Boss HM-2 New Mods!

Happy new year everyone! 

Here's a Boss Hm-2 "Guitar Dreamer" modification! Can the death-metal-oriented HM-2 sound like a tube-screamer or other overdrive pedals? The answer is Yes! 

Here's the schematic diagram of the stock Hm-2:

http://www.hobby-hour.com/electronics/s/schematics/boss-hm2-heavy-metal-schematic.png

Here are the steps to modify the Hm-2 and turn it into a way more usable Od /dist pedal:

1)First of all, If you own an older "ACA" type Boss pedal designed for power supplies up to 12Volts DC, simply replace D1 and R2 with two jumpers and use a regular 9Vdc regulated power supply. If you own and old ACA type psu and the Led indicator of the pedal lights up bright, just skip this 1st step.

2)Replace the C11 capacitor with a 1nF to 10nF one. Less capacitance equals more trebly, british-like response and less "muddy" tone. If you like fat tones, skip this step.

3)Remove the D6 and D7 Germanium-type diodes and place jumpers in their place. This will remove the "nasty" fuzzy crossover distortion character of the hm-2 and turn it into a normal distortion pedal. 

4)Remove the D3,D4,D5 "overdrive" diodes completely to get a different distortion "DS-2"-like character. Keep them in place while removing D8,D9 for more overdrive-like tones. I chose to keep the D8,D9 and removed the D3,D4,D5 for this mod. You could also replace these diodes with LEDs. The red leds are closer to the diode distortion character while green leds sound softer. You can mix the colors of the LEDs (eg. D8 = red Led, D9 = green Led) for assymetrical clipping which sounds more tube-like.

5)Replace C16 with a 10nF, 22nF or 47nF capacitor. This will remove many of the nasty fuzzy highs and make it sound amp-like (it's sort of like a cab sim). Higher capacitance = less treble and fuzz.

6)Replace R53 with a jumper for extra output level. This mod will increase the output level so you can dial in "booster" like tones with less gain and more output.

Cheers,
GuitarDreamer
Jan 2017