Boss - HM-2 Heavy Metal

Crumbchildz · Post by **Crumbchildz** » 19 Apr 2011, 13:27

That is fuckin SIIIIICK! Where'd you catch Rotten Sound?

RnFR · Post by **RnFR** » 19 Apr 2011, 19:30

killer shirt!

Pruttelherrie · Post by **Pruttelherrie** » 21 Apr 2011, 07:36

Crumbchildz wrote:That is fuckin SIIIIICK! Where'd you catch Rotten Sound?

They are wrapping up the European tour, some 4 or 5 gigs still to go. Saw them on the only dutch show, on the other side of the country (still only a two hours drive

Crumbchildz · Post by **Crumbchildz** » 21 Apr 2011, 14:47

LUCKYYYY! I don't think they'll be coming to the US anytime soon. The last 2 or 3 tours they had scheduled go canned at the last minute. VISA DENIED!

Pruttelherrie · Post by **Pruttelherrie** » 14 May 2011, 11:41

Soooooo... I played a bit with the HM-2 to get 'that' sound. It works perfectly, all at max into a dirty channel.
Next I built a splitter/blender, to mix that mid hump into my normal sound. With the blend pot you can finetune how much of 'that' sound you want into your own sound. But if you use it that way, you get the lower gain of the HM-2 directly into the poweramp, if you don't feed it into a dirty channel (the splitter/blender makes it parallel to my high-gain sound).

So I was thinking about making a filterpedal, with only the filtersection of the HM-2, and put that in the loop of the amp.

I came up with this: (component numbering same as the nico schematic above)

This is only the filtering section with an input buffer in front of it. Could somebody please do a sanitycheck on this? There's a mid pot in there for added control, but you can leave the pot out and bridge it to the high pot for the classic version.

And this is the board I made, could probably be a bit smaller but I tried to keep the traces kinda wider for easier etching. At 1.7"x1.45" it should fit in a 1590B I think.
http://dl.dropbox.com/u/17081629/swedis ... /board.png

The component placement:

For those interested, Eagle project files:
http://dl.dropbox.com/u/17081629/swedis ... ainsaw.sch
http://dl.dropbox.com/u/17081629/swedis ... ainsaw.brd

I'm planning to build this somewhere next week, don't feel like breadboarding and don't have a printer at home...

Pruttelherrie · Post by **Pruttelherrie** » 14 May 2011, 11:45

Oh, forgot to ask, '10k G' means linear, right?

Crumbchildz · Post by **Crumbchildz** » 14 May 2011, 17:30

Unfortunately, no. The "G" is roughly the same as "W" as far as the taper is concerned. I've had no luck at all finding 10k-G pots, but 20k-W works fine. You may have to adjust the 3k3 resistors (R52 & R54). Good Luck!

Pruttelherrie · Post by **Pruttelherrie** » 14 May 2011, 21:05

Aha ok, thanks. But it just occurred to me that the whole point of this thing is to have them maxed anyway

I could get away with no pots at all!

Playing with the HM-2 a bit more, most of the magic happens in the last 10% of the high-pot's range. I could use a 1k lin pot with an added 10k resistor so that the upper 10% of the range expands to the whole turning range for finetuning.

Will report later.

Cableaddict · Post by **Cableaddict** » 13 Oct 2011, 18:17

Hey, folks.

I just found this amazing website after finding my old HN-2 in a dusty corner of my studio. I forgot how much I used to love it. (Yes, I like it stock. It only does one thing, but it does it well.)

So my question isn't re the circuit, but the power supply:

Many OD pedals sound MUCH better with 12v or even 18v. Some fuzzes sound subjectively better with less voltage (old carbon batteries, whatever.) Earlier in this thread, Member "Fuzzed" said he likes his with about 6v.

I'm dying to experiment, but the psu jack takes an AC adapter, not DC. I assume the pedal converts to dc internally, so how exactly would you vary the rails on this thing?

Cableaddict · Post by **Cableaddict** » 13 Oct 2011, 18:23

Maybe just wire the internal battery wires to a jack, and use a DC psu?

