Minisågverket: A simple metal distortion project

[Fancy Lime]

Hi everyone,

what with the state of the world and all, I started revisiting the music of my youth. Particularly Nasum, Krigshot, Skitsystem, Victims, and the like, and I realized that I had no appropriate guitar sound for that sort of thing. I just bought my first guitar a month ago or so, so there was never a need for it. I particularly like the guitar sound of the late great Mieszko Talarczyk on Nasum's 1998 album Inhale/Exhale. While he apparently did not use a Boss HM-2 but a DS-1 into a Fender Dual Showman Reverb into a Marshall 4x12, it sounds pretty dang close to the classic Swedish Chainsaw sound of the HM-2. Entombed"s Left Hand Path would be the reference implementation for the HM-2, if you want to have something to compare to. So I took a look at the HM-2 and decided that that kind of sound can be achieved with a much simpler device. In the end, all you need is a bit of crossover distortion, a metric ('cause Sweden ) $#!+ton of clipping and some deliberately drastic tone shaping. Since I always liked the sound of opamp clipping for high-gain sounds, I went with that instead of diode clipping. The end result of my experiments does not sound exactly like an HM-2, nor is it meant to. It's a different flavor but for the same kind of music/guitarist. It's tailored to my taste but can easily be modded to suit other tastes. It does not have tone controls because it is only meant to have one sound. You wouldn't dial back the Bass or Treble on an HM-2 either, would you?

So enough blah blah, here is Minisågverket:



The layout is unverified at this point. If anyone builds this and can verify or correct the schematic, I shall be most grateful. The Gothic font, if someone is interested, is called Gotenburg (yes, "Gotenburg" not "Gothenburg") and can be obtained for free here: https://www.1001fonts.com/gotenburg-font.html

"Chug" is technically a gain control but only really sounds like a gain control before about 9 o'clock. After that everything is just extremely distorted and you can't tell anymore if it gets more distorted. After 9 o'clock, the most noticeable effect it has is increasing the bass, so palm muted chords get fatter and, at some point, fuzzy. What setting gets you the appropriate metal distortion depends strongly on the pickups. Chug on full gets you there with a low power bridge single coil; for anything else, backing of a little may be wise. So the Chug control is mostly there to adjust the pedal to your pickups, not to have different sounds. You might want to use a trim pot instead of a normal pot. Therefore the Layout is such that you can use an in-line trim pot here.

"But Andy", I hear some of you cry, "you forgot the switching circuit!" No. No I didn't. This thing is for music where you NEVER turn the distortion of and it goes straight between guitar and a very(!) loud, clean amp with no other shenanigans. If you think your music needs more than one guitar sound, this is not for you. Ok, ok, I'm being overly dramatic. You can add a switch if you want but I'll have nothing to do with it.

Some haphazardly recorded sound samples:
https://www.aronnelson.com/DIYFiles/up/MinisagverketDemo.mp3
Not a guitar player -> Yamaha Pacifica 311 -> Minisågverket -> Focusrite Scarlett 2i4 -> Audacity. No post-recording modifications of any kind. First Riff: bridge humbucker, Chug at 10 o'clock. Second: neck P90, Chug at 10 o'clock. Third: bridge humbucker, Chug full. Fourth: bot pickups, Chug full. The fadeout at the end of each is done with the Volume pot on the guitar. It may be worth noting that the bridge humbucker has a very low output, much less than the P90, noticeably less than a PAF. I will replace it with a Dimarzio Super Distortion at some point, which would probably sound much more appropriate for this demo. Maybe I'll do another one then. Unless someone beats me to it, which I would not be opposed to at all.

As always: Please tell me if you find errors and have fun with this thing. Let me know if you need help modding it to your personal needs and tastes.

Yours,
Andy

[amptramp]

It sounds good - with crossover distortion, the distortion increases as the signal gets smaller so you always notice it.

[Mark Hammer]

Interesting.  I like crossover distortion with bridge pickups.  And since the sound relies heavily on asking more gain of the op-amps than they can manage, I'll suggest using 1458s as a way of warming the tone.  Basically, anything with a poor gain-bandwidth product should be good-sounding.

[anotherjim]

I'd agree with Mark. The 1458 is basically a pair of 741's which if you must do it, is one of the best sounding clipping opamps, but you have to bear the noise which can be too much in the decay. The crossover diodes mitigate the first stage noise by gating it out. This could be a case where designing with single amp packages is a good idea to get maximum flexibility.

[Fancy Lime]

Hi Mark, hi Jim,

interestingly, the choice of opamp seems to have very little impact on the sound for this one. I started designing with an NJM2068 because I really like its clipping sound. When the whole thing was done, I swapped it for an NE5532, a TL072, a TLC2262, and an NJM 4556, thinking I would get noticeably different sounds. But TBH, I don't think I could tell the chips apart in a blind test, which is rater remarkable because normally an overdriven TLC2262 sounds nice and fat, almost tube-like, whereas a TL072 sounds like nails on a chalk board, and the BJT types are somewhere in between. But not here. I guess the intense pre- and post-clipping frequency shaping just kills most of the differences. Nevertheless, people should try out different opamps and see if they can spot the difference. My ears just aren't golden enough.

