Boss Metal Zone tone controls

[sfr]

Okay, for some reason after work (12 hour night shifts suck) today I ended up trying to learn Slayer riffs (I know, I know - it's a challenge, please don't pick on me - I was trying to play Stones and Hendrix yesterday if it makes you feel better) - mostly to play with my Boss Super Pitch Shifter in an attempt to emulate the two guitar harmonys.  Anyway, to get a workable tone I pulled out my old Boss Metal Zone, and after realizing I'm not really a metal head, (and the batteries on my practice walkman dying out) I started playing with the Metal Zone, and while I'm not a huge fan of the distortion sound, I was really digging the tone controls - it made the pedal a lot more versatile than it might otherwise be.  So I went hunting for the schematic, interested in the idea of splicing the tone controls (particularly the whole mid boost/cut and mid frequency knob idea) onto a distortion circuit I'm more into.  

I found a couple links on the schematics page here, and downloaded the two part .jpg set, and the .zip file, and compared the two and tried to figure things out.  

So if you download the .zip file - ( http://www.mif.pg.gda.pl/homepages/tom/files/MT2.zip ) and open it up, and look at the "mezon2.gif" file - that seems to be the tone control bits, right?  

So a few questions -

I assume the sort of sideways slashes (like coming out of the 2k2 resistors) are connections to ground?

That file has "1/2v+" connections - the other file (the two part .jpg one) has "4.5v" connections - I'm assuming the later is correct, and the first just means 1/2 of the voltage, not a half volt? And this voltage really just depends on the op-amps I use in the tone controls anyway, right?  

Looking a the "mezon2.gif" file inside of the .zip file again, if I wanted to try splicing this into another distortion circuit, I would do that towards the end of the circuit, and the signal would come "in" the point labelled "B" and "out" the point labelled "C"?  

Changing it up a bit, is this a good place to use some of those quad op-amps I have lying around, even though the original used duals?  

I think that's all I have to ask right now - I've never really hacked at anything quite this much before - I was thinking for now I'd try sticking this on the end of a dist+ type circuit, since that tends to be my favorite distortion lately, and I often find myself heavily EQing it when I run it into the computer, fooling around with mids and such, so I was thinking this sort of EQ might be fun.  Or it might not work at all.  I guess I'll see.   Any general pointers people have would be nice.

[smoguzbenjamin]

B looks like in and C looks like out

Ya sure you could use a quad opamp for this... need a dual ganged pot though for that freq. control.

I have a metalzone and I like it!

[sfr]

questions about powering the whole thing . . .

(looking at the "mezon2.gif" file in the .zip file again)

So if I feed my 4.5V into the circuit at the points listed (through the 100k resistor into the non-inverting input on one op-amp, and into third lug of the the volume pot) Do I still need to feed voltage (the full amount?) into the Vcc of the IC(s)?  I guess this seems like a stupid question, I'm still learning basic design things - I understand building and repairing, but designing is beyond me a lot of the time.

[Joep]

Yes, you need both, bias and supply voltage are separate things.

[Mike Burgundy]

I assume the sort of sideways slashes (like coming out of the 2k2 resistors) are connections to ground?

Yes

That file has "1/2v+" connections - the other file (the two part .jpg one) has "4.5v" connections - I'm assuming the later is correct, and the first just means 1/2 of the voltage, not a half volt? And this voltage really just depends on the op-amps I use in the tone controls anyway, right?

