Friday, 2 May 2014

Boss HM-2 Heavy Metal

And for those who DO want the chugga chugga crushing lows! :o)

And I didn't expect it but this will fit in a 1590B too (doh!) so the Lite version may not get built quite as often now.  But still a good exercise in adapting these things and I'm glad there is a more compact version available if someone wants to use it.

This one has also been verified by our resident Finnish metal head who sent me a comparison clip against an original and it sounds identical to me, so you're good to go on the build!  Thanks again to Miro, the building machine! :o)

Here's the clip, so you can guess which is which




Info about the original:

The HM-2 is a distortion effect specially designed for Heavy Metal music.  In spite of its compact body, it features an extremely wide dynamic range, therefore allowing rich, dynamic distortion sounds.  Also, the HM-2 can be effectively used even with a single coil pickup guitar lo low output level, because of its high gain.  Wide variety of tone color creation is made possible with two Color Mix Controls.

Why aye bonnie lad, blondegraemey's demo:







And after the discussion below, a modded version with additional mids pot.



58 comments:

  1. The original is the first one, and the clone, the second. Am I wrong? :P

    They sound quite similar, but there's a slight difference between, as the first sounds rouder to my ears.

    Love this pedal, and even thougt I have an original Boss HM-2 will surely build this board just for the sheer pleasure of building this great effect!

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    1. Didn't want to reveal it so quickly :) You are correct. My circuit is only connected to a test box, so that could also make a difference. I think i'm going to box it up tomorrow. My bench recording equipment is crap, so the clip is not too hi-fi due to that.

      Either way, the differences in sound are very, very small, considering that all the semiconductors are different from the original (and i used 2µ2 cap instead of 1µ5). Since the semiconductors i used for the Lite version worked so well, i used the same ones for this - 3x LM358 for dual opamps, BF245A, C3198 and A733 for transistors. None of those are exact equivalent to the ones used on the original (except for the JFET). I think this is the best circuit for those LM358s due to their (otherwise annoying) tendency of adding brutal distortion on their own. That being said - i never got them sounding good in any overdrive design..

      This is a great distortion, but the idiotic ACA power supply requirement on the original sucks. And modding is out of the question, 'cause i want to keep its value. So building a clone is a lot better option than paying 120€/£100/$160 for a used unit. Especially now that Mark did the impossible and squeezed the circuit in 20x26. 1590B is smaller than standard Boss enclosure...
      Of course the original is nice to have, if you can get one for reasonable price. Got mine from london for ~£52 - so obviously i had to buy it.
      +m

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    2. Yeah, ACA sucks. To tell you the truth, the HM-2 is the only Aca Boss pedal that I have not modified still to use regular +9v adaptor (my DF-2, CS-3 and DS-1 have been modified)

      I think that I have a few LM358 somewhere, so i'll build the board with these ic's.

      By the way, I had to do a long research, but I finally purchased my Hm-2 for 40 euros, shippin' included. Have to tell too that I was asked even 175 euros for units of similar age and use, sheer madness for this effect!

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    3. By the way, if anyone's interested, Spain is a cool place to buy this effect, and similar ones, like the HM-3 or the MT-2, as many "guitar gurus" in my country tell that these effects really suck, so to be cool in forums and websites, you have to say that "Boss HM-MT are pure crap" and the second hand market is really interesting for these Boss effects, being 60 euros an usual price.

      Same with some other pedals and amps. My Valvestate 8100 head was just 100 euros! :P

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    4. I do think MT-2 sucks :) I have two of those and i'm currently trying to sell the other for 40€, but no luck yet. Had to get new EQ pots for it, so i'm not letting it go for anything less.

      Been planning on getting HM-3 and ML-2 for myself, but i have not come across good deals on them so far. Anyone want to trade MT-2 for HM-3 or ML-2? :)

      Got myself a '85 DF-2 recently. The guy who i bought it from thought it was broken due to ACA supply requirement.
      MD-2 is great by the way... especially when paired with a chorus. DS-2 isn't bad either.

