Boss - HM-2 Heavy Metal  [schematic]

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Re: Boss - HM-2 ( Heavy Metal )

Postby mugician » 04 Feb 2009, 04:16

Ok. But if the diodes were in series, wouldn't I want to jumper both positions? I'll try what you said.

I removed the Silicon diodes to ground. The sound is even harsher and harder now :x .

So: remove Ge diodes that are in series, jumper only ONE of those positions. I'll report back in a minute.

PS - do you need a pic of the PCB or can you just look on the schematic?
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Re: Boss - HM-2 ( Heavy Metal )

Postby mugician » 04 Feb 2009, 04:30

No change in sound, just less distortion. Should I jumper both positions? Should I jumper the other diodes?
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Re: Boss - HM-2 ( Heavy Metal )

Postby Greg » 04 Feb 2009, 04:55

mugician wrote:No change in sound, just less distortion. Should I jumper both positions? Should I jumper the other diodes?


The diodes won't change the tone (to any major degree anyway), they're just there to clip the signal i.e. create distortion.
There's no reason removing the diodes to ground can make more distortion as the signal is clipped less, but.. it WILL be less compressed which yoiu might percieve as harsher.
The reason you only need to jumper 1 Germanium diode is that they're tied together at the ends anyway, as you'll see in the schematic... jumpering the 2nd one will make no difference.

You know, you're really groping around in the dark here. Maybe this isn't the pedal for you, or maybe you need to find some mod instructions that will get you where you want to go with it.
Wampler effects will have a mod for it and will describe the effect of every change.

I haven't played with one, and was simply trying to help by answering your questions about how to remove the diodes, but I don't know what you're trying to achieve....
Sorry :block:
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Re: Boss - HM-2 ( Heavy Metal )

Postby moltenmetalburn » 04 Feb 2009, 05:14

jumper those germanium diodes. try doubling up diodes on the hard clipping section or even tripling sometimes you can cut some gain that way. This is in my opinion a love or hate pedal, I still dont like mine after years and tons of mods. try another circuit in its chassis!
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Re: Boss - HM-2 ( Heavy Metal )

Postby mugician » 04 Feb 2009, 05:20

Wow. Oops. I've been going in a wrong direction for a long time. So hard clipping doens't sound different than soft asymmetrical? I was always under the impression that soft asymmetrical clipping would give me something like tube-screamer smoothness, and hard clipping would give me something like a RAT.

God. I'm totally lost now. More diodes means less clipping? I'm really turned around here. Someone have a link for an article explaining diodes in audio circuits so everyone doesn't have to explain?
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Re: Boss - HM-2 ( Heavy Metal )

Postby Greg » 04 Feb 2009, 06:09

mugician wrote:Wow. Oops. I've been going in a wrong direction for a long time. So hard clipping doens't sound different than soft asymmetrical? I was always under the impression that soft asymmetrical clipping would give me something like tube-screamer smoothness, and hard clipping would give me something like a RAT.

God. I'm totally lost now. More diodes means less clipping? I'm really turned around here. Someone have a link for an article explaining diodes in audio circuits so everyone doesn't have to explain?


Yes hard clipping sounds different to soft clipping.
Yes, more diodes means less clipping.

Try these and ask questions:

http://www.diystompboxes.com/pedals/diodes.html
http://www.muzique.com/compress.htm

Do a search on "diode clipping" or similar and have a read..
Enjoy.
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Re: Boss - HM-2 ( Heavy Metal )

Postby mugician » 04 Feb 2009, 07:43

Wow, thanks a LOT for that reading.

I guess what I'm trying to do here is make my HM-2 smoother, since I can't afford to get the parts to make myself a regular old TS. I had a TS9 RI a couple months back (sold it for rent, long story) and also a Boss CS-3 my friend gave me that he hated, said it was too noisy. I didn't like it either when I used it clean, but one day I accidentally kicked it on while the TS was on and I LOVED the sound. Absolutely fell in love with it.

I have this tone in my head ( :roll: don't we all...) where the OD I'm using has this smooth sound - smooth as in there aren't any violent or super apparent in-your-face freq peaks. I wanna hear something where none of the freq's jump out at you except maybe upper mids just a hair, and then I can do the rest with a comp.

I don't know. Once I get 50 bucks I'm gonna throw together a TS clone for myself, but until then I thought I'd try and see what I can do with what I have. The HM-2 I'm realizing isn't my thing.

