Fred Briggs - Hummingbird Overdrive

I've been working on this pedal for around two months now. From conception to completion it is the longest I've ever spent on a stompbox project. I think it's paid off. Prepare yourself for some "mojo" chatter, here it goes -

The original idea was to create something a little like the BJF Honeybee Overdrive - a slew rate limited overdrive pedal which produces lovely soft overdrive tones (Slew rate is the rate at which a device can react to changes in a signal's amplitude - if you limit the slew rate the audible effect is a softening of the higher frequencies). Unlike the Honeybee though I wanted to keep the highend of my signal intact, unlike the roll off produced when you "dig in" to the Honeybee (created by what I believe is a feedback capacitor from diodes that clip to ground to the - input of an op amp chip, confirmation will be coming VERY shortly :-).

I started out looking at how slew rate limiting was achieved. Mostly it involved the use of an op amp chip such as the LM301 or CA3130 (Keep this chip in your head - I'm sure we'll be seeing more of it in the very near future! ;-) and an external compensation capacitor. I didn't want to use a chip in my design so I decided to go discrete! I started by taking the discrete op amp circuit from the boss blues driver circuit, well know for it's dynamic response to playing styles. This was my starting block. From there I made significant circuit modifications, firstly to induce considerable slewrate limiting and secondly to create a soft, dynamic overdrive that can be stacked very nicely with other gain pedals. After I had my basic sound I then fine tuned each individual section of the build, hand selected parts and tuned values to their optimum tonal values. I settled on a mixture of Metal Film and Carbon Composition resistors with a combination of Paper in Oil, Silver Mica, Metal Film and Tantalum capacitors. 

This rampant, unaffected parts selection ended up with a bill that was not too cheap but definitely worth it; this is, without a doubt, my favorite overdrive pedal. It is as dynamic as the Fulltone OCD while being much softer and playable at higher volumes. The high end is tamed and efficient, it'll still be there even with the gain maxed and volume low and it's always soft and syrupy with a chewy texture that allows notes to melt out from the fretboard. The "Nectar" control I incorporated allows a steady increase in low-end response meaning that you can lower the bass content for bass heavy amps while paying through humbuckers or twin the Hummingbird with brighter, single coil equipped guitars such as the telecaster without any compromise in playability.

I'm so happy with this design that I'm building myself another - the Hummingbird De-Luxe with two extra controls for "Sag" (Which you can see on the gut shot as a small black trim pot) and "Shimmer" (A treble boost/cut control). Check out the shots below!