Kicker Boost

The Kicker is a DIY overdrive PCB project from GuitarPCB, sold under the NostalgiTone name, that recreates the Klon Centaur circuit. GuitarPCB's build document says it "captures the magic of the legendary Klon Centaur, delivering a rich harmonic boost, transparent overdrive"¹, and the product page repeats the claim that it "captures the magic of the legendary Klon Centaur"². Unlike a finished store-bought pedal, it arrives as a bare circuit board: you source the parts, solder them, and house the result yourself.

What you get, according to the maker, is the thing players chase the original Klon circuit for: a boost that adds depth and clarity without coloring your core tone. The build document describes "a transparent boost, rich harmonics, and dynamic touch sensitivity" that "adds depth and clarity without coloring your core tone"³.

A Klon Centaur-based boost

The Klon Centaur is one of the most copied overdrive circuits in guitar history, and the Kicker is GuitarPCB's take on it. The build document is direct about the lineage³²¹:

The product page frames the same thing in marketing terms, saying the pedal "captures the magic of the legendary Klon Centaur"².

GuitarPCB has built a small family of Klon-derived projects around this core:

The dual-combo projects are worth knowing about because they show how the Klon circuit is typically paired. The Blues Kicker build document says its Kicker section "recreates the articulate boost and midrange clarity of the legendary Klon-style circuit"⁴, and the John Mayer Tribute set describes the same section as delivering "the articulate boost and midrange clarity of the legendary Klon-style circuit"⁵. The companion section in both is a Marshall Bluesbreaker circuit, giving a two-in-one overdrive with a Klon-style voice on one side.

How the circuit works: dual RC4558 and a voltage doubler

The parts list in the build document names three ICs⁴:

• IC1: RC4558 dual op amp
• IC2: RC4558 dual op amp
• IC3: ICL7660S charge pump

That trio tells you most of what the circuit is doing.

The RC4558 is a dual op amp, so each package holds two amplification stages. Two of them give the circuit four op amp sections to work with, which is how a Klon-style design splits its jobs: input buffering, gain staging, tone shaping and output drive. The op amp choice matters to builders, since the RC4558 is the type associated with the original circuit's character⁴.

The ICL7660S is a charge pump, a small IC that converts one supply voltage into another. In boost and overdrive pedals, makers use this kind of internal voltage multiplying circuitry to raise the operating voltage above what a 9V input provides. MI Audio describes the same approach in its own products:

For a player, the practical effect is headroom: the circuit can push harder before the boost itself starts to break up, which is part of why Klon-style circuits are described as transparent rather than fuzzy or compressed.

The controls: Drive, Tone and Volume

The Kicker keeps the Klon circuit's three-knob format. The build document's parts list gives the pot values⁴:

The Drive control is the notable one for builders: it is specified as a dual pot, meaning two B100K potentiometers ganged on one shaft⁴. That is a parts-sourcing detail that matters, because a dual pot is not interchangeable with a standard single pot, and the Drive knob in a Klon-style circuit adjusts more than one gain-setting element at once.

The three-knob layout is shared by other Klon-style and overdrive projects across the market. GUP Tech's Dude Screamer, for example, uses Volume, Drive and Tone knobs in the same arrangement⁷, and Revv's Tilt Overdrive shapes its drive circuit with Treble, Bass, Volume and Gain knobs⁸. The Kicker's control set is the classic minimal trio: gain, tone, level.

How the Kicker differs from the alternatives

The Klon circuit has been reproduced in almost every form a product can take, and the Kicker sits in the DIY corner of that landscape. Comparing it with its neighbors shows what each approach offers.

The distinctions are practical ones. General Guitar Gadgets sells its replica as a full kit and PCB project, the same DIY territory as the Kicker, describing it plainly as "a replica of the Klon Centaur"⁹. Sonicake's Trio Rider is a finished pedal you can plug into, built around a modified version of the circuit¹⁰. HeadRush's K Drive is a digital stompbox model "Based on a Klon Centaur"¹¹, and Kemper's Drive effect for the Profiler is based on the Klon Centaur Gold¹², so both put the circuit inside modeling platforms rather than analog hardware. BLAMMO! Electronics takes yet another angle: its Utility Boost borrows only the buffer stage, with "the buffer option based on the popular Klon Centaur circuit"¹³.

For a player deciding between them, the trade is control versus convenience:

• A PCB project like the Kicker costs less in parts and lets you choose your own enclosure, switches and components, but you do the assembly.
• A production pedal like the Trio Rider works out of the box.
• A model gives you the circuit's behavior inside a multi-effect unit, with no analog signal path at all.

Using it in front of an amp

GuitarPCB positions the Kicker as more than a volume lift:

That is the classic boost-into-a-driven-amp technique: the pedal's gain and tone shaping firm up the low frequencies before the amp's own gain stage, so the distorted sound is tighter and more articulate.

The technique is not specific to Klon-style circuits, but the Kicker's description matches how players use boosts this way. Revv Amplification notes of its own Tilt Overdrive that "the Boost especially has been widely adopted by metal players for tightening high gain amps"⁸. The same logic applies to the Kicker's front-of-amp role: a midrange-forward, articulate boost into an amp that is already breaking up changes the character of the distortion as much as the volume.

Pedals on this page

KLON Centaur

Klon · Overdrive

$306 list price

GUP Tech Dude Screamer

GUP Tech · Overdrive

Revv Tilt

REVV · Boost

$169 list price

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