The Zap Master is a treble boost pedal from Portland's Blammo! Electronics, first reported in August 2021 as a Dallas Rangemaster treble boost clone1. It is Blammo!'s version of the classic Dallas Rangemaster treble boost circuit, built around a germanium transistor and described by the maker as a vintage germanium treble booster2. Delicious Audio called it "designed to sound and look like the original with a few modern upgrades"1.
A treble booster does what the name says: it lifts the high frequencies of the guitar signal and pushes the amp harder. As the DIY Fever technical analysis of the Rangemaster puts it, "having some sort of a treble booster at the front helps shape the sound of the guitar"3. Players historically used these pedals to make dark amps and humbucker guitars cut through, driving the amp's front end into earlier breakup.
Controls and the input cap switch
The control set is minimal: one Level knob and a 3-way toggle switch1. The toggle is an input capacitor switch that lets you choose between the stock value of 5nF or two additional mod values that let more bass into the audio path2. Delicious Audio describes it as a switch "that adjusts the amount of bass frequencies"1.
| Control | What it does |
|---|---|
| Level knob | Sets the amount of boost1 |
| 3-way input cap switch | Selects the stock 5nF input cap or two mod values that let more bass through2 |
The switch matters because the input capacitor is what defines a Rangemaster's character. The DIY Fever analysis of the original circuit shows the same idea as a common mod: an ON-OFF-ON toggle wired to switch between 5nF, 10nF and 15nF capacitors "for a wide range of sounds"3. At the stock value the pedal leans toward the treble-only behavior of the original; the other positions let more of the guitar's low end through for a fuller-range boost.
Germanium transistor and the two versions
The Zap Master comes in two versions. The standard version uses an NOS MP38a germanium transistor, while the OC44 version carries a NOS Mullard OC44 germanium transistor, the type most closely associated with the original Rangemaster, along with a voltage inverter and a DeMont 3PDT footswitch2.
One circuit change separates both versions from the original: Blammo! swapped the original PNP transistor style for an NPN type "to make powering and daisy chaining with other pedals simple"2. The original Rangemaster used a PNP germanium transistor with a positive ground, which is awkward on a modern pedalboard. The OC44 version solves the same problem differently, with a voltage inverter that allows the use of the standard center negative 9V supply rather than older center positive style plugs2.
Power and build
The pedal accepts the standard 2.1mm center negative power supply, Boss style2, so it runs from the same supply as most pedals on a board. Blammo! also adds a robust power filtering section with a reverse polarity protection diode, which helps guard the main circuit if an incorrect supply is connected1.
The build details:
- True bypass switching2
- Top mounted jacks for pedalboard-friendly layout1
- Hand screen printed enclosure1
- Reverse polarity protection diode1
The Dallas Rangemaster behind it
The circuit behind the Zap Master is the classic Dallas Rangemaster treble boost2. TONEHOME describes the Rangemaster as a treble booster, and Blammo! Electronics built the Zap Master to reproduce that circuit in a pedalboard-friendly pedal enclosure with top mounted jacks2.
Blammo! Electronics designed the Zap Master to sound and look like the original Rangemaster, with a few modern upgrades1. The main upgrade is a 3-way input cap switch that lets you choose between the stock value of 5nF or two additional mod values that let more bass into the audio path, so a player can shape how much of the low end the boost keeps2. The enclosure is hand screen printed, in keeping with the vintage look1.
That original design is why clones like the Zap Master exist at all: the circuit is simple, the parts are understood, and the sound it makes into a cranked amp is what players are after. The Zap Master's contribution is packaging that circuit with modern conveniences, standard power, true bypass, top jacks, and a bass switch the original never had12.
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Questions
Is the Blammo! Zap Master true bypass?
Yes. Blammo! Electronics lists true bypass for the Zap Master, and the OC44 version specifies true bypass with a DeMont 3PDT footswitch. When the pedal is off, the signal passes through without the circuit in the way.
What does the input cap switch do?
The 3-way toggle selects between the stock 5nF input capacitor value and two additional mod values that let more bass into the audio path. At the stock setting the pedal behaves like a classic treble booster; the other two positions open the door to fuller-range boost.
Does the Zap Master use a germanium or silicon transistor?
It uses germanium. The standard version carries an NOS MP38a germanium transistor, and a separate OC44 version uses an NOS Mullard OC44 germanium transistor, the type most associated with the original Dallas Rangemaster.
What power supply does the Zap Master take?
It accepts the standard 2.1mm center negative 9V supply, Boss style, so it works with common pedalboard power supplies and daisy chains. The OC44 version adds a voltage inverter so it also runs on center negative power rather than the older center positive style.
What is a Dallas Rangemaster?
A treble booster made by London's Dallas Musical Ltd in the 1960s, one of the first treble boosters guitarists used. Its germanium circuit shaped the signature tones of players such as Rory Gallagher, Tony Iommi and Marc Bolan, and it remains the template for modern treble booster pedals.
Sources (3)
- Blammo! Electronics Zap Master Treble Booster, Delicious Audio, 2021-08-17
- ZAP Master, BLAMMO! Electronics
- Effects > Dallas Rangemaster : DIY Fever, DIY Fever (diy-fever.com)