      I'm not a fan of Boss pedals, but those seem to be accumulating on my collection - http://mirosol.kapsi.fi/collection/boss/

      But back to the subject...
      HM-2 has unique, strong middle with massive lows and even the highs are clipped in a lot neater manner than on most metal distortions. I think it is unique, as i don't currently know of any other circuit with similar, dual high Q filters. Nor anything that sounds even remotely the same. Makes me wonder why Boss didn't continue producing it. Even after the swedes made it a cult classic in late 90's.
      +m

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    5. I have a Boss MZ-2 Metalizer... I still love this pedal although I rarely use it other than in the studio. The built in doubler and chorus was handy at times. These were made in Japan and only for a short time.

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  2. I read somewhere that in the tonestack, the high knob also controls the mids. The relevant mids circuitry is tied to the highs. Any idea how to detach the mids into a separate mids control?

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    1. ...by creating a third active gyrator filter for mids and changing the high Q point of the original high gyrator.
      So no. I don't think it can be done in any easy, simple way.
      +m

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    2. I just found the schematic. There are three active opamps used for the Q. Two are linked to HIGH and it might be that one of these deals with mids and the other highs. The remaining opamp is linked to LOW so that is obvious.

      I do not know if one of the opamp controls the mids. I am guessing here. If we separate the 0.1uF output and 0.15uF outputs, linking one of these outputs to lug 2 of a new B10k pot with lug 1 going to + of the volume recovery opamp and lug 3 going to - of the same opamp (wired like the existing knobs) might give us a MID control.

      Again, I am guessing here. On lvlark's layout, if we move the bottom leg of the 100n cap moved up 3 rows to just above Low 2. This 100n might control highs so I am moving the HIGH 2 wire to this new row. The old HIGH 2 becomes MID 2 in a new B10k pot. MID 1 is connected to HIGH 1 & LOW 1. MID 3 is connected to HIGH 3 & LOW 3.

      Again, all purely guesswork...

      Can someone educate me on how a gyrator filter works? Thanks!

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    3. Gyrators are covered on this article:
      http://www.geofex.com/Article_Folders/EQs/paramet.htm

      I have no idea if that will work...
      +m

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    4. Yes that makes sense to me, and working out the frequencies it seems that the 150n cap will go to the Mids 2 lug. Check out this Excel file which is from the spreadsheet I keep all of my parts logged.

      http://www.filedropper.com/calcs

      There are a few calculators that I use in there which others may find useful and one for gyrators

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    5. Although there is some slight difference, the footswitch click gave away which was which... :)

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  3. Wow Mark, this is the best HM-2 vero out there. Well done!

    I just got an extra tall board from MKLEC that would suit this perfectly

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  4. This is very, very cool. Thank you so very much! I will build this very soon and compare them to my '84 MIJ and' 89 MIT, which does have a very minute difference in their sound. Tbh I also ordered the Behringer HM300, and might as well make one huge 'scientific' comparison.

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  5. This is very, very cool. Thank you so very much! I will build this very soon and compare them to my '84 MIJ and' 89 MIT, which does have a very minute difference in their sound. Tbh I also ordered the Behringer HM300, and might as well make one huge 'scientific' comparison.

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  6. Oh, hehe. I just watched the video, and he says that the sound on MIT and MIJ are the same... well, not quite ;) the nature of the tone sure is similar, but the mid bump on the MIT is 'sharper' kinda, anyways, if one listens closely, the difference is clear. As stated above, i'm gonna make a thorough comparison with frequency analysis and maybe som oscilloscope shots and what not.

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    1. The thing is, with this and a lot of similar pedals, you could almost certainly find exactly the same differences between two MIJ pedals. The frequency response from the gyrator could shift noticeably if maybe a cap with a 10% tolerance was used and one was at the upper and the other at the lower end of the tolerance scale. These are the figures based on the 150n cap:

      Lower tolerance 135n - 915Hz
      Upper tolerance 165n - 828Hz

      So an almost 100hz difference in the mid point frequency response using exactly the same cap. If the cap had a 20% tolerance the difference could be as much as 180hz.