- Makes me wonder why some pedals use an ac adapter at all. That's quite OT, but a good question, if someone has a simple answer.

ddpawel · Post by **ddpawel** » 13 Oct 2011, 19:04

Crumbchildz wrote:Unfortunately, no. The "G" is roughly the same as "W" as far as the taper is concerned. I've had no luck at all finding 10k-G pots, but 20k-W works fine. You may have to adjust the 3k3 resistors (R52 & R54). Good Luck!

"Unfortunately" "G" is almost the same as "A" [1].

Bibliography:
1. http://www.keikocorp.co.jp/components/p ... tails.html

Pruttelherrie · Post by **Pruttelherrie** » 15 Oct 2011, 09:30

Pruttelherrie wrote:Aha ok, thanks. But it just occurred to me that the whole point of this thing is to have them maxed anyway
I could get away with no pots at all!

Playing with the HM-2 a bit more, most of the magic happens in the last 10% of the high-pot's range. I could use a 1k lin pot with an added 10k resistor so that the upper 10% of the range expands to the whole turning range for finetuning.

Will report later.

Hmkay, so here we are, a couple of months later, reporting.

Over the summer I did a few things with this filtering:

1) I built the 'pedal' described above, just the filter in a 1590B. Input, output, power. No knobs but I plan to put the 'maxed out' picture on top.
It works like a charm! Put in the loop of my Powerball I can tune the amount of character with the wet/dry control. This way I can slowly get the rest of the band to accept this change. Boiling frog and all that.

2) I changed a few values in a Boss GE-7 pedal so that the interesting bands are exactly at the HM-2 frequencies. I was in there anyway to change the opamps and caps so this was an easy fix. This works as well. This has the added advantage of being able to tune the sound a bit more, but I mostly leave it set at the maximum boost of the three bands.

3) I had a MT-2 lying around. Bought secondhand for backup purposes but I never liked the high-frequency fizz that was always present. So I changed the two existing fixed post-distortion gyrators (built around Q007 and Q008 in the factory scheme floating around) and added a third one in spiderweb technology. For completeness I added a trimpot to dial in the amount of filtering, but I mostly leave it at max. This trim pot is accessible through a small hole in the side of the pedal.
It works and makes the pedal much more usable! Also you still have the normal tone controls for fine-tuning, although the parametric mid is *really* sensitive.

So next up is a Powerball lead stage in pedal form, followed by this filter. I really like the fullness of the Powerball sound, this filter just is a *thick* layer of icing on the cake!

Also up is a bit more testing with an old Alesis QuadraVerb, to see if I can mimic this sound in a rack effect.

Pruttelherrie · Post by **Pruttelherrie** » 15 Oct 2011, 09:32

Pruttelherrie wrote:reporting

I'll see if I can make some sound clips too! Unfortunately I sent the MT-2 (HMT-2

) to a friend so I'll have to wait till I get that one back before I can make a clip of that...

nitraus · Post by **nitraus** » 09 Jan 2012, 19:57

A useful mod I did on my HM-2 to use it with bass is to put a fixed resistor (bypassing the 10k high pot) to trim the high frequencies in order to use the high pot to control mids. It was too fizzy, and controlling the mids I can control the bass presence in the mix.

Since I dig this mod a lot, could anyone tell me which values should I experiment in order to change the frequencies of mids and highs? It would be really useful in order to make a semi parametric eq (a bit like the one on MT2) with better frequency control.

greigoroth · Post by **greigoroth** » 10 Jan 2012, 20:08

I think the comments in this thread show how many different cool sounds you can get out of the HM-2. Fine, the controls are odd, but it's pretty far from a one trick pony. Sweet Rotten Sound t-shirt by the way! Hoping a Swedish date gets added to the Grind Over Europe tour.
Going to have to pick up a Behringer and A/B it with the HM-2.

JiM · Post by **JiM** » 11 Jan 2012, 23:28

greigoroth wrote:Going to have to pick up a Behringer and A/B it with the HM-2.

Which one is it ? i guess it's the HM300, but there are several other metal distortions in there ...

greigoroth · Post by **greigoroth** » 12 Jan 2012, 07:40

JiM wrote:
greigoroth wrote:Going to have to pick up a Behringer and A/B it with the HM-2.
Which one is it ? i guess it's the HM300, but there are several other metal distortions in there ...

