Mid Booster

[Venusblue]

Hey, A mid booster isn't something you see everyday, but i'm totally in love with my mids.

I wanted to build a mid booster into one of my pedals, but i'm having a hard time finding a schematic for one and i'm a bit too much of a noob to build my own. The one I found was REALLY easy but used weird values I can't find anywhere. The schematics are... Right here


I was just using the mid boosting half. I can't find 500pf and 15(nano fared? It just says "n") I'm wondering if I can just get a simple treble booster and change the values of some of the resistor. I would like to be able to be able to boost or scoop the mids, for those Big Muff kinda tones or something a bit fuller.

Anyone have any ideas?

[JKowalski]

The "second half" is a tone control that doesn't necessarily "boost" the mids, but just attenuate everything BUT the mids. The LBP amplifies everything, so that the everything but becomes unity and the mids becomes amplified. \

XXXn means nanofarad, yes.

Look into active tone controls for a one-op amp stage that will boost mids and leave everything else unity. Thats all I can say right now cause I got to run off to school!

[Mark Hammer]

This Craig Anderton circuit does a nice job and can be insert in many other pedals.  Note that it can be easily designed to provide boost wherever you want it (i.e., the band of your choice).

[Venusblue]

This Craig Anderton circuit does a nice job and can be insert in many other pedals.  Note that it can be easily designed to provide boost wherever you want it (i.e., the band of your choice).

Hmm that one looks pretty promising. It takes 12v though? Will that mess up my circuit that's meant for 9v? Will it give me monstrous amounts of fuzz? Because that's totally cool if it does, lol.

What is the midrange for guitar? I don't really know the hz, but i'm assuming it's around 1khz from the notes on the schematic. I always thought it was a bit lower then that, but i don't know much about circuits I guess.

[Mark Hammer]

Actually, it can be easily rigged to run off a single 9V battery.

Here's an example of the circuit inserted into a modified Anderton Tube Sound Fuzz:

You can see the only real difference is that the on-off switch is connected to Vref (Vb) rather than ground.  Note that the Vref is provided via the 330k resistor on the input of the earlier stage.  IN fact, if you built a circuit that included everything up to the 10k "Drive" pot, that would be a midrange booster.  Since the first stage shown has a gain of 48, you probably want to reduce that.  Drop R3 down to 10k, make R4 3k3 or 3k9, and you're good to go.  The values shown in the schematic get you three sorts of midrange resonant boosts.  Use the values shwon in the earlier Anderton schematic I showed to give you some guidance on what values you may want for the boosts you are interested in.  They can be achieved through toggles or a rotary switch.

[Venusblue]

Hmm it's a little complex I think, i'm not very good at all this stuff, but this will be an interesting build, and most of the parts are pretty common.  I was also thinking of putting in a switch to change it from a presence to "beefy" or something, It would just set it for the high midrange or low midrange.

Man, that last schematic is a bit confusing, trying to figure out what everything is doing. I think i'll go with this design though, I like that it has a more rounded midrange bump, instead of the more jagged bump that the first would produce. I think a rotary switch might be a little bit too much, but I think wiring up a toggle might be an interesting idea.

[gigimarga]

A famous mid-boost circuit is the one which was used in Eric Clapton's guitar: http://www.blueguitar.org/new/schem/_gtr/ec_schem_fact.jpg.

More informations you can find here: http://www.diystompboxes.com/smfforum/index.php?topic=33315.0

I've built it sometime ago, but it didn't impressed me too much.

You can find my layout at http://www.aronnelson.com/DIYFiles/up/clapton_mid_boost_layout.pdf and my PNP at http://www.aronnelson.com/DIYFiles/up/clapton_mid_boost_pnp.pdf.

I omitted the jacks and the pots, but you can find their connections using the schematic.

[Mark Hammer]

I'll try and post the original Anderton schematic later this evening (what Jack Orman has posted is incomplete).  It's actually a pretty simple circuit, and no more complicated than what you presented in your original LPB+tone-control drawing.  The advantage is that it is essentially flat outside the region of the resonant boost.  It only really starts to get complicated if you decide to provide more than one possible boost frequency.

[Venusblue]

I'll try and post the original Anderton schematic later this evening (what Jack Orman has posted is incomplete).  It's actually a pretty simple circuit, and no more complicated than what you presented in your original LPB+tone-control drawing.  The advantage is that it is essentially flat outside the region of the resonant boost.  It only really starts to get complicated if you decide to provide more than one possible boost frequency.

