With this mod:
(http://www.jpbourgeois.org/guitar/images/midboost.gif)
If I wanted to do this without a pot and just a switch, would I need to increase the value of the 1 meg resistor??
You don't have to change a thing.
But...having never seen/tried/read about this circuit I got all curio-spicious, and decided to focus on "Pickup drives Inductor?" as an aside to changing the 1meg, which would change the ratio between the R/C, the "C" value being quite high for a ground shunted capacitor for guitar pickup. Or removing the pot as a starting point.
I would say a higher resistance in parallel [what the pot is doing when turned >right] with the .02 cap would tend to let more signal [HF's in particular] through.
By removing the pot, ~500k is removed from between the left and right shunt rolloff circuits [inductor>R/cap on the left, R/C on the right].
Maybe start by putting a 470k [or less] at the pot position to see what CCW and CW would have sounded like. Then parallel smaller resistor to reduce the R where the pots outside lugs were, and add a resistor to form a fixed divider that'd be like some middle pot settings...iow diddle with resistors to form something R or R-divider, like what'd be like what the 500k pot shown would do.
Starting off as shown or with any pot or some big resistorances [maybe form a 'switch pot' with a string of "add and divide" by choosing tap point] resistors there] between the I>R/C and R/C.
Is this a "boost" at all?
Turn pot to 0.02u||1Meg side. You have 0.02u loading the pickup. This wipes highs off, may exagerate pickup top-resonance. Network impedance never gets close to 1Meg, the resistor seems unnecessary.
Turn pot to 0.04u+L side. The L-C network goes to a low impedance at one frequency. This wipes out a band of middle frequencies, a mid-dip. For a 0.8H inductor, 880Hz will be very weak. Inductor Q is perhaps 5, reactance about 4K, dip impedance about 800 ohms. Against the ~~5K+5H pickup impedance you get a fairly narrow dip, probably leaving everything below 400Hz or above 1600Hz nearly full strength.
And it sure looks like a commercial mid-dip product discussed here recently. Their snazzy network analyzer plot resembles my one-thumb analysis.
me> Is this a "boost" at all? ... 0.02u loading the pickup. This wipes highs off, may exaggerate pickup top-resonance.
After some more study:
Actually the 0.02u across the pickup will give significant pickup top-resonance bump, about 7dB boost near 500Hz, a real "mid boost". It also clobbers everything over 800Hz.
This very narrow spectrum -may- be useful for fuzzing-up. Losing the highs reduces IM hash and spectral clutter.
The 1meg resistor still seems unnecessary. So the project is a switch and a cap.
So it really DOES boost mids? I thought it just cut lows and highs leaving only mids.
The problem is, I'd actually already stuck it in a 45 dollar guitar I bought at walmart. I used a center off SPDT switch. On one setting is just the inductor and resistor+cap to ground and on the other is a 1M resistor andthe .02 cap in parallel to ground. I didn't realize till after that that I was doing was different from what the circuit with the pot does.
I like the mid "boost". It cuts highs, but I like the sound of it. I have it in a cheap squire strat. Gets QOTSA sounding.
is what I did doing what the circuit with the pot is doing?
> I like the mid "boost". .... I like the sound of it.
So be happy. Nothing wrong.
looks interesting !
I'm never really happy with the "classic" tone control on guitars (I never use it , like a lot of people I guess).
That thing seems simple, and can be remove easily . Just find an inductor to do it,
what value for it by the way ?
Look at this recent thread check the links
http://www.diystompboxes.com/smfforum/index.php?topic=84527.20
I wonder how the inductor or transformer from a CFL might do for one of these...
The inductor is only needed for the mid scoop. The mid boost doesn't need it if I'm not mistaken....but I could be.
PRR, I didn't think there was something wrong with the circuit. I'km not trying to change it I'm just trying to do it without a pot. I can't fit another pot in the guitar Im doing this in. I wanna do it with an SPDT switch. A center off one, so the center will be untouched.
Quote from: El Heisenberg on May 24, 2010, 06:13:55 PM
The inductor is only needed for the mid scoop. The mid boost doesn't need it if I'm not mistaken....but I could be.
Not sure what exactly what you are referring to, but you do need the inductor for the mid boost to work. It needs the resonance created by the inductor to do its thing. Otherwise, it's just a variation on the usual capacitor tone control.
