Grinder: a Metal pedal and giving back to this community

[ahermida]

Someone today emailed me concerning the Grinder pedal I developed (check my website for a few audio clips).  I don't want to give out the actual schematic of the pedal but I still want to help anyone interested in making pedals for metal music.  Most of the stuff is usually developed for rock or blues.  Us metal fans are always forgotten.  

The idea behind the Grinder is simple.  Here's what I emailed someone from the forum:

Thanks for the feedback...there's really no magic to the Grinder pedal.  Tony Cole has made 2 other clips that sound better than what I have in the site right now (they will be posted in a day or two).

*  Put 2 distortion sections in series i.e., 2 Distortion+ stages or 1 TS and 1 Distortion+ in series...you can even try a booster going into a distortion stage.

*  put a treble control similar to the Rat (resistor in series with the signal and a .0033uF to ground or 4.5V).  I'm not too fond of tone stacks.

* The final stage is a parametric EQ.  There are a few 1 band parametric EQ circuits out there.  The band should be tuneable between 50 Hz to 500 Hz.  The circuit should have a boost/cut pot so the user can decide how much of the specific frequency to add or take out

*  Don't get carried away with complexity...go for the simplest circuits you can make.  

* You need 2 stages because one stage is NOT going to give you the crunch you need...remember this is a Metal pedal not a weak overdrive.

* Why a parametric EQ as the last stage? I really want to be able to boost a specific frequency in the low end (50 Hz to 500 Hz).  A long time ago I was looking at some patents from an amp maker and they were presenting different cabinet models.  I noticed how you would get a peak at certain low frequencies...well, with the parametric EQ you can actually dial in the particular frequency to enhance your amp.  At this point I don't care what specific freq. value it is since I can dial that and enhance whatever my amp is doing...I let the ear decide.

* On the same topic...most metal pedals out there are very weak on the low end response...the Grinder is NOT...trust me  :!:

* another main concern is to be able to plug this in a clean amp and get the metal sound without having to drive the amp to get there.  You may want to consider putting some assymetric clipping if the clipping stage(s) are still too controlled for you.

Alf
www.hermidaaudio.com

[Paul Marossy]

"another main concern is to be able to plug this in a clean amp and get the metal sound without having to drive the amp to get there."

That's my approach. With a really high gain pedal, I don't want the amp to drive things too much, because feedback can become a real problem in some situations.

[RDV]

I've been trying to come up with a one band parametric to do it using R.G.'s http://www.geofex.com/Article_Folders/EQs/paramet.htm#variable_l, but it seems to require an input/output buffer + a buffer for each stage. I'm gonna try to draw one up but I guess it'll either take a dual OA & a single OA, or a dual OA for the in/out buffers & a half a dual for the one filter section & use the other half as a volume recovery circuit(though I've got to think with all these buffers you might not need one, maybe a switchable lead boost instead?).

Jeez Louise!

RDV

[RDV]

Will this work, Alf, R.G., anyone?


T.I.A.

RDV

[Paul Marossy]

So, would this circuit use (3) single opamps?
Looks interesting.  

[RDV]

So, would this circuit use (3) single opamps?
Looks interesting.  

Or a dual & a single, or 3/4 of a quad. :shock:

RDV

[Paul Marossy]

I have a few TL084s that were given to me. Maybe I could use them in for this circuit... Probably a dual and a single would be better. That way I could find a quieter combination. I dunno, I guess I'll try the quad first.

Have you actually built this circuit, or is it just conceptual?

[RDV]

Conceptual, taken from Geofex. I've PMed R.G., asking him to take a look to see if it's right. His original drawing had two bands, so I removed one and inserted the correct values(hopefully) for what I need.

RDV

[Paul Marossy]

Ah, OK.

[RDV]

Paul:

If you'd like to breadboard to confirm, that would be very cool.
I still haven't bought one of those things. :oops:

RDV

[Paul Marossy]

Maybe that could be my "project of the week".  :wink:
If I do breadboard it, I'll let you know how it turns out.

[RDV]

From Alfonso Hermida:



Regards

RDV

[petemoore]

I think this is what you're trying to implement in the HM pedal...
 I would like to find something that boosts [or allows to pass] a narrow frequency band, in the bass department...a tunable frequency band would be nice too.
 Having not done alot of circuit hacking and splicing, or Parametric building, I don't really know where to start.
 It would just be fun to play around with and see if I can come up with something cool.

[Transmogrifox]

Something I found that adds some deep 'crunch' to my amp, and also to my overdrive pedal is a high-pas filter with a Q of ~10 or 14 with the center frequency set at about 80 Hz.

I actually found it can be used pre-distortion because the typical distortion pedal rolls off the lows so much, there is a mild recovery from the low resonant peak at the 80 Hz range, but the peaking is narrow enough that it doesn't boost enough lower frequencies to make it sound muddy.  With excessive gain on the filter and roll of the highs some, it will turn your tube amp into a muffy fuzz, though.  Very smooth.  I like it.

[RDV]

I think this is what you're trying to implement in the HM pedal...
 I would like to find something that boosts [or allows to pass] a narrow frequency band, in the bass department...a tunable frequency band would be nice too.
 Having not done alot of circuit hacking and splicing, or Parametric building, I don't really know where to start.
 It would just be fun to play around with and see if I can come up with something cool.

Yeah, that's going to be the front end of it, then a 1 band bass parametric and a volume recovery stage. I've just got to finish the drawing.

Regards

RDV

[ahermida]

RDV:

  When are you going to prototype this contraption?  I'm curious to see what happens.  My suggestion is to build 1 stage at a time and test it...just to make sure you don't build a "smoke generator".  After you have the clipping stages working then build the parametric EQ as a standalone and test it.  Once you're happy start integrating both.   It may sound tedious but baby steps can teach a lot of things and you'll be able to listen to the subcircuits and tweak them without the effects of everything else.

Alf

[petemoore]

What does a 1 band parametric, focused on a narrow bassy frequency band..schematic look like?
 Having or whipping up clipping sections is N/P. Blending and such experimentation...it would be kind of a fun project to work with this 'focus in on a defined bass freq range...  bass 'always' loads things down by eliminating alot of it, it seems it would be easier to get nice definition in the lower range.
 I'd like to come up with a working model, but I don't know about parametrics enough to mod one for just a bass freguency peak.
 The only way I could think to do it is tuning a low pass filter, and a tunable high pass filter so that all that's left is the fairly narrow band of bass range.
 I suspect parametric, you can set a sharper cutoff...?
 Very interesting, I was thinking of having 'two sides' side chain jacks, so that modules could be used for two chains, or mixed back into one clipper etc.
 I have to figure out how to get a narrow bass frequency pass filtering circuit [words...] hopefully that could be somewhat tunable.
 I'm thinking of using Adjusticator, Tone Controls, different clipping, tone shaping and boost devices as tunable modules, 'sattellites' for trying variations of this concept.
 I feel like I'm behind the ball a little bit on parametrics...I'll go back and try finding some of the reads on it.

[RDV]

What does a 1 band parametric, focused on a narrow bassy frequency band..schematic look like?

Like this(the parametric section of the Heavy Metal Pedal adapted from R.G.'s site ):


Or this(adapted from R.G.'s site with input buffer):


Regards

RDV

[RDV]

RDV:

  When are you going to prototype this contraption?  I'm curious to see what happens.  My suggestion is to build 1 stage at a time and test it...just to make sure you don't build a "smoke generator".  After you have the clipping stages working then build the parametric EQ as a standalone and test it.  Once you're happy start integrating both.   It may sound tedious but baby steps can teach a lot of things and you'll be able to listen to the subcircuits and tweak them without the effects of everything else.

Alf

I don't know Alf. I'm very burned out & have been @ band practice all night. I have been doing two people's jobs @ work & just put together an Easyvibe & worked on this pedal design @ the deficit of sleep or rest of any kind. I know, BOO HOO HOO. :roll:

I'm going to sleep on it & maybe start tomorrow.

Thanks again

RDV

[MarkB]

Thanks, Alf...
great info!!
Time to break out the breadboard.
"-)