Clown Centurion

From the vendor

Clown Centurion

May 30, 2022 6 min read

Updated: Aug 22, 2022

I like to take circuits I find interesting and rework them according to my taste, following some guidelines, which can be summed up as:

• reducing the number of components as much as possible. I think there's beauty and elegance in simple things, and if I can get away with it or have a good reason to, I like to use less components;

• standard values. I like to stick to E6 values for the same reasons, and also for accessibility, if I can. Call it a challenge, but if I can get to the same results sticking to standard values, and you usually can, even for the half of the values or less that are actually relevant, so other than the ones that are "plenty big". If the accuracy penalty is too big though, I don't;

• noise. I like to apply simple concepts like low impedance design and avoiding attenuation before amplification to improve noise performance. Noise is usually neglected in guitar pedals, but with the high gains sometimes involved, I don't see why that should be the case if it can be helped;

• faithfulness. Before all the rest, I strive to keep the circuit sounding as it is unless I have a good reason. People like the sound of these circuits, and I'm not here to argue with that, just to suggest a different way to get to the same goal. This means same gain over headroom and frequency response throughout.

So, the Klon. This isn't addressed to people for which only the original will do, or only an exact copy, I don't wanna argue with those. This is for everyone else who like the sound of the pedal or new circuits. I also have some interesting insights I've collected on the circuit though, and some circuit analysis sprinkled throughout.

Let's go step by step:

• Input stage. This is just a buffer, nothing to see here, although the input resistor (maybe ESD protection) was removed according to all the points above.

• The three branches. This is the tricky part. As some might know, the effected signal is a mix of three paths by the U2A summing amplifier, with a dual gang pot controlling gain of two of them. Well, that's only part of the story, as I found that R3 and C4 (in my schem) also form and high pass filter with C2 for the clipping path! Of course there's also clean attenuated signal tapped off there by R5, and this part is mostly unchanged, except for R3 being a standard value. Here's the FR of the top branch:

• The bottom branch. This one carries clean signal of which the volume is adjusted by half of the gain pot. In the original, the signal to the gain pot comes from a fixed attenuator formed by a 5.1K and a 1.5K resistor, to which are added a 68n shelving highpass (bright cap) and a shelving lowpass cap. After the volume, the signal goes again through a shelving lowpass formed by the 27K in parallel with the 12K and 27n into the summing amp. In parallel to this there's a 22K and a 2.2n. Unlike the other one, this network is not at virtual ground and its output isn't s