That would be great, thank you.

Do you think it would affect the tone too adversely if I only boosted one frequency? I was thinking of having a three way toggle, where you could select high mids, mids or low mids. That way you can select high mids for a lead tone to cut through the mix, or mid/low mid for a thicker tone. Would that be too hard, or would it be better to have them all on at the same time?

[Mark Hammer]

Turns out I don"t have to post anything.  Paul Marossy was kind enough to do so several years ago...and with a PCB layout!

http://www.diyguitarist.com/PDF_Files/FreqBooster.pdf

[Venusblue]

Turns out I don"t have to post anything.  Paul Marossy was kind enough to do so several years ago...and with a PCB layout!

http://www.diyguitarist.com/PDF_Files/FreqBooster.pdf

Hmm this one looks a little complex too, and it doesn't boost several frequencies. Would that sound bad compared to several of them?

Also are the two op-amps needed, or is just the single fine? Hmm... I'm just a bit worried because i'm not very good and this seems like a bit of a hard build.

[liquids]

I was just using the mid boosting half. I can't find 500pf and 15(nano fared? It just says "n") I'm wondering if I can just get a simple treble booster and change the values of some of the resistor. I would like to be able to be able to boost or scoop the mids, for those Big Muff kinda tones or something a bit fuller.

Anyone have any ideas?

I remember this from another thread of yours...about gain pots and mid boost.

Down to brass tacks, almost none of the values in that schematic you link are common, and in the tone control, the major ones are all unusual. 
Now really, in general, you are 'best' to sub the closest values you have so you can simply hear the circuit for starters.    If so you might hear how odd this circuit is likely to be (very strange EQ curves) ..and that the stock values could probably use major tweaking...though who knows, you might like it(!)...but either way, you could go from there.   Since it's simple, it's a good place for you to start.  It would get you to the bread board and auditioning with your ears, rather than theory of how one circuit sounds vs another....

And note that theirs nothing to suggest that those stock values in the tone control make any sense.  There's also many other values swaps that could yield similar or the same results if combined correctly.  But I'll break it down into more common values for now...so, going with stock for the moment....

15n can be yielded by a common 10n capacitor ('103') and 5n/4.7n ('472') connected in series, which are common values.

500pf is not going to be that much different than the common 470pf or 560pf.  Simple substitution.  Or just add a 22pf or 33pf cap in series with the 470pf if you are loosing sleep over the differences.

11M is another wacky value, but easily obtained with a simple, common 10M.  Or, put the 10M in series with a 1M if you must have 11M. 

25K is not super common...22k would do just fine.  If you must get closer, put a 22k in series with a 3.3k.

That being said, in an ideal-impedance  world (of which this particular boost circuit is not), 10M/470pf is  a low pass filter (highs are cut the most, lows are cut the least) that is going to have a frequency roll off point that starts below the guitars frequency range - ~ 29hz, cut starting around there.   That's hardly a treble cut, it's an everything cut.... 

The other side, 15n/25k, is a high pass (low cut) filter that starts to cut ~440 hz, and cut the bass more as you go down from there. Note that 440hz is the fundamental of the note you play on your guitars high E string at the 5th fret, if I'm not mistaken. 

Not sure what you are after, but try it and listen.  Likewise,   you could replacing the 15n with 10n and 25k with 100k might give you a subtle low cut, and going with the 470pf and 100k would give you a subtle treble cut, yielding a big, more general mid boost to compare it to.  You could tweak from there by ear and learn as you go...

I'd also move that 100k pot to the end of the circuit rather than between the transistor and the 'tone stack.'  It's going to interact with the tone stack a bit where it is right now. 

We've all been 'noobs.'  But even beginners can experiment on a breadboard and hear for themselves...and it's rather educational, and fun at that!  It's my idea of a good time.   And while you expiriment, help yourself with a few resources....this site will help you calculate frequencies as you learn more about tone stacks, etc: http://www.muzique.com/schem/filter.htm
Moreso, surf the net for the Duncan Tone Stack Calculator so you can experiment for yourself similarly but with a visual frequency curve.   

Also, search here on the forum for variations or talk about the BMP /Big Muff Pi tone control...that's what your working with here, on base level, and they're used quite a bit around here in infinite variations to try...