Boss - HM-2 Heavy Metal  [schematic]

All about modern commercial stompbox circuits from Electro Harmonix over MXR, Boss and Ibanez into the nineties.
User avatar
Freppo
Breadboard Brother
Information
Posts: 56
Joined: 14 Sep 2013, 12:37
Has thanked: 15 times
Been thanked: 117 times

Post by Freppo »

Hmm.. I can't edit my posts for some reason?

Anyway, I was trying to embed this video:


I filmed it today with my ipad.. it's my vero layout (through a breadboard, i'm using trimmers insted of post for testing)
I'm using 50K log pot for volume to let alittle more volume through.. Also, I found that a A20K pot works better for gain.
Check out my building blog at http://www.parasitstudio.se

User avatar
macsniper
Information
Posts: 3
Joined: 19 Nov 2013, 15:01
Has thanked: 1 time
Been thanked: 1 time

Post by macsniper »

Freppo wrote: Hi!
Thanks for spotting the error, correcting it actually helped with reducing the oscillation I had problems with earlier. :D :thumbsup
The fix was very easy, just move the positive leg of C3 down to row F. I will update and post the changed layout soon.
Now it's working 100% for me.
No problem, I do my very best ;)
Freppo wrote: Strange that you get 1.7v at the voltage divider.. I hope you find the problem.
At least I fixed that problem now, I get something like 4.6V with 9.3V at the battery. Nevertheless, the sound just dies after the first capacitor, and I have no clue why. Maybe I'm using audioprobe wrong, or maybe the transistor is dead... gotta keep trying, I NEED the death metal saw sound...

User avatar
macsniper
Information
Posts: 3
Joined: 19 Nov 2013, 15:01
Has thanked: 1 time
Been thanked: 1 time

Post by macsniper »

Ok, my HM2-Clone is working now, except the same issue you had with high gain levels. What value did you use for C5?

User avatar
Krakenpine
Information
Posts: 1
Joined: 18 Dec 2013, 18:20
Been thanked: 1 time

Post by Krakenpine »

Wait. What's with the D1 and D2. In the layout they are parallel when in the schematic they are in series. That could explain some of the sound differencies because the distortion is symmetrical instead of the asymmetrical of the original.

User avatar
Freppo
Breadboard Brother
Information
Posts: 56
Joined: 14 Sep 2013, 12:37
Has thanked: 15 times
Been thanked: 117 times

Post by Freppo »

macsniper wrote:Ok, my HM2-Clone is working now, except the same issue you had with high gain levels. What value did you use for C5?
I decided that messing wih C5 changed the tone too much, and it only helped with lower gain transistors anyway that didn't sound right, so I kept C5 stock. But another possible solution would be to place a buffer at the input. The original is buffered so I thought that may be the problem with this schematic? Maybe a buffer is really needed.

First try a buffered pedal in front of the circuit and see if that helps.

Here's a layout for a really simple but nice buffer that is small enough to fit together in a 1590BB
download/file.php?mode=view&id=23156
Krakenpine wrote:Wait. What's with the D1 and D2. In the layout they are parallel when in the schematic they are in series. That could explain some of the sound differencies because the distortion is symmetrical instead of the asymmetrical of the original.
Well spotted sir! You are correct. I doubt it should matter much since there are so many stages of clipping and both ways are asymmetrical, but if you want to build it 1:1 with the schematic you could just solder two diodes together standing up. Thanks for the headsup though :thumbsup

cheers
/ Fredrik

ps. Sorry for my late reply, I had totallt forgotten about this thread]
Attachments
JFET Buffer.gif
JFET Buffer.gif (10.63 KiB) Viewed 6711 times
Check out my building blog at http://www.parasitstudio.se

User avatar
Slabbefusk
Information
Posts: 11
Joined: 19 Mar 2011, 10:50
Been thanked: 1 time

Post by Slabbefusk »

GodSaveMetal wrote:
Slabbefusk wrote:At first I put a 2N5551 instead of the 2SC224 and a 2N5401 instead of 2SA970. I don't know why i picked those replacements in the first place, I guess I trusted google too much. Now there is a BC547 where the 2SC2240 is originally and a BC557 instead of the 2SA970. Is there no editing function on this forum? :?
Please note hte 2SA970 is a PNP E-C-B and the BC557 is a PNP E-B-C watch the pinout!!!! :hmmm:
Also the 2SC2240 is a NPN E-C-B and the BC547 is a NPN E-B-C watch the pinout!!!!!!!!!!! :?

