Passive midrange "boost" question

[Esppse]

Hello,


OK I'm trying to build half of this, and I'm trying to figure out if I need the other half for the half that I want to work, to operate correctly.

This is a midrange cut/boost(actually cutting lows and highs)

http://s301.photobucket.com/user/Nathan_C/media/MidrangeToneControl.jpg.html?1276522003

I only want the side that boosts the midrange. Can I remove all the components on the left side, or do I need them in because they are still making contact with the center terminal, and that is what makes the low and high cut.

Thanks

[GibsonGM]

Not seeing any pic!  Photobucket tends to be a pain; don't know if that's the cause of this, but maybe.  Most people use other services like "Imgur".  If you can save the image and re-up it from one of them, that would probably help.

[Esppse]

Ah sorry! Here is a different picture.

http://www.projectguitar.com/forums/topic/14986-tone-and-this-midrange-mod/

[pinkjimiphoton]

the components on the LEFT side ARE the midrange part, bro.

you're gonna wanna leave the circuit as is if ya want it to work correctly.

personally, having tried it in the past, i'm not impressed with it enough to add to any of my guitars.

if ya want more midrange, convert to a hi pass/low pass arrangement.
if ya cut the highs and cut the lows, the mids will be more prominent.

i have this on virtually all my guitars, very versatile, and you can control fuzzes and some distortions drive levels with the bass control from the guitar as ya are playing it.

the mid pot was a bill lawrence invention. you can use an inductor, or a small transformer and just use the primary. cut the secondary off.

how do ya tell which is which? primary will have a higher resistance.

anyways... good luck bro!

[Mark Hammer]

It is a passive cut-only circuit, similar to one of the steps in a Varitone circuit.  That doesn't mean it isn't useful, but you won't be able to get any mid-boost with it, only less cut.

[pinkjimiphoton]

true, but to the unenlightened, anything that doesn't "cut" the signal COULD be seen as a "boost".... lol

sometimes its the only way ya can describe it to some folks...

well no, those controls work by CUTTING frequencies.....

so, when its on 10, then, it boosts, right???


errrrr.... yeah....

[Mark Hammer]

Of course we can take that even further with amp tone controls.  The classic Fender or Marshall stack only cuts.  There is NO boost whatsoever.  However, because they are designed to provide a midrange scoop, when one restores the treble or bass (i.e., inserts less cut), because there is little restoration of the mids, it can sound like treble or bass boost, even though it isn't.

But enough blathering...

The OP wants to know if the illustrated control requires both halves to work.  The answer is "No...in both directions".  Removing the cap+inductor on the one outside lug turns it into a standard guitar treble-cut.    Eliminating the cap shown on the right in the drawing, and using the cap+inductor on the left allows for cutting frequency content that fall above frequency X and below frequency Y.  If the frequencies are chosen right, that results in a variable mid-scoop.

If I'm not mistaken, the bi-directional control shown is often suggested for Strats.  Personally, if it were used for a guitar, I would suggest use of a linear Tone pot value 4x the usual (i.e., 1meg if "usual" was 250k).  Why?  Well, the midpoint would be assumed to be no cut of any kind.  At the midpoint, you have 500k on either side of the wiper.  But 500k in parallel with 500k = 250k.  So, even at the midpoint, one will have some bleed to ground unless the pot value is large enough to mimic having a single control be of similar value to a stock Strat Tone pot.  Use of a 500k pot is like having a pair of 250k pots in parallel, or top end bleeding out through 125k.

The cap and inductor values can be selected to provide mid-cuts in different ranges.  Indeed, the component values could be selected such that rotating in one direction cuts mids in this range, and rotating in the other cuts mids in that range.  However, what is shown is intended to provide a more traditional treble-cut in one direction, and midscoop in the other.

[Rob Strand]

if ya want more midrange, convert to a hi pass/low pass arrangement.

