Boss - HM-2 Heavy Metal  [schematic]

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Toasted
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Post by Toasted »

Hi guys, does anyone know any good mods for a stock Boss HM-2?

I'm especially looking to increase the bass response.

Cheers, Joe.

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Post by Bside2234 »

Try changing C30 to .022uf and C6 to 1uf.

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TubeDude22
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Post by TubeDude22 »

If you lift one leg of the .15uF tantalum capacitor that connects to the wiper of the "HIGH" tone pot, it will give you close to the tone you want. Boss wired the mid boost and treble boost circuit together to the High tone control for some weird reason. Increasing the high tone boosts both mids and highs. With the capacitor lifted, you can get more scoop in the EQ and more perceived bass.

IMHO,

TD

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Post by soulsonic »

TubeDude22 wrote:If you lift one leg of the .15uF tantalum capacitor that connects to the wiper of the "HIGH" tone pot, it will give you close to the tone you want. Boss wired the mid boost and treble boost circuit together to the High tone control for some weird reason. Increasing the high tone boosts both mids and highs. With the capacitor lifted, you can get more scoop in the EQ and more perceived bass.

IMHO,

TD
You could turn the Mid circuit into it's own control fairly easily. I did something similar by separating the Bass and Treble controls on a DOD American Metal to make it the same as an HM-2. It seems like no big deal to bump it up to the next step and put the Mid control in there.

It's hard to imagine anyone complaining that the HM-2 doesn't have enough bass... it has lots of bass available. With the stock controls, it's best to keep the Treble set low. A popular setting is to turn the controls so that they "face" each other - bass almost all the way up, treble almost all the way down... that's the classic Godflesh setting.
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Post by RnFR »

i'm a live sound engineer, and often the drunk idjuts i mix leave me presents at the end of the night. 8)
my latest is a Boss Heavy Metal pedal.
any tips on how to get this thing into screaming fuzz territory? it actually doesnt sound half bad, but it not all that inspiring either. i noticed that you can get them pretty cheap as well.
ideas?
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Post by RLBJR65 »

I don't know of any mods but the schematic is readily available. http://www.mif.pg.gda.pl/homepages/tom/files/hm-2.gif

Looks like it would sound like crap to me :lol: IMO soft clipping and hard clipping in the same pedal always sounds bad. I think I would try switching out the hard clippers.

What is the purpose of the GE diodes?

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Post by marshmellow »

Haha funny, same story with me. I brought a Boss TR-2 home yesterday. :lol:

But probably I'll find the owner again...

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Post by RnFR »

I think I would try switching out the hard clippers.
you talking about the silicon diodes?
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Post by RnFR »

in my anderton book it lists LEDs as soft clippers, so i'm guessing the germanium diodes are the hard clippers.

anyone want to field this for me?
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Post by Greg »

RnFR wrote:in my anderton book it lists LEDs as soft clippers, so i'm guessing the germanium diodes are the hard clippers.

anyone want to field this for me?
Soft Clippers = Diodes in the Feedback loop
Hard Clippers = Diodes to Ground.
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Post by STEPPEN »

Can the hard clippers be removed and completely bypassed without any major problems?

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Post by JiM »

You have 3 sets of diodes there :
- three in the feedback loop of the opamp, for asymetrical soft clipping (à la OD-1). To remove these, you'll have to desolder one leg in each brach.
- two germanium in series, which seems to be quite specific to the Boss "metal" pedals. To remove these, you'll have to shunt them (connect a wire across).
- two silicon to ground, typical hard clipper like a DS-1, a Rat, a MXR Dist+, etc. Again, to remove these, you'll have to desolder one leg of each.

An interresting mod would be to use switches to select which diode clippers are used in different combinaisons :
- no diode at all : i guess it won't sound good. Could be a clean, devastating gain booster with EQ, but i think the later opamp stages would clip by themselves quite soon.
- just in the feedback loop : expect an overdrive on steroids (not exactly a tub screamer)
- just the series Ge : i don't know, this could be cool ... or not
- just the hard clipper : it should sound a bit like a Boss non-metal distortion (DS-*)
- soft & hard, soft & series, series & hard : you'd tell us
- all of them : stock

Having all the combinations would be a tight fit in a Boss enclosure, no way for a rotary switch, maybe three mini switches ... i would simply use a DIP-switch. The remaining contacts would allow some other mods (add a cap in parallel of another to shift a frequency of the EQ, tame the input "buffer" (hey, in fact it looks like the first stage of a Big Muff ! You could mess with the 22 Ohm emitter resistor, from 390 Ohm to zero)

This pedal is (theoretically) really cool to mod, as it already has a bit of everything : you just have to remove a bit or another to change the sound !

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Post by pillowhead »

I've actually just finished modding and reboxing one of these that I had in my possession. I don't know if this will actually be of any use to the original poster, but my goal was to bring the gain back *down* to usable levels. One of the reveiws on Harmony Central said that the gain knob basically had three settings, off, on, and more on, and I think that's pretty accurate. As stock, I just don't think it sounded good, and certainly wasn't usable for my kind of music. Anyway:

Those two Ge diodes: it's my understanding that these act as a rudimentary noise gate, I removed these and replaced them with a jumper, with no noticeable difference.

From what I've played around with, if you want to make this pedal usable, play around with the frequency response of the gyrators in the final stage. I think that's where the most value is. AMZ has a good calculator for working out frequency and Q.

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Post by soulsonic »

Am I one of the only ones who likes the STOCK HM-2 sound? :cry:
C'mon guys - this sound is awesome: https://www.youtube.com/watch?v=76vGiZS6zFY
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Post by Emanuele »

soulsonic wrote:Am I one of the only ones who likes the STOCK HM-2 sound? :cry:
C'mon guys - this sound is awesome: https://www.youtube.com/watch?v=76vGiZS6zFY
+1
Not the best for "Heavy Metal" but it's the best rat alternative for 30$..

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Post by oscarv77 »

soulsonic wrote:Am I one of the only ones who likes the STOCK HM-2 sound? :cry:
C'mon guys - this sound is awesome: https://www.youtube.com/watch?v=76vGiZS6zFY
Nope, you're not alone... I have 2 of them. 1 in mint condition and the other as my daily-use dist pedal.

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Post by RnFR »

its not a bad sounding pedal, i just got it for free and was wondering if there was any way to kick it up a notch.
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Post by Bside2234 »

soulsonic wrote:Am I one of the only ones who likes the STOCK HM-2 sound? :cry:
C'mon guys - this sound is awesome: https://www.youtube.com/watch?v=76vGiZS6zFY
The HM-2 is one of the last stock pedals I own. I very much like the sound as it is a lot different than any of my other pedals.

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Post by Charon »

This is one of the most important distortion pedals on Earth, and one of the most desirable in all of heavy metal, specifically the style of catchy, melodic death metal that has been coming out of Stockholm Sweden for the last 20 years. Dismember, Grave, Hypocrisy, Unleashed, Evocation, and most famously, Entombed, (who actually haven't used the pedal for their guitar tone in years). The "Swedish Chainsaw" guitar tone is highly identifiable--you know it when you hear it. There is a distinctive mid-range buzz that under high-gain settings, sounds absolutely devastating. You need to know how to use the pedal, however, but it requires no mods or special tricks. Simply plug the pedal in as you normally would, turn ALL THE KNOBS ALL THE WAY UP, and go through your guitar amp's dirty channel (this is very important), with only a slight amount of gain (maybe 10%--you'll have to experiment), and also be sure that your guitar is tuned down, at least to C. (I tune to B standard). Power chords are massive, palm-muting destroys city blocks, and the tremelo-picked single note harmonic-minor melodies that are a hallmark of Swedish death metal, (think trem picked lines one might hear while listening to traditional Latin/Spanish guitar music), absolutely will saw the flesh off of every humanoid within a ten mile radius, burn your house down, and kill every bunny rabbit and kitten in your state, and rainbows may well not be seen in your area for generations.
Puppy dogs will be left unharmed. *Fido licks face, woofs
The sound is unique in that it actually accentuates a certain obscure mid-range frequency, in a genre of music where your guitar tone is usually "scooped" out, with very little mids. It is the antithesis to the typical American metal tone, which is very scooped, clean, and tight, and quite insipid in my opinion. American metal bands have really taken to copying Swedish melodic death metal, bands such as At The Gates, but they neglected adopting the signature guitar tone, opting for the bland, ubiquitous dual rectifier sound. The fools.

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Post by TubeDude22 »

If you look at the schematic in the link above, you will see the middle EQ circuit is tied to the treble control pot. As you raise (or lower) the treble you are dragging the midrange along with it. My favorite mod is to simply lift one leg of the .15uF tantalum capacitor, breaking the middle EQ circuit. I find the tone controls much more usable that way.

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