The usual capacitor tone control does boost mids because it make a LRC resonant filter with the pickup's inductance and resistance that cuts highs, has a resonant boost in the mids, and cuts bass. The inductor makes it act like a varitone, scooping mids resonantly.
Quote from: CynicalMan on May 24, 2010, 09:06:28 PM
The usual capacitor tone control does boost mids because it make a LRC resonant filter with the pickup's inductance and resistance that cuts highs, has a resonant boost in the mids, and cuts bass. The inductor makes it act like a varitone, scooping mids resonantly.
I know it's an LRC filter, but I don't think of a standard tone control as a mid boost, I see it more as a high cut control.
I always thought that these passive inductor "mid boosts" used the inductor to boost the mids, and it worked by creating more resonance. I haven't tried messing with this idea, but I guess I got the idea that it was a mid-boost from what this guy said in this thread: http://www.diystompboxes.com/smfforum/index.php?topic=42087.0 - but it's not really?
So can you explain how you "resonantly" scoop the mids? That doesn't make any sense to me. Do you mean that it has some resonant frequency above the midrange frequency so that it gives the effect of scooping the mids? I know the wah circuit is not a passive circuit, but the inductor is
the component that makes it a resonant circuit. And the wah patent documents directly state that. And inductor based graphic EQs use various size inductors for each frequency band. So I am confused on how you can use an inductor to cut a frequency in a guitar... I mean normally you dump it thru a variable resistor and a cap to ground. Then the inductor shouldn't even be in the picture. Am I missing something?
What i've been told about the mid scoop circuit is that it cuts highs, then the inductor puts them back. I've also been told the inductor doesn't do anything with the mid boost function. I mean, the inductor is bypassed when in mid boost mode, isn't it?
So it's like the Villex boost ? ( http://www.villex.com/prtb.html ) ...
And it works ?
Simon
Quote from: Paul Marossy on May 24, 2010, 10:15:31 PM
So can you explain how you "resonantly" scoop the mids? That doesn't make any sense to me. Do you mean that it has some resonant frequency above the midrange frequency so that it gives the effect of scooping the mids? I know the wah circuit is not a passive circuit, but the inductor is the component that makes it a resonant circuit. And the wah patent documents directly state that. And inductor based graphic EQs use various size inductors for each frequency band. So I am confused on how you can use an inductor to cut a frequency in a guitar... I mean normally you dump it thru a variable resistor and a cap to ground. Then the inductor shouldn't even be in the picture. Am I missing something?
Check out http://en.wikipedia.org/wiki/RLC_circuit#Filters for more equations than you need. This filter is similar to Fig. 13 on that site. Anyway, a simulation is worth a thousand words, So:
(http://sites.google.com/site/distorque/home/projects/pictures/bandstop.PNG)
This is the inductor circuit with a voltage source and 10k ohms in series before the filter. For this sim and the one below I assumed the inductor was 1H
(http://sites.google.com/site/distorque/home/projects/pictures/scoop-boost.PNG)
This is a humbucker model run through both sides of the tone control compared to a unloaded humbucker. V(scoop) is the inductor side and V(boost) is the inductorless side. For V(scoop) there is a mid scoop, but also an upper resonant boost because of the pickup having inductance. The mid boost boosts low mids 4 dB but it would be pretty inaudible compared to the treble cut.
The inductor filter is resonant because the inductor and capacitor have a resonant frequency where, in series, they are at their minimum total impedance. This comes up as a cut because the low impedance shunts the signal at the resonant frequency. I'm afraid I can't give you more of the underlying reasons for this, but I'm sure a few minutes googling rlc band stop filter would turn up some results
Huh, very interesting. Thanks for explaining that.
El Heisenberg, why not using a trimer instead of the pot (if you don't want put it directely on guitar) ?
CynicalMan , thanks for the simulation, it's really clearer than long explanation ! I keep that circuit in my notebook, that could be a cool thing to add in my guitar project !
Otherwise, a french luthier , put a kind of bandpass filter in one of guitars, you can move the frequency with a pot installed on the top of the guitar's body. (That maybe not the only one who made that but it's the one I remember (there's a video on youtube about that by the way)
I didnt think the pot was needed until now. I still havent gotten an answer if it is or not. It seems like a waste of a trimmer if im using an SPDT switch and planning on using the effect on full all the time. Why not juts fixed resistors?