      I think the important thing here is that if you want to fine tune the frequency response to get slightly more or less lows, mids or highs, then it's pretty easy to do no matter which version of the pedal you have. Just change a cap or two.

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    2. Hi Mark,

      Thank you for your answer. And yes, your statement seem very likely to be the case in point here :) Never thought of the tolerance being high enough to affect the tone in such a pronounced manner. It is surely worth experimenting with.

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    3. I just had another look at it and think swapping the three 330R resistors with multi-turn trimmers would be great for tweaking the frequency response. If you use 500 ohm multi-turns preset at the 330 ohm value of the resistor and then tweak from there. Set to 500 ohm (using the mids gyrator as an example) the frequency would be set to 705hz, set to around 250 ohms it would be around 1khz. So I think that would be a really precise way of setting this up exactly how you want it in all 3 bands.

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  7. 5 pot version added with additional mids pot.

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    1. Thanks for following through on my Mids question! Much appreciated. That 330 ohm resistor seems to make a significant difference. I might have to use your (very useful) calculators to work out the EQ ranges.

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  8. How does this pedal compare to a metal zone MT 2?

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    1. They are nothing alike. :) Controls are completely different and the clipping textures are from different planets.

      Personally i think MT-2 wouldn't be worth drawing a layout, nor building it. There are six pots and the circuit is even bigger than this, so it would be real pain to squeeze in 1590B. Plus cost of the parts would be more than a used unit. One just went for 29€ on ebay.
      You can buy one use MT-2 off from me if you want to :)
      +m

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    2. Thanks, but I have an MT-2! :-p
      That's why I was asking, I can get some nice lead tones out of it drowning it in chorus an delays and sending it through a clean solid state amp, I tried to plug it into my freshly built madamp a15 and just cannot find a use for it, even though it has a wicked tone stack, the two kinds of clipping just don't play nice together ... I'm trying to find something that will ...

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    1. A layout of this with the pinout for the M5216L layout would be great, since I have a bunch of them. since all 8 pins are in a line and it's not a DIP package.

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    2. I know anyone who has the SIP version of the IC would also like this, but I don't think it's going to happen to be honest John. I've done a SIP8 layout before for the Eternity and I can tell from that experience that the layout would essentially need re-doing from scratch apart from the top 8 rows that the transistors are on, which would be awkward and take time in order to accommodate an unusual IC that most people won't use, and isn't necessary to use anyway as the M5216L can also be obtained in a DIP8 package.

      If you do want to build it with the original inline IC I'd suggest some sort of SIP8 to DIP8 converter, or even make one on a small piece of vero or perf and use this kind of inline connector to mount it in a DIP8 configuration.

      http://www.ebay.co.uk/itm/191024596739

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  10. Is there any good substitute for the 2SA970?

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    1. Any silicon PNP with same pinout should be fine. 2SA733 is what i used and it's working well.
      http://www.taydaelectronics.com/t-transistors/other-transistors/2sa733-transistor-pnp-50v-100ma-nec.html
      +m

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  11. Ok, i finally got around to do some soundclips :) This is only for the die-hard HM-2 fans thogh, i guess.

    http://www.tonetroll.com/2014/05/boss-hm-2-vs-behringer-hm300.html

    Now i need to build one, and see how it compares to the other ones in my possession.

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  12. Just got this one working. Needed to knife those tracks! You know those really tiny beads of solder that get caught between the tracks and cause a short..

    This circuit is awesome as we all already know. I just love this badass layout

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    1. Glad you got it going buddy :o)

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    2. Haha thanks. I've been wanting one of these forever so it's great to build one.

      It has exceeded my expectations. My first impressions are pretty much love at first chugga chugga skree

      I've got some Dano pedals that I think are copies of the Metal Zone and this HM-2 is much more clear and natural sounding but still totally mangled and heavy

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  13. Hey! I stumbled across your page while looking for info on replacing the H color potentiometer. The H pot on mine is completely broken. I called Boss, and they no longer sell the part. Any info on this part would be greatly appreciated. Thanks!