Cheers,
Andy

[ElectricDruid]

You can add a switch if you want but I'll have nothing to do with it.

Lol, love it.

[anotherjim]

I suspect the TL072 sounds ok in this because its inputs don't look like they can be pulled outside their operating range, even when the outputs clip. You have included a divider going into the second stage plus the diode drops so it's +in won't get the full swing from the first stage clipping.
I see the low pass filtering makes op-amp speed almost irrelevant!

[iainpunk]

woah, nice

that sound great!!
funny that i also build a grindcore/deathmetal/crustpunk pedal recently, with almost the same line of reasoning, also incorporating crossover distortion.
although mine has less gain on tap (the gain before the crossover distortion is fixed) and has active tone shaping to sound closer to the chainsaw sound (28dB of boost around 1kHz, thats 9dB more than the HM2 has!!!).

i think building your Minisågverket would be a nice project to add to my grindcore pedalboard!!

[Fancy Lime]

woah, nice

that sound great!!
funny that i also build a grindcore/deathmetal/crustpunk pedal recently, with almost the same line of reasoning, also incorporating crossover distortion.
although mine has less gain on tap (the gain before the crossover distortion is fixed) and has active tone shaping to sound closer to the chainsaw sound (28dB of boost around 1kHz, thats 9dB more than the HM2 has!!!).

i think building your Minisågverket would be a nice project to add to my grindcore pedalboard!!

Thanks!
Yeah, it's definitely more for grindcore, crust and similarly raw styles than for "modern" metal, which always sounds too nice and polished to my ears. Developing this thing was a ton of fun. I am already thinking about the next high gain distortion. This time with a 3-band tone stack. As in "what if the Metal Zone had better tone shaping and controls with less absurd ranges?" We'll see how that goes.

When building Minisågverket keep in mind though that the layout is unverified. I did trace the schematic back from the layout and got the same schematic that I started with, but one is often blind to ones own mistakes. So checking before building is advised. Also: it would be super awesome if you could post a verification (or correction, if necessary) here, once you've built it.

Cheers,
Andy

[iainpunk]

woah, nice

that sound great!!
funny that i also build a grindcore/deathmetal/crustpunk pedal recently, with almost the same line of reasoning, also incorporating crossover distortion.
although mine has less gain on tap (the gain before the crossover distortion is fixed) and has active tone shaping to sound closer to the chainsaw sound (28dB of boost around 1kHz, thats 9dB more than the HM2 has!!!).

i think building your Minisågverket would be a nice project to add to my grindcore pedalboard!!

Thanks!
Yeah, it's definitely more for grindcore, crust and similarly raw styles than for "modern" metal, which always sounds too nice and polished to my ears. Developing this thing was a ton of fun. I am already thinking about the next high gain distortion. This time with a 3-band tone stack. As in "what if the Metal Zone had better tone shaping and controls with less absurd ranges?" We'll see how that goes.

When building Minisågverket keep in mind though that the layout is unverified. I did trace the schematic back from the layout and got the same schematic that I started with, but one is often blind to ones own mistakes. So checking before building is advised. Also: it would be super awesome if you could post a verification (or correction, if necessary) here, once you've built it.

Cheers,
Andy

unholy shit, thats the same feeling i have about modern metal!
it starts to be creepy right now, both building a heavy distortion pedal at the same time, with the same line of reasoning, both utilizing crossover distortion, both of us think that most modern metal sounds to processed and polished... hmmmm...

yeah, im probably building it next week, or maybe i can start on it tomorrow, if i don´t get any big assignments at work. I do still have a left over enclosure but no jacks and no 100k log pots. i think ill opt for a 250k log pot for the volume. i am going breadboard it tonight though.
ill definitely prioritize it over my fuzz with shitty overkill eq project.

[anotherjim]

It sounds good to me too. Nice solid chug and softened top fuzz. I think it sounds a lot nicer than any motorsåg I've heard.

[Fancy Lime]

It sounds good to me too. Nice solid chug and softened top fuzz. I think it sounds a lot nicer than any motorsåg I've heard.

Thanks, man! I would really like to hear it in front of an amp with a cab, though. Maybe someday... In the meantime I'm working on that cab sim.

Andy

[Fancy Lime]

BTW, I was thinking about alternative names for metal pedals. i remembered a thread we had some time ago and typed "The Swedish chainsaw" into www.talktotransformer.com

Here is the glorious result:

"The Swedish chainsaw was fitted with four blades, each with eight cutters. Each cutter was fitted with a screw which could be tightened to tighten a cut. A large rotating blade could be turned on or off and the saw was made so that the blade could be adjusted in the same way as to achieve desired blade spin and cut. The size of the blades was determined as the blade thickness could not be specified using current computer modelling techniques because of the size of the blades. In the 1970s Swedish companies developed machines which could make these blade sizes and use them as template designations. The most commonly known model name for a scalawr saw is the Ettan-Döpfner (SV-Döpf-en-D). This was sold under several names until it changed to the new model number 4500 in 1976.