Ever check out Craig Anderton's "Passive Tone Control"? It's a very similar passive LCR filter.
http://i86.photobucket.com/albums/k99/jprak1/Passivetone.jpg (http://i86.photobucket.com/albums/k99/jprak1/Passivetone.jpg)
Beats me if you can still get the RS 273-1378 inductor / transformer, but it's spec'ed at 88-100 uH.
The original schematic (from the Ele. Proj. for Musicians book) doesn't have the POT... And some of the caps are different values.
"On full" it is really just a cap. The pot is there to get "less". The fixed resistors don't seem to do a whole lot; they may be for mechanical support (some cap leads won't reach?).
It does not sound like just a cap...i swear to god, try it.
(http://i86.photobucket.com/albums/k99/jprak1/Passivetone.jpg)
This is alot like the varitone control. I put that in my guitar last year. It doesn't have the 50k depth pot, nor the switch to change the inductor lead. It doesn't have the 47k resistor either. Cap values mightbe different but they look the same.
I have craig andertons "electronic projects for guitar" book and I never saw that in there.
Quote from: gmoon on May 26, 2010, 04:51:46 PM
Beats me if you can still get the RS 273-1378 inductor / transformer, but it's spec'ed at 88-100 uH.
http://www.mouser.com/ProductDetail/Xicon/42TM019-RC/?qs=LQJGOuQCHKQk%2faBX9yNCGw%3d%3d
This is my vari-tone control. It's in my rickenbacker 330 COPY. It's got humbuckers. The first setting doesn't do much anything. Cuts out some treble buzz maybe. I should change it. Also, my inductor is different.
(http://i633.photobucket.com/albums/uu56/el_heisenberg/Passivetone.jpg?t=1275006114)
craig andertons:
(http://i86.photobucket.com/albums/k99/jprak1/Passivetone.jpg)
What does the 47k resistor do? I'd try this in my guitar but it's already equiped with 4 push/pull pots and the rotary.
I never tried that circuit, but the Anderton book had one of those "flex" demo records and I recall being impressed with the sound--for a passive filter (OK, I bought my copy 30+ yrs ago...) That version is simpler, but I found this: http://mia-amps.com/images/varitone.png (http://mia-amps.com/images/varitone.png) , which is apparently from the same book, but must be a later printing. Somewhat different cap values, but otherwise the same as that other schematic...
Re: the 47K R -- isn't that combination of RLC a pretty standard band-stop filter?
While rare, there must have been several guitars that had some resonant filters standard. In fact, this morning I just recalled that my oddball Norma "Barney Kessel" has an onboard inductor.
(http://www.instructables.com/files/deriv/FI0/PKRD/G9NGTWLW/FI0PKRDG9NGTWLW.MEDIUM.jpg)
The guitar uses a LMH (Low, Medium, High) rotary switch. Never "reverse engineered" it, though. There may be some active resonance in "High"; in the other settings, it's more like a low-pass filter.
Quote from: gmoon on May 28, 2010, 09:00:19 AM
I never tried that circuit, but the Anderton book had one of those "flex" demo records and I recall being impressed with the sound--for a passive filter (OK, I bought my copy 30+ yrs ago...) That version is simpler, but I found this: http://mia-amps.com/images/varitone.png (http://mia-amps.com/images/varitone.png) , which is apparently from the same book, but must be a later printing. Somewhat different cap values, but otherwise the same as that other schematic...
I ought to try something like that ciruit you linked just for kicks.
Quote from: gmoon on May 28, 2010, 09:00:19 AM
While rare, there must have been several guitars that had some resonant filters standard. In fact, this morning I just recalled that my oddball Norma "Barney Kessel" has an onboard inductor.
I seem to remember that a specific Gibson electric had one in it. The Blueshawk, IIRC. I wonder why it never caught on in a wider scale? I'm guessing that people didn't like it that much and/or they didn't want to spend $20 more on the manufacturing costs per guitar.
I think the varitone is a popular circuit for hollow body guitars. BB king has em. He's always messing with it. So I put it in my rickenbacker 330 copy I had. It's such a weird guitar. A really thin and narrow neck with a zero fret. And it's hollow instead of semi-hollow. With DiMarzio humbucker pick-ups. It was made by these guys that made Gibson copys mostly.
