Email: th@thallenbeck.com
I’ve been building a lot of pedal clones lately so here is… another clone, of the Colorsound One-Knob Fuzz pedal, visible above in all its bare-aluminum glory. From what I can tell, the original Colorsound pedal was a big ol’ thing almost the size of a wah pedal, with a footswitch and, you guessed it, one knob, which controlled output volume.
Here is a Gear Page thread about the Colorsound One-Knob Fuzz:
https://www.thegearpage.net/board/index.php?threads/colorsound-single-knob-fuzz-box.1223554
And I found this:
https://www.macaris.co.uk/colorsound/one-knob-fuzz
And, here is the action-packed one-minute-and-thirty-nine-second video I made for the doodad that I made:
Below is a link to the schematic I used for reference, from the Beavis Audio website, which is so badass that it doesn’t seem to have an SSL certificate:
http://beavisaudio.com/schematics/Colorsound-One-Knob-Fuzz-Schematic.htm
… and here is my version:
Referring to the schematic above:
A “traditional” FF would tend to have adjustable resistance (a pot) in the vicinity of R6 and C3 to control the gain, but for this one, it’s pegged at max. Oh, you wanted dulcet low-gain subtlety? Why look, there’s a bus leaving for Namby-Pamby-Land right now that might have an extra seat for ya, there, Casper Milquetoast!
The schematics I’ve seen for this unit, including the Beavis Audio schematic, don’t have a resistor at R1. I put one in because… I could. And because I’m accustomed to seeing something like that at the input of a dirtbox. Does it change the sound? I don’t know. Am I going to build another unit without R1 for comparison? Probably not, because I’m too lazy and it doesn’t matter anyway.
Note that R3 is 150 kOhms, instead of the oft-seen value of 100 kOhms for feedback between Q2 and Q1. The (relatively) increased resistance gives the circuit some extra “squish”, or compression (?) that manifests as an awkward spitty-ness when the signal dies off. That is audible at the very end of the action-packed video I made for this doodad.
As with “traditional” fuzz-face units, turning the output knob down reduces high-end response, since the pot was 500 kOhms and moving the wiper would introduce enough series resistance into the audio path quickly enough to roll off high frequencies. I used a linear pot (marked B500k) instead of an audio-taper pot (A500k) because I like that better.
Okay, there are two great big Mallory polyester-film capacitors on the circuit board, and one silver-mica cap (the semi-visible black thing between the two transistors). Why did I use them instead of smaller, cheaper ones? Because… I could. And because I had a bag full of each of them from back when I used to build whole guitar amps. And because… they’re cool. Seriously. They are.
The transistors I used are 1) a BC109 for Q1 like the schematic says, and 2) a BC109C for Q2 instead of a BC108, because I couldn’t find any BC108s anywhere. Both transistors are Silicon, not Germanium, so they don’t need to be individually tested and biased, unless you’re really bored or something. I left room on the PCB for sockets, so I could try different transistors. This unit uses NPN transistors, not PNP.
The enclosure is a 125B, which is similar to the Hammond 1590N1.
If anyone is wondering, I ran a bass through this (Fender P) and it sounded like dogs***.
One more thing: the two holes near the white Mallory capacitor are for standoffs. They are sort-of visible in the interior shots. I used plastic ones that are a little too small for the holes, so I glued them to the underside of the board. With the modern miracle of Elmer’s glue.
If anyone wants to make one of these, here are the layout diagram and an image for etching if you want to burn the PCB yourself:
BOM (Bill of Materials) for this project:
OSHPark PCB for this project:
https://oshpark.com/shared_projects/8z6KHQba
-T. Hallenbeck
th@thallenbeck.com