Klon Centaur and clones and fake components

The legend of the Klon Centaur guitar distortion effect pedal, which debuted in the mid-’90s, has taken on a life of its own as one of the most collectable effects pedals of all time. It got fame because it was used and liked by such players as John Mayer, Nels Cline and Joe Perry (to name just a few). Its relative scarcity on the used market have propelled prices to unprecedented levels.

Image source: Wikipedia

The Klon Centaur is an overdrive pedal made by the American engineer Bill Finnegan between 1994 and 2008. Finnegan hoped to create a pedal that would recreate the harmonically rich distortion of a guitar amplifier at a high volume. Bill Finnegan sought an overdrive pedal that would recreate the harmonically rich distortion of a guitar amplifier at a high volume. He wanted a “big, open” sound, with a “hint of tube clipping”, that would not sound like a pedal was being used. He selected germanium diodes for the circuit and purchased as many as he could afford.

The Klon Centaur has been used by guitarists including Jeff Beck, John Mayer, Joe Perry (of Aerosmith), Nels Cline (of Wilco), Matt Schofield and Ed O’Brien (of Radiohead). When Klon Centaur became a very much wanted product, Finnegan struggled to meet demand and he discontinued the Centaur in 2008 (redesigned it in 2014 as the Klon KTR). During that time only around 8,000 were built. This has lead the used units sold for very much inflated prices. The Klon Centaur is one of those mythical pedals that price wise has now gone through the roof. This pedal is currently fetching sometimes over $5000 on the secondhand market.

The Klon Centaur has also inspired numerous clones by different manufacturers. Basically it’s almost like all pedals are made out of the same inexpensive resistors, capacitors, transistors and integrated circuits. Original designer Finnegan expressed skepticism that they could replicate the sound, due to factors including the rarity of the Centaur’s germanium diodes.

In early 2023, Josh Scott, the owner of JHS Pedals, published a YouTube video comparing the Centaur against the DigiTech Bad Monkey Tube Overdrive, a discontinued pedal released in 2004. The video demonstrated no discernible difference in sound. Soon the listings prices for Bad Monkey pedals rose very much.

The Klon: A Short History, featuring Jeff McErlain

Klon Centaur – Is This Overdrive Pedal Really Worth $5000?

The $5,000 Guitar Pedal RIPOFF… what have I DONE?

Let’s look what makes the Klon Centaur what it is. Let’s take a look at the circuit in it.

Klon KTR Teardown! See what’s inside!

Welcome back to the teardown series, where I take apart new and interesting pedals, and show you what’s going on inside!
This week is the famous Klon KTR, a pedal-friendly remake of the Klon Centaur.

Klon Centaur Analysis

The Klon Centaur in an overdrive guitar pedal designed by Bill Finnegan with the help of 2 MIT Electronic Engineers between 1990 and 1994. The initial idea was to improve the TubeScreamer transient response and the midrange-bass frequencies in order to create a big open sound with a hint of tube clipping: the so-called transparent overdrive.

The design process took more than 4 years and the result was a mythic $329 hand build pedal that was running in production for 15 years. Nowadays the original models are highly appreciated

Source: https://www.electrosmash.com/images/tech/klon-centaur/Klon-Centaur-Schematic-Parts.png

The circuit is quite original, showing a mix of academic electronic design together with pure experimental/think-out-of-the-box blocks. The development process was based on long listening tests, trying different resistors & caps values and listening to the sound variation, this is why the bill of materials has so many references and tricky values.

The op-amp used is simple TL072, proving that for a great sounding guitar pedal no exotic/mojo/expensive parts are needed, just pure and smart electronic design.

The circuit uses a single layer PCB with standard through-hole components. In the parts of the circuit where double side PCB are needed (tracks crossing), there are links (wired bridges) that make the manufacture easier and cheaper. However, all the potentiometers, jacks and the battery are wired and hand soldered to the PCB which makes it quite labor intensive.

This PCB is famous for being covered with black epoxy resin (gooped) in order to prevent people from replicating it.

During its 15 years of production, the Klon enclosure and circuit had some variations in color and graphics, but in theory, the minimal variations between the years do not affect the sound. In all of them the Germanium Clipping Diodes were the important detail.