The vari-tone works great. But I'm gunna switch up the cap values. I started this thread for work on a new guitar and now I'm messing with a different guitar.
Isn't this the same as the varitone posted earlier? I don't see a difference?
(http://mia-amps.com/images/varitone.png)
Same cap values
@El Heisenberg
Sorry--I'm just trying to identify if that last schematic is actually from C. Anderton, rather than discuss the merits of each. None of these match the Anderton circuit in my book (close, but not exact to say they are Craig's for certain.)
Re: the 47K resistor--it does reverse the operation of the filter, from mid boost to a notch (also attenuates the signal somewhat overall, 9 or 10dB.) So it's definitely different. The resister value also has an effect on the Q--the smaller the value, the narrower the notch.
Here's some Gibson Varitone schematics, which are somewhat different from all the others...
http://www.flatearthguitars.com/files/Gibson_Varitones.jpg (http://www.flatearthguitars.com/files/Gibson_Varitones.jpg)
Paul, I'd like to try it on something with humbuckers...
Quote from: gmoon on May 28, 2010, 10:57:46 PM
Paul, I'd like to try it on something with humbuckers...
Yeah, same here.
Yeah, I was calling it varitone, but it's not.
Maybe i'll record clips or something. But I want to get another inductor and try it with a 50k push/pull pot, exactly like this one. I'd have to get rid of something else on this guitar tho.
You say the schem of the circuit I'm using, and the one with the 47k resistor will sound really different???
Quote from: El Heisenberg on May 29, 2010, 06:07:50 AM
You say the schem of the circuit I'm using, and the one with the 47k resistor will sound really different???
Hmmm. Playing with LTSpice, I thought so. Until I set the series resistance of the AC signal source to a non-zero value (something like 5K, to match a pickup.) Then they both behave as notch filters. Anderton's book certain describes it as a notch filter.
The 47K broadens the notch, so it resonates over a wider freq. range.
But if you're getting a midboost rather than a cut, maybe one or more parameters of the sim inductor (or signal) are "ideal," and the sim is not behaving in a real-world way...
Edit:
Testing your original varitone, adding a coupling cap after the signal source yields a similar sim graph as CynicalMan's notch, followed by boost (the blue "pen"... If the series resistance is "default") YMMV for sims; the cap is probably not necessary...
Oh, gmoon, the mid "boost" we were talking about is a differetnt circuit. I don't remember somehow we started talking about rotary controlled tone switches.
Hey, what does switching to the middle lead of the inductor sound like?
> set the series resistance of the AC signal source to a non-zero value (something like 5K
No, a pickup has a strong inductive component.
5K resistance plus 5H inductance will show the general effect of external loads.
Stuff that throws a capacitance directly on the pickup, that inductance really matters. What "should" be a low-pass becomes a ringy lo-pass with a substantial boost before the droop.
And dropping-in that 47K between the pickup and the cap spoils the ringiness, simpler low-pass with little or no bump.
@El Heisenberg
Yeah, just try to help answer the "what does the 47K R do?" question... I probably sent this OT. Still, they are all simple LCR filters...
Quote from: PRR on May 30, 2010, 01:55:04 AM
> set the series resistance of the AC signal source to a non-zero value (something like 5K
No, a pickup has a strong inductive component.
5K resistance plus 5H inductance will show the general effect of external loads.
Stuff that throws a capacitance directly on the pickup, that inductance really matters. What "should" be a low-pass becomes a ringy lo-pass with a substantial boost before the droop.
And dropping-in that 47K between the pickup and the cap spoils the ringiness, simpler low-pass with little or no bump.
Right, I realize that a simple AC source in SPICE does a lousy job simulating a pickup.
Would an inductor (with a set DC resistance) in series with the AC source be a better sim? Or an inductor with a series resistor, perhaps?
Quote from: gmoon on May 30, 2010, 09:10:03 AM
Right, I realize that a simple AC source in SPICE does a lousy job simulating a pickup.
Would an inductor (with a set DC resistance) in series with the AC source be a better sim? Or an inductor with a series resistor, perhaps?
sites.google.com/site/distorque/home/articles/spice-humbucker-model (http://sites.google.com/site/distorque/home/articles/spice-humbucker-model)
I use a inductor, a series resistor, a cable capacitance in parallel, and volume and tone controls in parallel.