It sounds excellent actually (especially with the new ICs in there, stock sounded terrible [maybe they were fried?]), and maybe someone here would like to take it off my hands. I got these super cool clearance knobs from Smallbear and an orange LED. I wish I liked the sound, because it's a cool looking pedal!
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Re: Boss - HM-2 ( Heavy Metal )

Postby soulsonic » 05 Feb 2009, 09:59

SWEDISH CHAINSAW TONE FOR LIFE!!!!!!!
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Re: Boss - HM-2 ( Heavy Metal )

Postby moltenmetalburn » 05 Feb 2009, 16:04

SWEDISH CHAINSAW TONE FOR LIFE!!!!!!!



hehe with that kind of enthusiasm I'm inclined to send you mine. It does a great job collecting dust. maybe you've got something you're trying to get rid of? I love Swedish metal but not this particular pedal. Just don't laugh when you open it up as it was the very first pedal I ever did any soldering in. I don't even remember what mods were done. PM me for details.
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Re: Boss - HM-2 ( Heavy Metal )

Postby soulsonic » 05 Feb 2009, 20:10

Today, I received the first of what will likely be several HM-2s...
Charon was absolutely right-on! All the knobs all the way up absolutely NAILS the old Entombed sound! The frequencies of the Hi control are exactly the perfect Swedish Chainsaw mid peak!!! I feel like a fool for not getting one of these years ago. I almost don't want to mod it now, it's so perfect. :lol: This is why I need to get several, so one can be left totally stock.
It looks like I can maybe fit a Mid control in the spot where the Check LED is...

I also absolutely agree with Charon about how much those Swedish bands have been ripped off in recent years. Swedish metal was one of my favorite things during my late high school and early college years of the mid-90's, and when I see all these American bands, I'm thinking "10 years too late, dude! Are you trying to be retro?" And they don't have the good sound either; exactly what he said, it's all Dual Rectifier/5150 crap... blah! These crazy on-the-edge guitar sounds are what sets that kind of music apart... whether it's the Chainsaw tone of Entombed or the crushing squall of Godflesh, the HM-2 has been a key ingredient to many underground metal bands, and it's a tradition that will live on and hopefully be re-discovered by new generations.
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Re: Boss - HM-2 ( Heavy Metal )

Postby moltenmetalburn » 05 Feb 2009, 20:54

Ha funny you got it today! You want another one? Pm me an addy and its yours...

The Swedish metal bands that started the popularity of this pedal are the reason I bought one, but Ive never like the sounds it gave me, and yes i did use it with all knobs at "11".

As for the new bands all using Recs and 5150's yes there are still guys using 5150s but many of the groups achieving commercial success with this "borrowed" sound/style are not, Not by a long shot.

The guys playing 5150s are the younger bands just starting out as Peavey gives em away like hotcakes! And try to get a rectifier for free, that just Isn't happening maybe for Hetfield... Ive seen more Kranks and Marshalls than anything else. The occasional "boutique" head Bogner, Diezel, Elmwood, Engl , Diamond etc..

Ive heard some great metal sounds out of many amps without the HM-2, different I'll agree but still great. C'mon there are other sounds that work just as well if not better, maybe not as recognizable... then again I am a non believer so maybe you are right.

Oh and just so it doesn't seem like I'm talking out of my ass the reason I "know" what amps are being used is that Ive Been on tour as a guitar tech for many of the popular new American metal groups playing late 90s thrash/death. Its what I do, besides trolling this forum and annoying all of you! :lol:

Oh and a little off topic but has anyone heard the 5150 III? On the last Darkest Hour run those dudes had just gotten them and I have to say they were awesome, really awesome. I will def pick one up one day.
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Re: Boss - HM-2 ( Heavy Metal )

Postby mugician » 05 Feb 2009, 23:49

So.

I was playing around with the pedal, and decided to remove all the clipping diodes. Except one. In the feedback loop of the op-amp. One diode left.

Here's my settings (into my amp's OD channel ONLY) level all the way up (insane volume, unity is at like 1, it's nuts), hi and lo all the way up, drive all the way down.

It slams the OD channel, and I just got done testing: I held a note (timed it) for an unnecessary amount of time. 5 minutes. I can sustain notes into boredom now. I've created something.

