The Kowloon Walled Bunny

Well over ten years ago, my band played a show with Pound, WI. Russell Hall, the guitarist (who now plays in the spectacular United Sons of Toil), was using a Ross Distortion. I thought it sounded great. Sometime around 2001 or 2002 I picked one up at a secondhand guitar shop. I really loved it. I still own it and I still love it.

Sometime soon thereafter, when I began to research pedals for fun, I discovered that the MXR Distortion +, the Ross Distortion, and the DOD Overdrive 250 were all essentially the same circuit with only slight differences. After looking at the schematic, I had a lot of ideas for possible mods, but I never got around to trying them.

Let’s jump to 2007. My friend Scott Evans of Kowloon Walled City had a number MXR distortions. He had one that he really liked, and sounded different than all the rest. We had a little shootout.
Scott's Pedals

What we discovered is that the one that Scott really liked had a broken clipping diode. Essentially, it was as if a diode was removed. It sounded great, just rough edged, loud, and rude. I kind of wanted to do this to my Ross, but it was a nice old pedal, so I refrained.

This year Kowloon Walled City released their second album, which is astoundingly good and can be downloaded for free! I figured I would force them into an endorsement deal while simultaneously doing something I’d wanted to do for a long time; make my ultimate version of the Distortion + circuit. I pretty much just declared that I was making this pedal, and Scott and the other guys in the band were very excited.

So, what did I do? Not much, actually. I guess that’s a bad thing to say given that I want to sell these. I started building pedal with the belief that I wanted to be open and share information, so here goes.

Op amp:741. This is the classic MXR op amp. The Ross uses a 4558, but yeah, the 741 does sound better. People say it’s because it has a shitty slew rate and is just kind of crappy by technical standards. I’ve never measured, I just know I like the sound.

Resistors: I pretty much use the stock value from the Ross.

Caps: I almost use the stock values from the MXR. There is no 10pf in the negative feedback loop of the op amp, since it’s the 741. the one big Change is that I have raised the value of the input coupling cap from .01uf to .1uf. Since Kowloon Walled City tunes down to stupid, this will allow a bit more of fundamental to get through. The risk is that the distortion can get farty with too much low frequency input. I don’t care; I’m not looking for a tight metal distortion.

Clipping Diodes: I put in sockets so that the user can choose and change diodes whenever and customize their sound. The version I built for Scott has two Germanium 1N34s, which can be kind of quiet. However, I added a knob to the pedal called the GSE knob. That knob adds resistance between ground and one clipping diode, simulating Scotts broken pedal. Personally, I prefer one Ge diode and one LED. The pedal ships with a variety of diodes for user tweakability. It can also be run with no diodes and will act as a boost pedal.

So, here is the first production model.

Thanks for reading!

2 thoughts on “The Kowloon Walled Bunny

  1. Have you ever tried to use the other half of the chip for more output? It seems like it might not be bad, since it would also knock your signal back in phase, no?

    I’m building my first Ross/MRX/DOD jim-jam on a breadboard, and don’t really know shit from shinola, other than my the pedal becomes really trebly and then oscillates like crazy.

    • I’ve never tried that. Also, I’m using the 741 op amp, which just has one gain stage. It’s what MXR (and DOD for the 250) used before they went to the dual op amps, even though they only use half of the dual op amp.


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