Please read all my recomendations and changes!!!!!!!!!! :twisted:
I will read your recommendations :) .

And yes I was aware of the change in pinout so I just flipped them around and it worked fine. My friend who I built it for had some issues with noise though which I believe stem from the fact that his wallwart is a switching supply with switch frequency in the human hearing range. It worked fine with a battery just a little low on the gain.

I will build more of these with a better layout and try to find the monolithic op-amps as well as make an all SMD version.

User avatar
GodSaveMetal
Resistor Ronker
Information
Posts: 299
Joined: 19 Sep 2009, 16:11
Has thanked: 138 times
Been thanked: 55 times

Post by GodSaveMetal »

Slabbefusk wrote:
GodSaveMetal wrote:
Slabbefusk wrote:At first I put a 2N5551 instead of the 2SC224 and a 2N5401 instead of 2SA970. I don't know why i picked those replacements in the first place, I guess I trusted google too much. Now there is a BC547 where the 2SC2240 is originally and a BC557 instead of the 2SA970. Is there no editing function on this forum? :?
Please note hte 2SA970 is a PNP E-C-B and the BC557 is a PNP E-B-C watch the pinout!!!! :hmmm:
Also the 2SC2240 is a NPN E-C-B and the BC547 is a NPN E-B-C watch the pinout!!!!!!!!!!! :?

Please read all my recomendations and changes!!!!!!!!!! :twisted:
I will read your recommendations :) .

And yes I was aware of the change in pinout so I just flipped them around and it worked fine. My friend who I built it for had some issues with noise though which I believe stem from the fact that his wallwart is a switching supply with switch frequency in the human hearing range. It worked fine with a battery just a little low on the gain.

I will build more of these with a better layout and try to find the monolithic op-amps as well as make an all SMD version.
Please post some pics of this!!!!!!!!!!!! great man!!! the lay is OK!!! superverified!!!!!!!

User avatar
loylo
Breadboard Brother
Information
Posts: 63
Joined: 23 Jun 2011, 08:05
Has thanked: 12 times
Been thanked: 20 times

Post by loylo »

Hi GodSaveMetal!

I own an old HM2 and the PCB is pretty destroyed by all the mods that had been made.
I'd like to do a new PCB so your work is quite helpful.

I have printed your layout, and the problem is that the size of the PCB is a little bigger than the original PCB, so it don't fit in the original box.
Can you share all the files (Eagles or whatever the software you used to make your layout) sothat I could adapt the layout to the original box, please?

User avatar
matt239
Solder Soldier
Information
Posts: 228
Joined: 11 Sep 2010, 18:54
Has thanked: 60 times
Been thanked: 5 times

Post by matt239 »

Do the first stage transistors clip?
Or are they just clean boost?

How would we mod that section for less gain?

User avatar
darvinya
Information
Posts: 1
Joined: 19 Feb 2014, 20:05

Post by darvinya »

loylo wrote:Hi GodSaveMetal!

I own an old HM2 and the PCB is pretty destroyed by all the mods that had been made.
I'd like to do a new PCB so your work is quite helpful.

I have printed your layout, and the problem is that the size of the PCB is a little bigger than the original PCB, so it don't fit in the original box.
Can you share all the files (Eagles or whatever the software you used to make your layout) sothat I could adapt the layout to the original box, please?
Hi

If you still have the circuit board, then Solder out on all plastic parts and scenneld (not a photo of!) On both sides. Add it up and do it improved the mucus.

User avatar
Drachir_6
Information
Posts: 1
Joined: 28 May 2014, 16:57

Post by Drachir_6 »

Anyone got any tips on how to make HM2-style circuits more usable gain-wise? I have a DOD Americal Metal and find that even with the gain at 0 it's incredibly distorted. Swapping the pot seems the easiest approach but should I make it a bigger or smaller value? Cheers!

