Tone Knob

[eidlyn]

So I'm thinking about building a Jaguar from Warmoth parts, or just get a Japanese HH Jaguar Special, the black one, which I absolutely adore, and once again met with a series of questions that I don't have answers to.

The first one is that no matter which one I get, I want to change the tone knob because (i'm sorry guys) i cant stand the muffled tone i get when i roll it down, so i was thinking put in a cap or resistor that doesn't simply clip all the high frequencies if one exists, but just gives it a bassier sound or at least some contour. Also, I had heard that Fulltone pedal makers had the same complaint, and put in a wah-inductor as a mid-control on one of their pedals- would that work for a passive guitar?

The second question is that if i do build my own, would it sound at all like a jaguar if i threw in lily frailin strat-single coils, or even paf pickups, or should i just go with duncans?

[52 Bill]

...put in a wah-inductor as a mid-control on one of their pedals- would that work for a passive guitar?

Yes, using a coil (L) with the cap (C) and tone pot (R) will work. The two things to read up on are Craig Anderton's passive tone control from his project book and LCR tone networks in general.

...would it sound at all like a jaguar if i threw in lily frailin strat-single coils, or even paf pickups, or should i just go with duncans?

There are IMO two parts to what makes a Jaguar sound like a jaguar; one the mechanics of the guitar (scale length, bridge/tremolo set-up, etc.) and two the pickups and wiring. I think that there really is no other pick-up that sounds like the Jaguar pick-up. If you change them for strats or for HBs, you will change the sound of the guitar.

Just my 2 cents.

[eidlyn]

Yes, using a coil (L) with the cap (C) and tone pot (R) will work.

Is an inductor a coil or are you referring to the pickup? I can't seem to find any sites on LCR guitar wiring, and i don't understand why you would need the cap if you have an inductor. I appreciate you guys' patience, while i aced resistors and capacitors in physics we never quite got to this level.

I think that there really is no other pick-up that sounds like the Jaguar pick-up.

I read somewhere that Jaguar pickups were in fact the same as strat pickups only with a little bar on each one for adjusting something or other subtle. Btw i tried the japanese hh jaguar special, do those pickups sound at all like the original jaguars?

[eidlyn]

k so i found craig's book, and read the passive tone control, but i really don't understand what it would do, except maybe remove a few frequencies.

would i need to put that whole circuit into my guitar, and for anyone who's built it, what does the depth do? he said it can be grounded out, so i could actually just use the tone knob for the other switch.

can i just wire the inductor in the cap circuit, and wire it in series with the cap?

Also, i saw something called the q filter which seems to be the same thing that i'm trying to build, except that it just makes it sound like an acoustic steel string. if i put a higher value cap in would it give it that darker tone?

just to recap, the point of putting in the inductor is even out the frequencies so that when i turn the tone knob, it does same thing as most other stock tone knobs, only make it sound less muffled as is my complaint with stock tone knobs

[Mark Hammer]

I have made a couple of the EPFM passive tone controls, and they do some interesting things, but you don't want them on your guitar. Why? because they eat up a lot of signal, that will make it difficult to drive a compressor, or distortion, and also degrade the signal-to-noise performance of things like chorus, flanger, or phase pedals if you go straight into them. Ideally, you want something that maintains as hot an output signal from the guitar as possible.

The Jaguar has a couple of things that make it sound a little different. One is a switchable cap between the pickups and volume pot that takes the lows right out. The other is the extra little bracket that fit under and around the pickup to introduce some qualities found in the P-90 and Lace pickups where the sensing field is brought around to the sides.

If you wanted an easy way to achieve more tonal flexibility with minimum cost, I would suggest implementing something like the single Tone control found on many early Fender amps.

Normally, a Tone control uses two of its solder lugs and provides a variable resistance between the input of the volume pot and a cap to ground. This bleeds off treble to the degree set by the control position and pot resistance. (If you simply want to shave off a bit of treble and not aim for full mute, then reduce the value of the cap. If it is .047uf, switch to .022 or even .01.).

What you will often find on Fender guitars is a "compensation cap" straddling the input and wiper lugs of the Volume pot. This retains more of the highs as you start to turn the volume down and "load" the next device in line, by providing an express lane for upper treble that sidesteps the volume pot. The "bright" switch found on many Fender amps or on the bright channel of Marshalls, switches such a cap in and out on the amp's volume control for the same effect. These caps are usually small value to restrict their effect to just the upper treble.