The G&L Basses actually used that config for many years,

https://www.bassesbyleo.com/gl_bbe_wiring_diagrams.html
https://www.bassesbyleo.com/paul/g&l_bbe_wiring_diagrams/basses/l1000_schem.jpg

Passive "boost" is achieved by reducing the level of where "flat" is.  So if you divide the signal down by a factor of 2 in the flat setting you have the option to boosting the bass/treble/mids by x2 (6dB.)   That's how the passive James Tone control works (sometimes people call it Baxandall); the flat position has an overall loss.

[Esppse]

Ah thanks for the clarification. Yeah I was wondering if one side could operate without the other half.

However I thought the side with the 1n(some shows 10n) supposed to reduce both highs and lows, leaving the midrange, and not just a normal high roll off.

Or does it only reduce both lows and highs while the opposite side with the inductor is still soldered on?

[pinkjimiphoton]

the side without the inductor is just a standard tone control from 10-5ish.
the extra resistor is there to modify the taper of that half of the pot travel. it will not cut any bass at all as shown, strictly a low pass  filter/treble cut.

the left side is a midrange cut only, tho as its turned down the right side is pretty much taken out of the equation.

no boosts. no bass cut.
if ya build just the one side, you'll get an odd sounding tone control that only works for half the rotation.

[Esppse]

Ah OK thank you, I thought the 1meg resistor was there for tonal purposes to shape the low end, my mistake.

So is it possible to make the right half remove both highs and lows? The complete opposite tone of the left direction. I would that require the addition of a secondary pot?

[Mark Hammer]

Capacitors allow frequency content above some value to pass unimpeded.  Inductors allow content below some frequency range to pass unimpeded.  When they are placed in series, and if their values are chosen appropriately, content above this value but below that value can pass unimpeded.  If the cap and inductor are part of a path to ground, they will bleed content between the upper and lower values to ground...as long as there is no large resistance between them and ground.

In the Electronic Projects for Musicians book, Craig Anderton has a "passive tone control" project, that puts an inductor/transformer and cap in series with a pot to scoop mids.  Because the transformer has a center tap, he uses a switch to select between two different inductance values, and a rotary to select between different cap values, to provide a variety of scoops.

I decided to go one step further, and wired up the rotary control to have one of the setps simply bypass the cap altogether (i.e., one of the "caps" is just a straight wire.  I wired up a 3-way toggle to select between the whole transformer, half the transformer, and bypassing the transformer (again, one of the positions is simply a straight-wire feed).  The additional options allow the circuit to function as a variable midscoop (cap + inductor), variable treble-cut (cap only), variable bass cut (inductor only), and volume control (no cap or inductor).

[pinkjimiphoton]

Ah OK thank you, I thought the 1meg resistor was there for tonal purposes to shape the low end, my mistake.

So is it possible to make the right half remove both highs and lows? The complete opposite tone of the left direction. I would that require the addition of a secondary pot?

i've been told no, but yeah, you probably could do it. a double gang pot. may need a triple gang pot.

ORRRRRRRRR.....

lets see... cap in parallel with variable resistance = hi pass filter
variable resistance in series to ground = low pass filter

why not combine the two into one half of the pot, and the mid control to the other?

i've done something similar in the past with both filters on one pot, and it DOES work, tho its kinda weird... it may be ok, or may not. try it and see if it works for ya.

but here ya go:




the .0022 cap in conjunction with the variable resistance of the 500k pot is a hi pass filter, as its turned down, it should reduce bass frequencies in a useful range for guitars... should, my phat pink ass, i know it does, as i wire these into every guitar i own

the .022 cap from wiper to ground is a low pass filter, a standard tone control that shelves off treble.

the two work at the same time? hmmm... maybe. half way down, the .0022 should be shorted out by the pot in theory, but in practice, no, there's always a bit of resistance, thats why pots are lossy unless designed to offer no load.