According to Bill Finnegan (Klon Centaur Designer), the type of diodes used in the Op-Amp Stage make a great difference in the sound:

“These diodes are the most important factor in how the circuit sounds when it’s being used to create distortion”

“I have always used a germanium diode with the part number 1N34A, but you should understand that this particular part has since the 1950s or so been manufactured by literally hundreds of different companies, and having listened to as many different ones as I have, I can say with confidence that they all sound somewhat different in my circuit, and often they sound VERY different.”

The clipping diodes define the distortion sound signature, it is built using 2 back to back diodes that shunt the signal to ground, this clipping method gives a hard-clipping sound also used in many other pedals (MXR Distortion+, RAT and Boss-DS1).

The 1N34A germanium diodes have a forward voltage VF=0.35 which is quite low compared to silicon diodes that usually have 0.7V drop, resulting in a harder compression of the signal.

Klon Centaur circuit analysis

Finally, the remaining signal goes to the input of the second OP amp. A GAIN1 potentiometer set the amount of signal going into the amplification loop of the OP amp. GAIN1 and GAIN2 are in fact one double potentiometer: when the value of one increase, the other one increase! Thus, it doses the amount of clean and saturated signal to mix together: the more saturated signal, the less clean signal! It is an unique feature that is not present in any other pedal, and this is one of the novelty brung by the Klon Centaur: a part of the signal is kept as is, and the other part is saturated. Thus, the overdrive is really good for low drive.

The saturation comes mainly from the OP amp saturation. Another thing that is not usual with classic overdrives circuits! It has quit a high gain. We can calculate it. It is wired in non-inverter, so the gain will be 1 + loop resistor / resistor to ground = 1 + 422 / (15 + 2 + value of the 100k potentiometer = 1 + 422 / (117) = 4,6 with the lowest gain, and 1 + 422 / (17) = 25,8 when gain is maxed.

Then, there is a coupling capacitor (C9), and signal arrives towards the famous germanium diodes D2/D3. Most of the times, with moderate gain, these diodes are useless! I could test that with my soul food mod. They only are important when the gain is set up pretty high.

Deep Dive! All About the Klon Centaur Germanium Clipping Diodes!

The venerable Klon Centaur has invaded just about everyone’s pedalboard in one form or another, but are those famous germanium clipping diodes really the “magic” that makes the Centaur so popular
0:00 – Intro
2:18 – Part 1: History of the Klon Centaur
2:57 – Bill Finnegan, designing and selling the Centaur
6:40 – FSB trace of S698
10:32 – Schematic released, Klon Centaur stops production, KTR
12:31 – Significance of Klon diodes
15:47 – Part 2: Diodes, basic electrical characteristics
19:04 – Forward voltage curves
22:09 – What we know about the Klon Centaur diodes
24:19 – How Finnegan chose the diodes
25:02 – forward voltage discrepancies
30:53 – Klon diode replacements
35:54 – Finnegan is running out of the original diode
37:53 – Part 3: Clean Boost Mode?
40:52 – Listening test intro
42:28 – Beginning of listening test
45:57 – Oscilloscope test intro
47:35 – Beginning of o-scope test
51:26 – Outro

Klon Centaur Clipping Diodes Pt.2: Curve Tracing

Klon Centaurs can now cost $5000, why not try a commercial clone pedal or build your own and save a buck or two… The Klon Centaur is an iconic guitar pedal with countless clones and imitations. You can even buy a cheap kit to build your own clone. Can he tell the difference between an $8000 Klon, and a $40 Klone? Probably not. Here are links to videos comparing and original Klon Centaur agains different clone versions:

Klon vs Klone – Don’t Make The Same Mistake I Did!

$7K Klon V.S. $30 Clone (Can You Hear It? Ep. 1)

The Klon Clone Wars: Revenge of the Wish. An Original Klon Centaur Vs The Wish Klon Centaur Klone

Klon Centaur vs. Ceriatone Centura vs. KTR (and diodes!)

Bad Monkey vs KLON, JHS Morning Glory, Zendrive, Fulldrive, and ODR-1

Klon Centaur, KTR, Centura, and Archer – side by side!

How Close Are They REALLY? Klon Centaur VS. Ceriatone Centura VS. J. Rockett Archer Ikon

Ceriatone Centura Teardown! See what’s inside! (a very convincing Klon Centaur clone)

What no one tells you about Guitar Pedals & “clone” circuits

I built the KLON CENTAUR Kit from StewMac: Is it any Good?

