BOSS HM-3 (not HM-2 !!!) the most hated/underrated pedal

Discussion in 'Reviews' started by Tetanus, May 20, 2018.

  1. Tetanus

    Tetanus Well-Known Member

    Jul 17, 2012
    UK, Bristol
    ok guys. I am a huge fan of Fortin pedals (and amps). As you might know i own a Randall RD amp which is been designed by Mike Fortin, a Fortin Zuul noise gate, and a Fortin Grind booster. I used to own a 33 Meshuggah signature Fortin booster as well, but i sold it for double the price i purchased it which founded me the zuul and grind together... :)
    The Zuul is the best noise gate on the market. Period.
    The 33 and Grind pedals are extremely good booster pedals to tighten up your sound. BUT(!) since i got an old Boss HM-3 (Hyper metal, not the hm-2 Heavy metal!!!) pedal, i have to say it can get really close to these boosters. The active bass and high tone controls on the HM-3 can provide the same tightness as the Fortin pedals, plus it is adjustable, not fixed like on the fortin ones...
    Although there is tons of bass in this pedal.
    the level at max might not give you the same amount of boost, but it is really close, and it is just enough to use on the OD channel of an already gainy amp as a booster.
    The dist could be at zero, but even then adds a bit of that fuzz and grit, which reminds me to the famous Swedish tone (HM-2), but it is not as fuzzy; more articulate, cut through the mix etc.

    It is between the hm-2 heavy metal and mt-2 metal zone.
    This pedal is awesome as a booster on the dist/od channel of a gainy amp.
    On its own it sounds shit....

    P.S.: I still love my HM-2 pedal as well, but the HM-2 is way to fuzzy, messy etc. This HM-3 is more modern and fits more into the band mix.

    I am already looking the schematics to try a few mods. For example:
    -add an amp channel switching output like on the Fortin grind/33 pedals;
    -add more volume boost option;
    -add a switch which eliminates the distortion/clipping diodes entirely (convertng it to a booster)
    -add additional tweaking option as this pedal got tons of Bass on touch.
    Last edited: May 21, 2018
  2. Tetanus

    Tetanus Well-Known Member

    Jul 17, 2012
    UK, Bristol
    ohhh my.. I spent quite a few hours to check the schematic of the HM-3. I had so many ideas... Finally i started to do some experiments.
    I started to replace a few resistor and/or capacitors in the high/low-pass filters between the gain stages. Actually the stock versions were working great so went back to stock.
    I tried a few different diodes in both clipping sections. At the end i ended up with 2 switches, 1 is eliminating the diodes, the other is replacing the hard-clipping diodes (D5 and D6) with red, 5mm LEDs.
    sw1. no diodes:
    great boost pedal with "Dist" on minimum, especially as the High and Low controls on this pedal are active, which means they either boost or cut their frequencies.
    but turning the "Dist" control up will push the pedla into an "op-amp fuzz" pedal. I love both of these sounds.
    sw2. stock diodes vs LEDs:

    the stock silicone diodes are actually sound great. I tried the usual 1n419/1n4148 diodes and they didn't sound better... so left the stock diodes in. The Germanium Bat42 (i think) was not my cup of tea either.
    the silicone diodes in this pedal gives that "chainsaw" like character, which i love. The LEDs sound less compressed, more open, more warm. Combine this type of clipping with the op-amps' overdrive sound and you can either have a nice overdrive sound or a crushing fuzz like tone.

    I added a "tightness" switch at the end of the signal. this works great as fixed switch, but i will experiment to make it adjustable.
    I also would like to install dual-concentric pots and open up the tone controls. The "High" control actually controls the mid frequencies as well, and i will try to use separate controls for these two. I also would like to add a freq. control for the mids and for the bass as well. (this pedal got tons of bass and gets really boomy really easily).

    So here is what i have in mind to end up with:
    4 concentric pots for:
    - Volume and Dist.
    - Low and it's Freq.
    - Mid and it's Freq.
    - High and (instead of it's Freq. control add) a variable Tightness control (instead of a fixed switch)

    two switches:
    sw1: Boost / Distortion mod. (basically disable or enable diode clipping )
    sw2: choose between 2 type of diodes. (Stock / LEDs)

    I also was thinking to install a DIP8 IC socket adapter and try different op-amps. Mainly the burr brown OPA2134...

    to be continued...
    Last edited: May 28, 2018
    Robstafarian likes this.

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