the mid control part would be from  5 to zero.  i don't know if the bass and treble cut will still have effect as you turn it below half. you should still cut treble. but the thing is, if ya cut treble, and cut bass, and cut midrange, well...

isn't it ultimately a volume control at that point?


you could try this, too.... i use it on some of my guitars with only one tone knob. beginning of the rotation cuts the bass, below half it cuts treble






neither is perfect, but if ya drive as much fuzz as i do, they can be real useful real quick.  i've been told they can't possibly work, but i disagree. 
a big muff tone control is basically lo and hi cut filters on one pot, too
you may need to add tapering resistors, etc to get it to work usefully.
generally, a 10% reduction in bass from a guitar is a LOT... so ya may wanna play with some resistors.

they're weird, but they work... well, the second one does, i don't see why the first shouldn't as well

[Esppse]

Wow so many wonderful tonal possibilities. I'll definitely try them out. I've done my own varitone too, a 12 position with switchable inductors. Volume drop is sometimes too much on the smaller caps, but I guess in front of a driven amp, youll hear it much clearer. And I thought I tried out all the volume pot mods already hah. Thanks a lot!

[pinkjimiphoton]

hahahah beware, no guarantee they are musical or useful mods.

i like some of them  with very heavy distortions and fuzzes very much. but the taper/sweep will be weird, and ya may get unexpected results.
thats the fun of doing this stuff.
sometimes crazy stuff does ridiculously cool things

mark's suggestions are probably more useful. i did try a variant of the tone control dealio but i think i tried to do it opposite of that, so the high pass was to the bottom and it was kinda weird, like a bizzarre volume control with tone control at the same time. almost like a broken wah when ya got a fuzzface going, or if ya try and convert a crybaby into a vol wah by lifting the cap... it is a volume AND tone kinda thing.
when you cut bass, you lose percieved volume. that can be a good thing.
google up joe gore's tonefiend site
and dig his thing about ptb, passive treble/bass
turning the bass down from the guitar can clear up tones
and give ya pockets
that you may not expect.
if ya lose a little volume? so what?
crank your amp up a little more. you'll cut better in a live mix environment, and won't be stomping all over yer bass player.
you can dial down the bass and suddenly hear your vocal monitors. its kinda cool


ymmv

check 'em out, and if ya think any of its cool, let us know!

peace

ps... weirdest trick i ever saw was the center tap of a humbucker, one of the old 3 wire ones, so you could
"split the coils"
the guy had wired up the center tap to the middle lug of his tone control
on an old epiphone coronet or crestwood or something like that
so when ya turned down the tone, it also cut the one coil progressively to ground while still cutting the treble with the other half of the pot. it was pretty hip, and actually quite toneful thru a raging stack of 70's earbleed.
the possibilities are still awaiting to be discovered... ya never know when something obvious and cool will just kinda happen in your travels.

oh yeah... on a strat if you're ever really bored, try jumping across the volume pot
with a HUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUGE
freakin' cap.... like ya would a treble bleed...

try like, .22 or something. maybe between .022 and .47,
big range, i know, but..
you can put it on a switch, and use it to bleed not just treble past the pot, but a good bit of the midrange... depending on the value cap, different amounts.
now, when the guitar is up all the way, the cap is effectively bypassed and the full <ha!> output of the guitar goes to the output.
but as ya turn it down,  as you go lower on the volume, it will get phatter, particularly with distortion, and with your tone control with it you can get some serious nasal honks and woman tones with it, and as ya turn it down still more, a nice fat sassy cleanish tone.
works with bucker or single coils.
i used to put that sucker on a switch, and then kick it in for a bit of a boost for choruses or whatever or if i needed a phatter tone when turned down comping, while someone is singing or whatever. works pretty good.
that with a treble bleed setup you can get a lot of good tones happening just off your volume knob.
add in your fav mods and make that sucker sound like ya want it to

[Esppse]

Alright I'll be sure to try them anyways, I love crazy fuzz tones so the wilder and rare sounding, the better!