Quote from: CynicalMan on May 30, 2010, 09:22:15 AM
sites.google.com/site/distorque/home/articles/spice-humbucker-model (http://sites.google.com/site/distorque/home/articles/spice-humbucker-model)
I use a inductor, a series resistor, a cable capacitance in parallel, and volume and tone controls in parallel.
Good stuff, thanks. :)
> Would an inductor (with a set DC resistance) in series with the AC source be a better sim? Or an inductor with a series resistor, perhaps?
5K resistance plus 5H inductance will show the general effect of external loads.
Would putting a 150k or 220k resistor in parallel with one of the caps, say the .033 in my rotary tone control, I should get some lows back in that setting right?
Quote from: PRR on May 30, 2010, 08:19:02 PM
5K resistance plus 5H inductance will show the general effect of external loads.
Good to know--thanks.
I now return you to your regularly scheduled (original) post...
(http://www.jpbourgeois.org/guitar/images/midboost.gif)
So the circuit above, with the pot turned all the way clockwise in "midboost" mode looks like figure 1. here below, correct?
(http://i633.photobucket.com/albums/uu56/el_heisenberg/midtone.gif)
Or is it just the figure 2?? The 2nd circuit is what I put in the guitar. It doesn't sound like the circuit with the pot in my strat. The mid boost doesn't sound like it should at all, and the mid scoop doesn't have as many highs. It's doing what it should tho. I can't remember what cap I used...
Because I'm trying to have the two tone options in a guitar with one DPDT center-off switch.
?
Wired like the schematic, looks like a hybrid filter you got there...a combination of band-pass and band-stop filters. The two filters you reference interact into one; there's no isolation between them. There's an LC series shunt, and then a cap forming a LC parallel shunt. Plus the pickup inductance thrown in for good measure...
I think you'll get a freq response like the blue graph on cynicalman's post--a peak - notch - peak. The slope up to the initial peak I'm seeing is probably caused by the pickup sim. With this simple circuit the order (notch-peak) will always be the same. I'll let an EE or a physicist explain why...
Mixing them passively with the 500K POT does isolate the filters, but not in a helpful way, I think. You'll never get the same resonance as the original, just a modified low-pass. Probably giving you the worst of both worlds...
Use the circuit as drawn. Substitute a 1K (or 5K) POT for the 500K R. With the POT much above 1K, the second peak disappears and you'll get a low-pass filter (first peak - loooong notch.) The POT effectively takes the series LC out of the circuit (removes the inductor.)
Have you tried simulating this yourself? (in LTspice, etc.) It's worth it.
BTW, did you ever mention value of the inductor you're using?
I don't have any programs like spice or anything. This computer isn't really good for much. 2000 laptop. So I just use it to browse web pages....
The inductor was marked TL021.
gmoon, im not very clear on what you're saying. But I don't really wanna put a pot in. I can't fit another pot in the conrtol cavity. This is done with a center-off DPDT switch. One setting is the mid scoop (parallel cap and 220k resistor in series through the inductor to ground), the other setting is set so it's like the schematic I drew in figure 1. Center position is open. But is I were to play with the value of the 500k resistor it would do what? More highs? Cos doesn't the inductor add the highs back in after everything is cut?
Apparently, that transformer has ~1.5H inductance. I'll plug that in...
If I simulate that circuit, but replace a 100Meg R (functionally near open circuit) for the 500K R, there's almost no difference in the frequency response. I.E., 500K is way too much resistance to allow the inductive portion to ever come into play.
Notice how the other (Anderton?) filter uses a 20K "depth" POT? Even that's overkill.
Don't add another POT. Replace the 500K POT with a 10K POT (10K seems to work better with 1.5 Henries than the 5K I mentioned before.)
1 ohm:
(There's a real honest-to-God boost here @~1.25KHz. But it would be greater with other, simpler filter circuits. No matter.)
(http://www.instructables.com/files/deriv/FMC/YPSE/G9ZE9BIX/FMCYPSEG9ZE9BIX.LARGE.jpg)
2K:
(http://www.instructables.com/files/deriv/F2G/W14V/G9ZE9BIW/F2GW14VG9ZE9BIW.LARGE.jpg)
10K:
(http://www.instructables.com/files/deriv/F04/0R5B/G9ZE9BIV/F040R5BG9ZE9BIV.LARGE.jpg)
See the next graph? That's the one with the 500K. The series LC filter basically isn't present.