Opamps (most, anyway) want a bipolar supply. This means they want +xxV, ground, and -xxV with xx as a certain voltage. One battery only supplies a monopolar supply (+9V/ground) so there's a little trick in there: with a resistor devider you cut the supply voltage exactly in half (ususally called Vr (for ref), 1/2V, or whatever. When using a 9V battery Vr will be 4.5V, so yes, it's the same.
The trick is now that we "tell" the opamp that 4.5V is actually ground, so the opamp thinks it has a bipolar supply of + and - 4.5V. It operates around it's own local "ground" which is really located at 4.5V. This is why we need caps to isolate opamp stages (to prevent DC getting to other electronics such as pots - scratchscratch) and we need to float at least the + input of an opamp at 4.5V. This is what the bottom left 1/2V+ connection does for the adjacent opamp. Others aren't floated and won't work properly, so you need to hook them up to 4.5V through something like a 100k resistor, unless the + is hooked up to the output of another opamp without caps in between. The volume pot should be connected to ground in this configuration (in the original this is the bias for the next stage), and before the 100k to 4.5V on the input you should put a series cap to block DC

Looking a the "mezon2.gif" file inside of the .zip file again, if I wanted to try splicing this into another distortion circuit, I would do that towards the end of the circuit, and the signal would come "in" the point labelled "B" and "out" the point labelled "C"?

B is in, C is out. An EQ like this will have most sonic impact after distortion, yes.
Quad opamps will do just fine, although I don't think you're making your life any easier layout-wise.

So if I feed my 4.5V into the circuit at the points listed (through the 100k resistor into the non-inverting input on one op-amp, and into third lug of the the volume pot) Do I still need to feed voltage (the full amount?) into the Vcc of the IC(s)?

See above about the volume pot, etc. You do need to supply the circuit with regular power as well. The opamp thinks you feed it two batteries (+4.5V and -4.5V), so if you don't hook up 9V, it will think one of the batteries is not there and won't work properly.
hih

[sfr]

Thanks Mike, and everyone.

Yeah, I layed out all the components in that section of schematic, and the quad op-amps are a nightmare.  The layout was actually bigger . . . I don't know how I ended up with these things, but I'd sure as heck like to get rid of them sometime.  Maybe next time.

I really appreciate yr post Mike, it cleared up a lot of things I was sketchy at best on - I think I actually understand a lot of things I was just peripherally aware of before.  I searched the usual places, and I'm know I'd seen the info before - but I wasn't exactly sure what I was looking for!  Terminology and stuff.  

This is why I love this forum.
 

[Mike Burgundy]

If you want I could redraw that schem as a working stand-alone circuit tonight. If you've already got it sorted I'll leave that to you though
This is a good one to actually stick in a box all by itself!
I've been working on a true parametric EQ already, but this one is very cool too.

[sfr]

Yea, I was starting to think the same thing - throw it in it's own box and you could toss it after anything.  My plan was just to make it on it's own board and play around with it, and if it worked out okay, toss it in the same box as whatever circuit it got attached too.  

If you get the feeling to draw up a standalone schematic, then hey, that's cool - I think I'm sorted and I'm still going to draw one up myself- I want to make sure I understand this - I'm realizing I have wierd random holes in my knowledge, so something like this is good to make me fill in one of those holes!  

thanks again.

[smoguzbenjamin]

Mike, draw this one up for me, please! Looks like something fun to play with.

Alsjeblieft?

[Mike Burgundy]

We all have holes, some larger, some smaller. You keep filling them as you go along
Check this message later on (in an hour or three), I'll whip something up after dinner.

Edit:
Smoguz', I whipped something up:
http://users.balpol.tudelft.nl/~Burgundy/bin/parametricmetalzone.gif
Untested and unsimmed, but it should work. Don't see why not.
I did include an extra buffer to keep from interfering with tone control fuctionality.

[smoguzbenjamin]

Cheers mate

[rx5]

thanks for the Eq man....

maybe gonna put it AFTER my Tone Bender...... that would really sound VERY VERY NICE !?!?! ROCK ON !!! :twisted:  :twisted:  :lol:


-Ralph

[smoguzbenjamin]

Wow... That might just go in the mixer design... I have a mini mixer perf'ed but not wired so I might just add this to do some pre-effects toneshaping

Thanks Mike!

[Joep]

Or combine it with an Obsidian, that will be also really cool I think....

Joep