What can be said about the Tonebender that has not already been said a million times over? I originally got interested in this circuit for bass during some extensive research into the effects of Tool’s Justin Chancellor, who had been known to use a Coloursound Tonebender mkIII placed at the end of his signal chain. Naturally, I wanted to try some of those crunchy bass fuzz tones for myself, but since I started building pedals a couple years ago, I’ve had a bit of a mixed relationship with the Tonebender. My first attempt at building one was with silicon NPN transistors, as I was still relatively a noob and hadn’t yet tried my hand at builds featuring germanium transistors. I tried quite a few times with the silicon, but honestly I just didn’t like it at all. I didn’t experience that instant “a-ha” moment like I did with, say, a decent Russian Big Muff.
That changed about a year later once my good friend and pedal guru Anton gave me a handful of germanium PNP transistors. Suddenly, the key to the beastly Tonebender tone was in my hands. I breadboarded the circuit (which was pretty simple), and was really impressed at the difference that the germanium transistors made. The gain stages and output volume were perfect for what I needed on bass. What I didn’t love about it was the tone control —despite it being an equivalent to a Big Muff tone stack, I found it incredibly counterintuitive that the stock circuit increases the bass response by turning the control clockwise, and that counterclockwise increases the treble.
After a little bit more digging on the internet, I found a schematic with some excellent mods by Tone Burner. What TB did was essentially replace the Tonebender’s BMP tone stack with a Baxandall tone stack which in my opinion is perfect for bassists—I particularly love the high end it can deliver while still letting your bass push a big, phat, woofing fuzz on the low end.
TB also added another potentiometer (control name “String”) that allows you to bias the third transistor in the circuit. I found this control to be subtle, but ultimately shines for us big, dumb bassists who like to use big, dumb picks on their big, dumb basses. It does somewhat compress the attacks on the string, allowing the attacks to come through a bit more when the control is turned clockwise. Maybe this is why it’s called “String”—in any case, on my version I called it “Attack” which seemed a bit more intuitive.
As a final note, I did modify the circuit only slightly by switching out the input cap to allow more bass response at the circuit’s input. The result became a surprisingly rich and versatile effect, one of my absolute favorite bass fuzz pedals to date, and has been sitting on my board since its creation, and the name—a reference to one of the best films ever made—still gives me a good chuckle.
I designed the layout a little bit before I made a conscious decision to swear-off off-board wiring. It’s not so bad on this one, but most of the other layouts I made after this one attempt to solder the pots directly onto the perf-board. You may also be wondering what the squares are on the side – they are simply the holes at the side of the extra piece of perfboard for which I designed the layout.
Don’t forget to wire the power connection appropriately for center-positive power. This is a Tonebender, after all.
Here is my finished version of the prototype pedal, inside and out: