Boss - HM-2 Heavy Metal

lohstah · Post by **lohstah** » 04 Jan 2010, 17:15

i never played one, but a friend of mine who is a bass player had one and liked it pretty much as is.

moose23 · Post by **moose23** » 05 Jan 2010, 01:45

Yeah I've never felt any need to mod for bass, works great as is.

f2netxxx · Post by **f2netxxx** » 10 Jan 2010, 12:51

in first answer someone said to change C6 to 1uF to increase bass. isnt it too big change (0,047uF to 1uF)?

Fuzzed · Post by **Fuzzed** » 03 Jun 2010, 14:16

I noticed something funny about my hm-2!

When you feed it with just about 6v or 7,5v it gets into HARSH FUZZ OCTAVE TERRITORY.

It's freaking AWESOME.

maybe it's just mine that has a lot of years on its head, I really need to replace at least the caps, but hey try it! \m/

Steven_M · Post by **Steven_M** » 03 Jun 2010, 17:17

Fuzzed wrote:I noticed something funny about my hm-2!

When you feed it with just about 6v or 7,5v it gets into HARSH FUZZ OCTAVE TERRITORY.

It's freaking AWESOME.

maybe it's just mine that has a lot of years on its head, I really need to replace at least the caps, but hey try it! \m/

Yep! The HM-2 was my first pedal. I paid fifteen quid for it in 1996 and the person I bought it from told me it needed a new battery. Nope! No it didnt! this thing sounded awesome, until you put a fresh battery in at least!

MoonWatcher · Post by **MoonWatcher** » 03 Jun 2010, 20:13

lohstah wrote:i never played one, but a friend of mine who is a bass player had one and liked it pretty much as is.

Listening to old Godflesh tracks, I'm almost certain now that G.C. Green must have been using one as well as Justin. Sounds pretty damn good to me.

deadllama · Post by **deadllama** » 20 Oct 2010, 17:16

I just picked up an old DOD American Metal for $10 at the local Guitar Center. Before I crack this thing open, does anybody already have a handy schematic of the differences in the tone controls between this and the HM-2? Am I correct in believing the tone control ("Presence" instead of Bass and Treble) is the only real difference between these two puppies?

I don't play metal, at all, but for $10 I figured I could make this thing do some insane shit at some point or another.

borislavgajic · Post by **borislavgajic** » 21 Oct 2010, 06:33

GUTS

Boris

nitraus · Post by **nitraus** » 27 Oct 2010, 22:43

hey, just came across this thread and were wondering how i could control mids and highs separately. i'd like to keep highs at 12:00 (higher settings sound too harsh to me) and krank up the mids. any (simple) mod i could do? i'm totally a newbie

my idea was the following:

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.

so lifting the leg of the .15uF cap would keep mids at zero allowing control of highs, right? and i presume that lifting one leg of the .1uF cap would keep highs at zero allowing control of mids. is that true?
so i could keep the .15uF cap soldered and insert a 5k resistor after the .1uF cap bypassing 10k pot in order to have highs at 12:00 and allowing mid control.

what do you think about it? could it work?

MoonWatcher · Post by **MoonWatcher** » 22 Dec 2010, 04:48

I finally got around to tweaking mine just a bit. I mostly left the circuit stock - biggest changes were to replace D6 & D7 with BAT42 units for an even more pronounced noise gate effect, swap one of the hard clippers with a BAT41, and jumper a soft clipper, and replace one with a 1N4001. I also upped C29 to 220pF.

I replaced all of the electros in the signal path simply because I've experienced degraded performance with the higher gain Boss boxes with old ones. I don't have a particular affection for tantalums, but they won't degrade like electros will. There are a pair of 10uF units that I swapped for bipolar electros, though. The 1uF units are C3, C4, C12, C15, and C32. The 10uF units are C31 and C34.

Aside from those changes, I did add a mid pot. What I did was pull out the distortion pot and hardwire it for max distortion with a 220K resistor. I never intend to run this thing any way other than full out, so why bother with a control for it? My stupid reasoning, anyways. The other two pot lugs get shorted together.

I had a 20K pot from a DS-1, so I decided to use that for my mid control. I yanked out C28 and replaced it with a box cap rotated 90° and ran a wire from one lead down to the new pot's wiper. The other two lugs have wires that terminate where the bass and (now) treble controls connect.

The separate pot obviously makes a big difference, even though there is overlap between the two bands (958 Hz and 1279 Hz). The best thing about this flexibility is that it can be dialed in for particular amps - some would squeal like a pig prior to this. Now I can control it to a degree.

So it's still Swedish buzzsaw, but that is what I wanted to retain. It's also a little more flexible for dialing in that Slateman and Perfect Skin tone setup, as well.

remork · Post by **remork** » 27 Jan 2011, 23:15

bumpy bump

i've one open on the bench right now
but i've got a feeling that the only schem i could find for it isn't fully correct

and this link
http://nicosonic.free.fr/schems/BossHM2.pdf
seems to be dead?

any help highly appreciated!

RnFR · Post by **RnFR** » 28 Jan 2011, 01:36

here you go-

http://www.nicosonic.com/schems/BossHM2.pdf

i found it on his site. the address must have changed.

Pruttelherrie · Post by **Pruttelherrie** » 21 Feb 2011, 18:00

soulsonic wrote:SWEDISH CHAINSAW TONE FOR LIFE!!!!!!!

Hell yeah!

Now that we've got that out of the way, this got me thinking:

Charon wrote: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

MoonWatcher wrote:Standard tuning dropped to B with a combination of tube amp distortion and the right stompers always seemed to be the magical combination, but I never could nail the tones on those first two Entombed albums.

Would plugging this into a ROG Thor into a clean amp work as well, instead of plugging it into a JCM800-ish dirty channel?
I own an HM-2 as well as an HM-3, but haven't built a Thor (yet?).

Slabbefusk · Post by **Slabbefusk** » 07 Apr 2011, 09:54

Hey guys!

Can anyone verify that this schematic is a working one? http://www.mif.pg.gda.pl/homepages/tom/files/hm-2.gif

I'm in the process of making a PCB for it and it would be nice to skip building up on a labboard just too see if it works. I'm also going to build it with old metal can OP-amps just for the heck of it.

RnFR · Post by **RnFR** » 07 Apr 2011, 11:20

one page earlier in the thread is this factory schematic-
http://www.nicosonic.com/schems/BossHM2.pdf
I would just see if the two have corresponding values.

on another note, anyone know why they chose a pnp for the second inverting amp? does it have something to do with that gain control?

Slabbefusk · Post by **Slabbefusk** » 07 Apr 2011, 12:06

From what I see the smaller schematic has the switching circuitry omitted but the values of everything else is the same. I will build this with a 3PDT switch but as long as the signal path is the same it should work right?

I think the reason they chose a PNP is because the feedback voltage coming from IC1b will be negative in reference to ground. It's hard to say just from looking at the schematic.

RnFR · Post by **RnFR** » 07 Apr 2011, 12:21

yeah it should work fine.

I'm still trying to get my head around the pnp, but I'm taking a guess and saying it might have to do with getting the opamp to bias while being DC coupled to the PNP amp before it. my opamp Kung Fu is admittedly pretty weak, though. anyone else want to chime in here?

Slabbefusk · Post by **Slabbefusk** » 07 Apr 2011, 16:21

I don't think it has anything to do with the bias of the OP, that is supplied by the 4.5 V over R25 (68K) to the right of the PNP transistor. It could just be that the NPN and PNP transistors act as a complimentary pair. Why they do it I still don't know. I asked one of my professors about it today and he was leaning towards what I wrote in my previous post. He wasn't 100% sure either though.

Crumbchildz · Post by **Crumbchildz** » 07 Apr 2011, 18:00

I always thought it was a kinda "symmetrical asymmetrical" clipping. The NPN stage adds a bit of weird asymmetrical clipping to the positive phase of the signal, then the PNP stage adds the same asymmetrical clipping to the negative phase. Also, if you haven't already heard of them, check out Black Breath. One guitarist is using a HM-2 (dimed) into 2 Peavey VTM60's, other guitarist is using a HM-2 (dimed) into a Ampeg V4 and V2, bassist uses a HM-2 (lows dimed, highs at noon) into a blue line SVT. Monstrous sound.

Pruttelherrie · Post by **Pruttelherrie** » 17 Apr 2011, 10:08

Heheh I saw Rotten Sound on tour yesterday. They brought 4 support acts. Three of the bands (including Rotten Sound of course, see t-shirt below) used a HM-2 into a JCM-800 as their main sound

Of course I just *HAD* to buy this shirt!

Boss - HM-2 Heavy Metal [schematic]