How to Build a Klon Centaur Clone From a Kit (Step-by-Step Tutorial)
How to Build a Klon Centaur Clone (DIY Kit Tutorial)

How Much Tone Is In The Diode? Germanium Diode Shootout – Overdrive Tone Comparing 9 Japanese Diodes

Today we are comparing 9 germanium diodes in a hard clipping overdrive circuit to see if we can find the “special one,” or if there is any difference at all to begin with. This is just a fun comparison born out of simple curiosity and my love for experimentation.

The diodes are all NOS vintage Japanese germanium diodes. I took several samples from each batch, measured their forward voltages, and chose the pair with the most in-between average value. With a range from 0.27v to 0.49v, I think this represents a good spread for testing tonal variations.

When getting the components to buid your own guitar pedals, keep in mind that the Chinese sellers fake really every kind of semiconductor: Germanium diodes, small-signal FETs, radio-ICs, schottky-diodes… So if you get component from there, you should test them before installing the to circuit. For Germanium diodes first test to see if the “Germanium” diodes you bought online are real Germanium, and not fake silicon Schottky diodes, is to test the reverse current: Germanium diodes have reverse leakage currents. Schottky diodes have little to no leakage at small voltages. Lastly remember NOS Germanium diodes are getting hard to find and there really is no such thing as cheap Germanium.

Test for Real Germanium Diode or Fake Schottky imports from China

Some Fake Chinese Semiconductors

GuitarPCB Germanium Diode Tutorial – Real or Not?

1N34A or NOT 1N34A ???


  1. Tomi Engdahl says:

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  2. Tomi Engdahl says:

    Test for Real Germanium Diode or Fake Schottky imports from China

    This is a limited, but good first test to see if the “Germanium” diodes you bought online are real Germanium, and not fake silicon Schottky diodes.
    Test: Germanium diodes have reverse leakage currents.
    Schottky diodes have little to no leakage at small voltages.
    Important for guitar pedals, radio, etc.

    NOTE: A 9v battery works the same, and shows more reverse leakage, in case your meter is not super sensitive in the micro-amp (μA) range. (Thx KJ6EAD). For the record, this meter was $29 at Harbor Freight. Not super accurate or robust, but it was sensitive enough for this demonstration.

  3. Tomi Engdahl says:

    How Much Tone Is In The Diodes? Comparing Silicon VS Germanium VS LED In A Hard Clipping Overdrive

  4. Tomi Engdahl says:

    Understanding Distortion (Pt2) – Diode Clipping circuits

  5. Tomi Engdahl says:

    Test different clipping modes for diy pedals

    00:18 Clean
    00:31 1N4148
    00:44 1N4001
    00:56 1N34A
    01:10 1N4148+1N34A
    01:23 1N34A+Red led
    01:36 Red Led
    01:49 yellow led
    02:02 1N4148+yellow led
    02:17 1N4148+1N4001+1N4001

    00:10 Clean
    00:22 1N4148
    00:35 1N4001
    00:48 1N34A
    01:00 1N4148+1N34A
    01:14 1N34A+Red led
    01:28 Red Led
    01:40 yellow led
    01:53 1N4148+yellow led
    02:07 1N4148+1N4001+1N4001

  6. Tomi Engdahl says:

    GuitarPCB Germanium Diode Tutorial – Real or Not?

  7. Tomi Engdahl says:

    You Can Use An Old Tape Deck As A Distortion Pedal

    Distorted guitars were a big part of the rock revolution last century; we try to forget about the roll. As a youth, [David Hilowitz] couldn’t afford a loud aggressive amp, a distortion pedal, or even a proper electric guitar. This experience ended up teaching him that you can use random old audio hardware as a distortion effect.

    [David’s] guitar journey started when he found a classical guitar on a dumpster. He learned to play, but longed for the sound of a proper electric guitar. Family friends gifted him a solitary pickup, intending he build a guitar, but he simply duct-taped it to his steel-strung classical instead. The only thing he lacked was an amp. He made do with an old stereo system and a record pre-amp. With his his faux-electric guitar plugged into the microphone input, he was blessed with a rudimentary but pleasant distortion that filled his heart with joy.



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