Not significantly different than the 10K graph, other than shifting the initial corner frequency, maybe. And lifting the signal a bit closer to unity.
(http://www.instructables.com/files/deriv/FFH/YXAA/G9ZE9BIR/FFHYXAAG9ZE9BIR.LARGE.jpg)
Your current setup below-- you've got the POT wired as a mixer between the two filters.
With the inductive half "full ON", and the RC half mostly isolated, here's the Freq response. I don't think it's anywhere near as interesting as the original circuit with the 500K removed, or reduced... (first two graphs). There's no secondary "spike", and the higher freq response just tables at -25dB.
With the POT turned the other way, the graph looks like the graph above this one. You're "mixing" the filters alright (introducing the notch), but not very effectively.
(http://www.instructables.com/files/deriv/FB1/HH6T/G9NHHKB0/FB1HH6TG9NHHKB0.LARGE.jpg)
Whew. That was epic capture/copy/pasting. Sorry.
Thanks for the explanation. But I'm not actually using a pot at all. I'm only using fixed resistors and a center-off DPDT switch to do this. I want both settings on full. Full mid scoop, and full mid boost.
I already have the circuit with the 500k control pot in a squire strat. I like the mid boost. But not the function of the control. I have the mid scoop half of the circuit in my rickenbacker copy. It sounds great. Or sounded great, I just took it out since the vari-tone gets me almost the same tones.
What would happen if I used two of these inductors. In series or parallell?
Anyway i bought a 40 dollar guitar at wal mart, added a neck humbucker pick-up since it only had a crappy humbucker at the bridge. I put an electra distortion in it and am trying to get this three way tone switch worked out. The settings don't sound like they do in the other guitars. Maybe it's the guitar. The bridge pickup is really dark and boomy.
EDIT: I just replaced the 500k fixed resistor with a 2k2 resistor. Now both scoop and boost setting sound sorta similar. I dunno what's goin on.
Part of the issue is the "hybrid" nature of the filter--it's a band-stop filter, with a cap (or RC network) in parallel to boost. It's a compromise; the notch is always present. Check out the Wiki LCR page CynicalMan posted earlier in the thread.
But with switching, you can make two separate distinct passive LCR filters with minimal components:
(http://www.instructables.com/files/deriv/FHD/ISU5/GA0O5KJQ/FHDISU5GA0O5KJQ.MEDIUM.jpg)
Here's a band-pass (boost) filter (C2 is bypassed.) Break the connections at P1 and P2, and it's a band-stop (notch) filter.
With a DPDT switch, you could eliminate C2 and route C1 in parallel or series with the inductor. Or neither, with your center-off switch.
(R2 is depth. As is, it's a placeholder. You can buy a 0 ohm resistor, but LTspice won't let you use it... :) Some resistance here will lessen the effect. R1 is for the sim, probably not needed.)
Why are the 220k and 1m resistors in the original circuit designs?
Also what would switching to the middle lead of the inductor sound like? Just half the effect?
The two resistors broaden the width (lessen the "Q factor" of the filters.) The notch, being the primary filter, is very narrow without the resistor (220K). It's one of those things you play with until it sounds right. Wah pedals usually have a resistor or two to do the same.
Changing the inductance shifts the resonance frequency. Cutting it in half would shift the frequency response higher. Changing the capacitance values would also have similar effect.
(http://i633.photobucket.com/albums/uu56/el_heisenberg/untitled.gif)
This works good. But I'm sure there are more possibilities. What about different inductors? Between my vari-tone, the mid boost/cut pot and this switch control I'm starting to really like messin with passive tone controls. They're alot nicer than the normal cap/pot ones.
Thanks, gmoon.
These sorta controls are also alot funner. I wanna keep messin with it to see how much I can get out of it, the easiest thing I can see to do right now is put a cap on one side o the switch and remove the jumper to change the caps value when its in parallel with the inductor.
But adding resistors in parallel and changing caps and inductors and inductor leads can have endless possiblities! Itd be different for every guitar. and you could tune it exactly how you like. Well I could if I could get a hande on this.]
