

    Nice but, did you have a sound sample to hear what it sounds like ? And I found a oc44n does it will works ?

    Thanks for your time and attention.

    • bancika says:

      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.

      • Valentin Collado says:

        Ho i didn’t know that !
        Nut I searched on internet for schematic but yours is very different from all others that I found .
        I didn’t know if it will function :/ .

        You said earlier that you changed a lot of things . So i’m not very sure :/ .

        Have sound sample for me please ?

        Thanks for reading this message.

      • Valentin Collado says:

        And by the way can you answer to that please?

        I modified the picture of the schematic to see if that can be possible


  11. Craig says:

    Nice job, do you sell these units by chance. I am interested.

    Thanks, Craig

    • bancika says:

      thanks for the comment. Unfortunately, I don’t have time and resources to turn this hobby into a business. I only build for myself and sometimes sell stuff that I get bored with to make room for new builds 🙂

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    The idea behind this site is to share my experience with Do It Yourself approach to guitars, amplifiers and pedals. Whether you want to save a couple of bucks by performing a mod or upgrade yourself instead of paying a tech, or want to build your own piece of gear from scratch, I'm sure you will find something interesting here. Also, this is the home of DIY Layout Creator, a free piece of software for drawing circuit layouts and schematics, written with DIY enthusiasts in mind.