Rochambeau

A Fun Little Dirty Boost That's a Real Kick in the Pants!

Ok, ok, ok. I know, this is now my second dirt box when I say that my projects aren't that. Well, this one was a fun little experiment that I decided to keep. Not only that, it is inspired by a pedal with probably the best name ever. Ram the Manparts is a discontinued dirt box that gets some great fuzzy, something-y tones. I decided I had to mess around with the circuit. The schematic is not freely available, but I reversed it from one of the layouts around out there. Instead of a straight up dirt box, it is more of a dirty boost, with huge amounts of volume on tap. With the volume low, it gets solidly into mid-gain territory, but it's not going to be over the top gainy on its own.

First, I decided I didn't like the sag control. It's just too spluttery and not much usable range for me. Additionally, the gain switch wasn't my jam, so I got rid of that as well. Now let's look at the Rochambeau schematic.

Rochambeau Schematic

I noted that it has a wide range of gain levels with the guitar volume rolled off, but being a neanderthal who doesn't roll off the volume while playing, I put in a "dirt" control that is really an input volume control. Pretty simple, right?

Next up I wanted some tonal control, as it can get some harsh harmonics with certain pickups and gain settings. So Mark Hammer's Stupidly Wonderful Tone Control to the rescue! It's two resistors, a cap and a pot and values were chosen to all be usable. I hate tone controls that are too drastic; no one wants zero treble, they just want to tame it. If you want zero treble, that's what the guitar controls are for :).

Next up, I felt like we could do something exciting by essentially taking this pedal and giving it some hard clipping. Because the output of the LM386 can be so hot, I decided to use red LED's. I tried green, even, but they were a little too raggedy sounding. However, I wanted to be able to dial in the amount of hard clipping, so the "extra" control is a variable resistor from the LED's to ground. Fully rolled off and the resistance to ground is such that the LED's aren't really doing anything. Fully up and you get full LED clipping, with varying shades in between. A nice little "extra" option that provides some interesting sounds and textures.

Nothing too crazy there! Just a fun little box. I whipped up a PCB layout to fit it into a 1590A, albeit a tiny bit snug, but careful drilling should make it work just fine. Also, 9mm pots, man. No way you're sticking those big ol' 16mm pots in that tiny enclosure. There's just too many!

So if you're a bit of a dirt box junkie like I am, go make one! Build docs, layout, etc. are here.