User avatar
IvIark
Tube Twister
Information
Posts: 2235
Joined: 01 Jan 2008, 23:59
Location: Manchester UK
Has thanked: 562 times
Been thanked: 586 times
Contact:

Post by IvIark »

Forgot to post these:

Image

and a version with an additional mids pot

Image
"If anyone is a 'genius' for putting jacks in such a pedal in the only spot where they could physically fit, then I assume I too am a genius for correctly inserting my legs into my pants this morning." - candletears7 - TGP

User avatar
Pedal Dan
Information
Posts: 24
Joined: 09 Nov 2011, 14:05
Location: The City of Brotherly Love
Has thanked: 1 time
Been thanked: 1 time

Post by Pedal Dan »

soulsonic wrote:Am I one of the only ones who likes the STOCK HM-2 sound? :cry:
C'mon guys - this sound is awesome:
Me too. Although... I've been enjoying the new DS-1X.

User avatar
x-tn
Breadboard Brother
Information
Posts: 68
Joined: 24 Sep 2009, 22:34
Has thanked: 214 times
Been thanked: 37 times

Post by x-tn »


User avatar
Slabbefusk
Information
Posts: 11
Joined: 19 Mar 2011, 10:50
Been thanked: 1 time

Post by Slabbefusk »

As I wrote earlier in the thread I will make an SMD version of this pedal. Everything except the transistors will sized down. I managed to find a source in Sweden for the transistors. The OP-amps will be the classic 4558.

Will post pics when there is more work done!

User avatar
Slabbefusk
Information
Posts: 11
Joined: 19 Mar 2011, 10:50
Been thanked: 1 time

Post by Slabbefusk »

I don't know if I should add an edit to my previous post or just go for it. So here goes.

I've bought some 2SC2240 and 2SA970 trannies but they come in two variants, the BL and GR ones. The thing that differs is the hfe. What kind have you guys used when building your clones? :scratch:

User avatar
IvIark
Tube Twister
Information
Posts: 2235
Joined: 01 Jan 2008, 23:59
Location: Manchester UK
Has thanked: 562 times
Been thanked: 586 times
Contact:

Post by IvIark »

BL and GR signifies the gain range in the transistor (GR: 200-400, BL: 350-700). I don't know for sure with the HM2 but the HM3 definitely used GR variants so I would assume the same was true for the HM2.
"If anyone is a 'genius' for putting jacks in such a pedal in the only spot where they could physically fit, then I assume I too am a genius for correctly inserting my legs into my pants this morning." - candletears7 - TGP

User avatar
Slabbefusk
Information
Posts: 11
Joined: 19 Mar 2011, 10:50
Been thanked: 1 time

Post by Slabbefusk »

IvIark wrote:BL and GR signifies the gain range in the transistor (GR: 200-400, BL: 350-700). I don't know for sure with the HM2 but the HM3 definitely used GR variants so I would assume the same was true for the HM2.
Thanks for the reply! I just got a kit called "The Swede" which is an HM-2 clone as well. It uses a 2N3904/3906 pair instead of the 2SC2240/2SA970. The 2N3904/3906 have very similar gain to the GR variants. Will build both the kit and my own to see if there is any difference!

User avatar
Pruttelherrie
Solder Soldier
Information
Posts: 248
Joined: 18 Feb 2011, 19:35
Location: The low lands
Has thanked: 46 times
Been thanked: 96 times

Post by Pruttelherrie »

Shameless Selfpromotion Alert!

One of my bands just released our second EP on tape. Actually we didn't release it, it escaped, but that's just details. Oldschool Swedish Death Metal.

Listen here: https://rottencasket.bandcamp.com/album ... d-by-filth

One guitar is HM-2 into ENGL Savage 60, the other is HM-2 into Marshall DSL100H. Recorded at home, mixed by Jimmy from Entrails.

The first EP was ENGL e530 into my HM-2-filter (see earlier in thread) and that into ENGL e850; 50%/50% mixed with HM-2 into Marshall JCM900, for both guitars.

Image

User avatar
Blitz Krieg
Breadboard Brother
Information
Posts: 81
Joined: 18 Feb 2014, 10:57
Has thanked: 534 times
Been thanked: 2 times

Post by Blitz Krieg »

swedish hm-2 style?

that's a thing?

brutal

Post Reply