More question: Does that 5k pot in series after the inductor in the craig anderton rotary circuit do the same thing as the resistors in parallel to the caps in the mid scoop/boost circuit?
ad i have no idea how to work this LTspice. crap
Here's another passive mid control. I won't call it a boost. This is meant as a alternative to the standard guitar tone control. This was redrawn from the Stompbox Cookbook. The pot is meant as a dual gang.
(http://www.super-freq.com/wp-content/uploads/2010/06/Picture-1.png)
Quote from: gmoon on May 26, 2010, 04:51:46 PM
Ever check out Craig Anderton's "Passive Tone Control"? It's a very similar passive LCR filter.
http://i86.photobucket.com/albums/k99/jprak1/Passivetone.jpg (http://i86.photobucket.com/albums/k99/jprak1/Passivetone.jpg)
Beats me if you can still get the RS 273-1378 inductor / transformer, but it's spec'ed at 88-100 uH.
The original schematic (from the Ele. Proj. for Musicians book) doesn't have the POT... And some of the caps are different values.
How much different is that inductor from the TL021 1.5h one I'm using. It's what I have in my rotary tone control and the mid control in the strat and the wal mart guitar.
(http://www.jpbourgeois.org/guitar/images/midboost.gif)
If the 500k resistance is too much, why does this circuit work?? When the pot is centered it's the open setting. All this time I thought it's been attenuating the signal. But I guess not. And the passive mid boost really IS a boost even tho 1 or 2 db isn't all that much volume.
(http://i633.photobucket.com/albums/uu56/el_heisenberg/untitled.gif)
^^^^^ When the switch is set so the signal goes through the cap/inductor in series it just sounds like the tone control is down a bit. I don't like this setting. The other setting, with the cap and inductor in series sounds good. Big volume drop but nice.
I've messed with the circuit a bit. (it's been in the guitar already this whole time). I only tried a few caps for the series setting, not including the .038. I tried .006, .01, and .1. I shoulda tried .047 but figured it'd sound the same. I settled on .01 cos it sounded like where I usually like my tone control, except I got a little bit a clarity it seemed. I tried putting a 180k resistor across the cap but I couln't hear a difference.
I like the parallel setting alot. like ALOT. it's real cool.
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Im guessing if I had tried the resistor across a larger series cap like the .1 uf, I might've heard the effect.
Quote from: El Heisenberg on June 05, 2010, 03:21:15 AM
^^^^^ When the switch is set so the signal goes through the cap/inductor in series it just sounds like the tone control is down a bit. I don't like this setting. The other setting, with the cap and inductor in series sounds good. Big volume drop but nice.
Quote from: El Heisenberg on June 05, 2010, 03:21:15 AM
I like the parallel setting alot. like ALOT. it's real cool.
(somewhere in there you found something you like.)
LC in parallel, you should be getting a boost of 3 or 4 dB @ ~0.7khz with the 0.038uF cap and 5 or 6 dB @ 1.5khz w/0.01uF. Plenty of attenuation above and below that; so there's a net decrease in signal overall, even with the boost. But if the boost is in the right place...it works. The series connection is a notch, but less complex than the POT filter you already installed (without the highend "pop"). A sim can show you approx what's happening, but it can't tell you if you're gonna like it... ;)
Likewise, you probably like the resonant frequencies of the POT filter. And the "pop" after the notch. I still don't think you're getting all you can with the wiring on that one...
There will certainly be a frequency shift with a 1.5H (lower) vs. a 100mH inductor.
.....
My roommate in college had an
Electra with a 5 position tone switch; certainly an inductor was involved. I used to "dis" that guitar, cause it was just an LP knockoff. That was a long time ago, wish I had access to it now... Passive LCR filters might bring something good, especially with humbuckers.
The guitar Im doing this to has the electra distortion in it that they used to put in those guitars. Maybe that's why this is working so well. With the distortion off there's alot of tone loss. But when you turn it on you can really hear what the effect is doing.
I changed my switch so that it switches between two caps in parallel with the inductor. I tried .057 and .01. I liked both, but since .057 was already in there I just left that. I think I woulda preffered .01, or maybe something like .068. With the electra distortion you can really hear the tonal change. With the .038 cap there are some point on the neck that seem to give me octaves! With the .057 the effect is lower on the neck and doesn't sound much like an octave. I wish I had more possibilities than two.