Boss HM-2 re-housing and modification. ‘Makeover’ might be a better term for this. It’s what inspired the ridiculously long analysis post about this circuit. This job was a delightful empty canvas to do whatever I wanted, courtesy of recent Converse-Rubber-Tracks-alums Expander from Austin TX.



Modifications are based on my own HM-2. I always make sure to retain access to the stock sound whenever I do work on these pedals.

I upgraded all the caps to >25V so that the pedal can run at 18V. Higher supply voltage yields a really different sound, since the EQ stage is often clipping at extreme settings, particularly with the switchable clipping mods here – running at 18V keeps the EQ much cleaner and emphasizes the more filtered sound of the earlier stages. Couplers in the signal path I replaced with film, especially tantalums.



With the three toggles down, you get the stock sound. One is an LED option for the first distortion stage, one is an LED option for the third distortion stage, and one is a lowpass filter @ 7kHz in case things get too hairy/fizzy. Using the LED for the first stage yields much more asymmetry and amplitude there, which changes the duty cycle of the later clipping stages and sounds more ‘saturated.’ Using the LED in the third stage increases headroom and output markedly, since the final stage’s clipping threshold goes from 1Vpp to 2.7Vpp and allows for truly boosting an amp with the HM-2′s weird EQ curve. It also overdrives the EQ stage to hell when it’s cranked, which is its own unique tone (though this can be mitigated by running at 18V). The lowpass can take some of the buzz off and emphasize the lower harmonics when running into a truly clean amp. Not the kind of thing you want on all the time, but useful in certain situations, like chilling out the fuzzy opamp overdrive of the EQ stage.



Knobs are the same as the stock pedal. I did keep the option for battery power in this case, since I was allowed to use a pretty roomy enclosure.