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  14. Hi just built this. I used TL072 ics, socketed. There was a high pitched whine, sometimes worse. Removing the ones for the tone controls got me back to the plain overdrive sound, with no whine. Replacing those with 4558(?) from tubescreamer spares stopped it! Can some ics be bad, or is there likely some other problem with my build I've just covered up with the new ics? Thanks!

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  15. I'm disappointed that no-one has mentioned Sunlight Studios or Entombed yet :/

    The 2nd hand market for this pedal is INSANE. I just bought a Behringer HM300, which is supposed to be a modern reissue, and for the £19 i shelled out, its one hell of a clone even if it is pink!

    At some point however, I would like to put this together and test out the Mids mod.

    Oh and please... the HM-2 and MT-2 are NOTHING alike. Basically got to Youtube and listen to the guitar sound on Entombed's Left Hand Path (or any other 90s Swedish death metal for that matter) and find out why this pedal is so sought after by Death Metal guitarists and bass players.

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    1. It depends... I had mine for 35 € (second hand) :P, just time and patience.

      J.

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  16. Hi there, congratulations for your work!

    I have an old HM-2, and want to try de Mid Pot. Is there also some way to add another pot for tweak de Mid Freq, like the concentric pot in the MT-2? Would it be in the place of the 330R resistor linked to the 150n that goes to the Mid 2? If it's possible, what would be the value? Thank you very much.

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  17. Does it say somewhere that I missed what kind of transistors I need? I assume 2 different types. I've got a handful of transistors but I don't know what I'm looking for or like what ranges/style/etc.

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    1. See where it says Q1, Q2 and Q3? Those are the transistor model numbers. There will likely be equivalents you can use instead, so check through the thread above and maybe Google ' HM2 transistors' or something.

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    1. Measure all the transistor and IC pin voltages and post the results. That will give us the best clue if something looks amiss.

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  19. hey! i dont know if its possible, but i want to make this pedal without not pots, because i only want to use it with all pots at max. is it possible with this layout somehow?

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    1. dist is a 250k pot.
      take a 250k resistor, and solder it between dist1 and dist3 wires.then connect dist2 to dist3, and now you have dist maxed out for ever!do the same thing with the other pots and you're good to go.

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    2. thanks, i will start it soon

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  20. Hi,

    maybe I am doing something wrong but I hear loud radio static when turning mids knob...can someone detect where is problem? also lows and highs don't make to much of difference in tone when used...what can be wrong? Distortion is present and volume pot is ok.

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  21. I built this a while back and it sounds great but I would really like to add some clipping options to it I am just not sure which diodes to swap out. anybody have any experience or ideas which diodes i should pull? I appreciate any feedback thanks guys

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  22. This looks awesome! I've read that it fits inside a 1590B enclosure, but would it fit inside an original Boss HM-2 case? I was lucky enough to have somebody send me the case and the original pots, but would it be possible to put this vero build in the boss case? Cheers guys :)

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    1. Should fit, yes, but you'll need to figure out what to do with the bypass switching. This layout is intented for true bypass and 2PDT/#PDT stomp...
      +m

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  25. Hi guys, I want to build this pedal, but I see that this layout ask for 100K pots for L and H color knobs and according to a schematic that I saw they should be 10K linear pots. Is that correct?

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    1. I've just checked it and I think you're right, God knows how that one got through the net when I did it so long ago and when quite a few people have built it. I assume the frequency response must still be usable. I'll end it and update, thanks for the heads up.

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  26. Built this using the now outdated layout with 100K lin pots for L and H colour, I'll swap them out when 10K pots arrive. Sounds really good anyhow, I used BF245c, 2SC2240, 2SA733 and TL072 ic's. I had a handful of M5216L SIP ic's and so I built a daughterboard to interface them to this layout using the associated datasheets as reference for pinout. Unfortunately it was obvious something was not right, it sounded like a quiet crackly mess! Maybe they were fake M5216L chips, not sure what happenned. TL072's sounded great so I'll stick them back in. Thanks for the layout!

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