"The scalawr saw was an important tool for scalawr cutting, but in the past year or two it has been replaced by the high-speed saw (HSW). Although most of the scalawr models are still available, there are also several other models, including the Ettan Döpfner 3, a two-blade model of similar features as the SV-Döpf-en-D but the new saw appears to have been introduced earlier. In 1994, a machine capable of cutting through"

So my next high gain pedal is definitely going to be called the Ettan-Döpfner and will feature a "scalawr" control, whatever that is. Something to do with cutting, I suppose.

Cheers,
Andy

[amptramp]

What gets me is the tremendous lengths people will go to to avoid crossover distortion in hi fi amplifiers because with a lot of program material it sounds horrible but it is a great sound for heavy metal guitar.  It tends to act as its own noise gate so when the note fades away on the guitar, it seems to stop more abruptly with crossover distortion.  I keep having to rethink a lot of ideas that are firmly entrenched in the hi fi world.

[Fancy Lime]

What gets me is the tremendous lengths people will go to to avoid crossover distortion in hi fi amplifiers because with a lot of program material it sounds horrible but it is a great sound for heavy metal guitar.  It tends to act as its own noise gate so when the note fades away on the guitar, it seems to stop more abruptly with crossover distortion.  I keep having to rethink a lot of ideas that are firmly entrenched in the hi fi world.

Not just Metal distortion. I find crossover distortion sounds great with almost any overdrive or distortion that is "seriously distorted", meaning not straddling the brink of distortion. I have done this with back-to-back BAT41 Schottky diodes in Tube Screamer type overdrives and it's great. It adds more apparent drive while leaving more of the dynamics intact. I have never tried Ge diodes but would imagine them to be interesting ass well due to the (often) softer knee. The noise gate effect is definitely a bonus. Having a cap to ground after the diode pair (like C7 in the schematic of the first post here) makes the noise gate much more effective for hiss frequencies. Right choice of value is a bit of trial and error, though. Should be large enough to kill as much noise as possible when the diodes are closed but small enough not to cut too much treble when the diodes are open. Depends on the diodes, obviously. Easier wit low-leakage diodes. I am amazed this is not done more often. Even more amazed that there are tons of really noisy high gain pedals out there for no good reason.

Andy

[jfrabat]

I am giving this thread some CPR and resuscitating it!

Was finishing up some old pedals, and I came across a printout of your layout and schematic.  So, naturally, I decided to give this pedal a shot.

Started with the breadboard.  Kind of funny, because I added an LED to it to see when it was on.  I guess your comment on the stompswitch and how this pedal is NEVER off was correct, because I had issues, and it was caused by the CLR leg touching the leg or R9!  LOL!  Anyway, corrected it, and I liked the sound, so I decided to build one.  Seeing as no-one has verified the layout, I am giving it a shot.  Board is populated, by the way, but still need to connects pots and jacks (and stompswitch...  yeah, yeah, I know...).  Will report back when finished building.

[Axldeziak]

I drew up a layout and posted it about half a year ago because it was almost impossible for me to make out the layout on the original schematic:
http://guitar-fx-layouts.42897.x6.nabble.com/Minis-gverket-A-simple-metal-distortion-project-td47957.html
The layouts have been corrected and verified.

I'm uploading it here as well.

[Mark Hammer]

RE: changing the opamps.

I've increasingly come to take the view that, in some instances, what we are hearing is the sound of an op-amp that has simply run out of headroom, subsequently getting re-clipped with diodes.  Given that the "Chug" control can theoretically increase gain by as much as 1000x, even very modest settings of the control exceed the headroom of the op-amp used, when powered with 9VDC.  So, while a superficial glance would suggest that "all" it does is crossover distortion, in fact the crossover distortion from the 1N4007 pair is simply supplementing the hard clipping produced as higher gain settings run the signal smack up against the ceiling on voltage swing.

All of which would suggest that, yes, in an application like this, varying the op-amp type can make an audible difference.

[jfrabat]

Finished the board, but I have issues (I do not think it is the layout).

First time around, no sound even in bypass.  Corrected that.  Then no sound when engaged (a resistor leg again rubbing, this time with a diode); fixed that.  Then sound was going through, but it sound was way off (lots of interference).  Thought it was a bad solder or something, so I went through the board once again with the soldering iron; now I don;t get sound once again...  Must be a solder bridge somewhere, but I can't find it!

Here's the overall shot:



Board (component side):



Board (copper side, after latest "fix"):



Stompswitch:



Voltage check confirms a short... I get 9.5V at source, but if I change the negative lead to the ground at the jacks, voltage starts fluctuating and never goes near 9V.  I have to take my time with this one (of course, eyesight going down the drain makes finding these harder and harder!)

[duck_arse]

I can't see it good enough, but I thimk you have one of your jacks wired signal to sleeve. check resistance between the sleeve and the other sleeve.