Yep, that's the one. Although I think it may be more internet rumour than anyone looking at the circuit.

RnFR · Post by **RnFR** » 13 Jan 2012, 02:22

Pruttelherrie wrote:
2) I changed a few values in a Boss GE-7 pedal so that the interesting bands are exactly at the HM-2 frequencies. I was in there anyway to change the opamps and caps so this was an easy fix. This works as well. This has the added advantage of being able to tune the sound a bit more, but I mostly leave it set at the maximum boost of the three bands.

i'd love to see your mods for this. i've got one of these lying around i never use, and this sounds like a fun little "secret weapon".

are the circuits similar, or are you just shooting for the same bands? i honestly havent taken the time to compare them. i'll do some reading, it's an easy tweak i'm sure. the extra high band could possibly be set even higher as a kind of poor man's noise reducer when you reduce the gain.

MoonWatcher · Post by **MoonWatcher** » 13 Jan 2012, 04:59

RnFR wrote:
Pruttelherrie wrote:
2) I changed a few values in a Boss GE-7 pedal so that the interesting bands are exactly at the HM-2 frequencies. I was in there anyway to change the opamps and caps so this was an easy fix. This works as well. This has the added advantage of being able to tune the sound a bit more, but I mostly leave it set at the maximum boost of the three bands.

i'd love to see your mods for this. i've got one of these lying around i never use, and this sounds like a fun little "secret weapon".

I've got some cheapo Rogue or similar plastic knock-off of the Boss EQ that I never use, either. I had ideas of tweaking 3 bands to mimic the HM-2, but wouldn't have felt like I did a complete job w/o tweaking the other 4 bands. But since the HM-2 doesn't try to cover a 1/2 octave, 1/3 octave, etc. - I have no idea what bands to shoot for. I honestly don't know how Boss came up with the 3 that they did.

I had my EQ apart once, and it doesn't look like it would be fun to tweak. All of the op amps are the SIP-8 types (I'm assuming the GE-7 is the same) with caps and 1/8 watt resistors crammed in between them. The electros are really on the small side. I repaired a failing DD-2 about a year ago and went with 1uF & 10uF tantalums just to keep from going nuts dealing with the congested PCB.

I wonder if it's a case where using the 3mm lead spacing Wimas (or similar) might make things easier, or multilayer ceramics for any caps 100nF or smaller.

Pruttelherrie · Post by **Pruttelherrie** » 13 Jan 2012, 12:02

RnFR wrote:
Pruttelherrie wrote:
2) I changed a few values in a Boss GE-7 pedal so that the interesting bands are exactly at the HM-2 frequencies. I was in there anyway to change the opamps and caps so this was an easy fix. This works as well. This has the added advantage of being able to tune the sound a bit more, but I mostly leave it set at the maximum boost of the three bands.

i'd love to see your mods for this. i've got one of these lying around i never use, and this sounds like a fun little "secret weapon". are the circuits similar, or are you just shooting for the same bands? i honestly havent taken the time to compare them. i'll do some reading, it's an easy tweak i'm sure. the extra high band could possibly be set even higher as a kind of poor man's noise reducer when you reduce the gain.

They are really similar, see below.
I only cut out the relevant parts of the schematics (copyrights, fair use, yadda yadda, but also because the rest would just distract from the analysis)

First the gyrators of the HM-2:

The GE-7 gyrators:

I changed the values of the 100Hz, 800Hz and 1.6kHz gyrators, like so:
C13: 0.056 -> 0.068
C6: 0.0082 -> 0.0068
R7: 100k -> 82k
C15: 0.0039 -> 0.0047
R21: 82k -> 100k

So replace 3 caps and move R7 and R21 around... And as I said, once you're in there it might be smart to upgrade the opamps and caps to higher quality ones! Although it's not really necessary if you use it to shape an already noise-like distorted sound

The only thing with this mod is that you cannot get a flat band anymore with all the controls in middle position since they're not exactly overlapping anymore. but if you want a flat band just turn the thing off!

On an unrelated note: where can I get these small sliderpots, or those centered-double-pots like in the MT-2?

Boss - HM-2 Heavy Metal [schematic]