Michael Klein Audio Design Corpse Flower Discrete Boost

Corpse Flower is a discrete boost that is inspired by the Rangemaster treble booster but offers a wider range of tones and flexibility. My love for this design started with my love of the riff, and Lord of the Riff – Tony Iommi. I think this circuit works well in several applications, but certainly likes to make things heavy.

My take is quite unique and features a control the likes of which I’ve not seen on a pedal before – BLOOM (more below) – although has probably been done somewhere. I’ve decided to use a combination of modern WIMA poly capacitors, low-noise metal film 1% resistors, and NOS Telefunken transistors that I test and sort...which is too a bit atypical for this type of design.

Controls

BLOOM - BLOOM is a true “hfe” control. In other words, this control varies the actual gain of the transistor. Traditional transistor-oriented gain controls work as a voltage divider, a variable bypass capacitor, or sometimes even a bias adjustment. BLOOM is none of those and allows the user to cover the gamut in what accounts for much of the variability from Rangemaster to Rangemaster = individual transistor gain.

Some transistors are higher gain, and not only output more volume (in this case) ...but also respond more compressed and have a slight slur on pick attack. Low gain transistors have more headroom, better touch sensitivity, but are also a bit less harmonically complex. BLOOM allows you to pick anywhere between those extremes.

At minimum, the transistor operates under quite low hfe characteristics, and as BLOOM is increased the transistor gain increases correspondingly. I personally like this between 12:00 and max for all my guitars.

NOTE – because of how this control is designed, you will notice a bit of transistor “groan” as you turn this control. This is totally normal and well worth it’s benefit, in my opinion.

STENCH - STENCH adjusts the low-frequency content of Corpse Flower. At minimum settings, I’ve set this to mimic the frequency response of a stock Rangemaster. This is a high-pass filter right around 500Hz. As STENCH is increased, this frequency knee is lowered, all the way to an extremely thick, doom-like tone.

Lower settings work well to tighten up the sound of a guitar or to add percussion. Higher settings work well to maximally overdrive your amplifier and create a large wall of thick sustain. You will likely find that STENCH will help dictate this pedal’s use in the style of music you play!

DEATH - DEATH controls the output volume of the Corpse Flower. As an homage to the original, I kept this control similar in design and behavior to the Rangemaster. Most of the boost range is in the latter half of its travel and is obviously interactive with BLOOM.

For a very simple design and control layout, I hope you’ll find a wide variety of tones and uses in this little box!