It's too much for me. I have no use for it. Someone take it from me! (And give me something to work on in return :wink: )
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Re: Boss - HM-2 ( Heavy Metal )

Postby juni » 10 Mar 2009, 12:07

TubeDude22 wrote: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.


I'm building a hm-2 clone, right now i'm in the process of redrawing the schematic. Though i'm studying electronics i am still a novice with these things, so i'm a asking you here..
Could a mid-eq control be added if i would disconnect the leg from the .15uF cap and wire another 100k potentiometer wired in the same manner as the high pot? Am i on the right track?

I'll skip the germanium diodes and i'll substitute the mitsubishi opamps with tl074's 4558's or the like. I also have an original hm-2 so i can compare how much it matters.

First post - thanks a lot for the forum! Hope i can contribute something to it in the future.
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Re: Boss - HM-2 ( Heavy Metal )

Postby strages » 29 Mar 2009, 11:42

Hey!

I would like to ask your help! I started building this effect pedal. But i dont know, what kind of the M5616L IC. What did you use instead? I think the NE5532 or the TL072.

Ps: Sorry for my english :scratch:
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Re: Boss - HM-2 ( Heavy Metal )

Postby juni » 31 Mar 2009, 12:55

strages wrote:Hey!
I would like to ask your help! I started building this effect pedal. But i dont know, what kind of the M5616L IC. What did you use instead? I think the NE5532 or the TL072.
Ps: Sorry for my english :scratch:


hi strages,

According to oscarv77 in this thread viewtopic.php?f=17&t=2066&p=24671:

"Any inline dual opamp will retrofit on there. I replaced all 3 with NJM5532L chips and got the one I had on the bench up and running."

"4558D
TL072
TL074
NJM5532L

I found that the NJM chip was considerably quieter than the other I tried. YMMV of course. Unfortunately, a socket would make the chip stick out too much, so experimenting is a bit difficult."


Haven't done mine yet, but hopefully it's going to happen soon. I have tl072's and 4558's to try at least.
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Re: Boss - HM-2 ( Heavy Metal )

Postby juni » 23 Apr 2009, 10:57

Ok, i've got some sounds out of my clone now.
Made some stupid mistakes on the board which i had to correct with messy wires but now it's almost there... So far i've only tried tl072's for the opamps, but i think they sound surprisingly good.
BUT there are some strange oscillations on extreme settings, not sure of the reason. Perhaps because of component placement, but there's also something strange about the EQ; the BASS pot works more like a strange gain control. If i turn it down, almost no sound comes out, if i turn it all the way up the gain is devastating and the distortion crackles and self oscillates... The tone changes a bit as well, but not much like in the HM-2 bass knob. :scratch:
I separated the MID and HI, and while it's a lot more veratile I couldn't get the exact trademark sounds of HM-2, but still very thick and nice powerful distortion, with familiar type of growl. I did skip the germanium diodes which is probably why the sound is more dynamic and even clears up nicely with the guitars volume pot.

So, still work to do, but i'm a bit excited. :twisted:
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Re: Boss - HM-2 ( Heavy Metal )

Postby dai h. » 23 Apr 2009, 12:10

-sounds awful IMO

-better (good?) for bass

-weirdly seems to sound better through Boss/Roland amps(Cube, JC)
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Re: Boss - HM-2 ( Heavy Metal )

Postby dannybuoy » 27 Apr 2009, 17:57

With the gain at minimum, low all the way up, and high at 1.30, I can get a really cool furry vintage sound on bass that's great for old school Black Sabbath numbers. Turning the gain up past this point and it's Jekyll & Hyde, jar of wasps type of tone - not that that's necessarily a bad thing!
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Re: Boss - HM-2 ( Heavy Metal )

Postby mugician » 27 Apr 2009, 18:55

I took out all the diodes and am using it to devastate the front end of my overdrive. It's absolutely ridiculous.
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Re: Boss - HM-2 ( Heavy Metal )

Postby juni » 28 Apr 2009, 09:49

Got it all working now, had some errors with the gyrator setup. The EQ is now very close to the original, but not spot-on exact for some reason, could it be the opamps...

dai h. wrote:-sounds awful IMO

Yes, it's obviously not suited for everybody or every type of music. I like it though and this 3 EQ version makes it more versatile.

dai h. wrote:-weirdly seems to sound better through Boss/Roland amps(Cube, JC)

Ha! I was actually surprised how well it worked with a microcube...
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