On old tweed amps, the Tone control would be a mixture of both treble cut and treble bypass, as seen in this tweed Princeton schematic: http://www.ampwares.com/ffg/schem/pr...f2-a_schem.gif Here, the volume pot is the one with the wiper arrow pointing to the left and the tone control is the one above it.

The tone control has its wiper tied to the input of the volume pot. One of its outside lugs is tied to ground through a .005uf cap and the other end is tied to the Volume-pot wiper through a .0005uf (500pf) cap. Set to its midpoint, the Tone pot places 500k of resistance between the volume pot and the cap to ground, and 500k of resistance between the input of the Volume pot and the bypass cap going to the wiper. So, a tiny bit of treble cut, but a tiny but of treble bypass to counterbalance. As the tone pot gets rotated in one direction, the amount of treble bypass is reduced while the resistance to ground is reduced permitting treble to bleed off. Rotating in the other direction, treble cut is reduced, while the amount of treble bypass is maxed.

If you used a 1M pot wired up to your guitar volume pot, with a .015uf cap on the bass side, and a .001 to .0015uf cap on the treble-bypass side, you would be able to achieve a similar effect, ranging from a rounder bassier tone (but not full mute) to a tone with plenty of midrange twang as you turn the volume down a tad to let through the mids and highs preferentially.

[David Schwab]

k so i found craig's book, and read the passive tone control, but i really don't understand what it would do, except maybe remove a few frequencies.

It notches out midrange. If you use a single cap with a coil and a pot, you have a passive midrange control like on the Gibson L6-S.

I replaced one of the tone controls on my '81 Les Paul Standard with a 6 position Varitone, which is pretty much what the Anderton circuit is. It's a very useful tone control. I was able to go from regular LP tone, to clean bright jangle with a few clicks.

Another thing for people who don't like tone controls is to chgange the cap to a much smaller value. Something like .002 or .005 MF. it just takes the top end off, and leaves all the midrange. And gives a nice resonant peak.

[Mark Hammer]

One of the down sides of the stock EPFM/Varitone circuit is the need to put up with the audible click when switching between settings. One can get past this problem by selecting between different series combinations of caps rather than selecting between different alternate caps. Caps in series have an effective capacitance value calculated similar to parallel resistances. So: 1/C = 1/ca + 1/cb + .....1/cx A .022 and .047uf cap in series yield an effective capacitance of .015uf. A person can pick values to achiev some desired outcome and selectively shunt combinations by "tapping" the series at different points.

I've boxed up a couple of these things, two of them with an Alembic Stratoblaster JFET preamp that adds some signal boost to compensate for the passive loss when the notch becomes too wide and deep. A third one was boxed up with a switch to select bypassing of the caps, inductor or both, providing a variable highpass, lowpass, and attenuator in addition to the variable notch. very useful.

[eidlyn]

I really appreciate the help. I also just figured out how to put my issue into words. On a Jaguar, there's the the Rhythm circuit, which has 1 meg pots, and there's the lead circuit, which has 50k pots. When either the lead and rhythm circuits are on, with the tone control wide open, they sound fantastic, but the problem comes in when i try to turn down the tone on either circuit, it becomes all muffled.

Since when more impedence is put on, the tone gets darker without becoming muffled, would it be possible to simply put on more impedence as you turn the tone knob, and thus achieve various tones that sound similar to tones in between 50k pots and 1k pots.

PS. I'm looking at my cousin's $150 epiphone sg, and on the tone knob (it only has one) i see one lug that is attached to the volume pot, the middle one has a cap on it, and the left one has nothing on it. Does the cap on the middle lug cut or preserve the high frequencies?

[Mark Hammer]

Some basics: The pot divides up the total resistance it provides via the wiper - the middle moveable contact (you can easily pry the tabs and take a pot apart to understand a bit more about it or read "The Secret Life of Pots" at www.geofex.com). If you tie one outside lug to the volume, and connect the wiper to ground through a cap, you are varying the resistance between that connection to the volume pot, and the cap, as the tone knob is moved. Depending on the way it is wired, that will either be clockwise or counterclockwise. In the case of tone pots, adding more resistance reduces the treble-cutting/bleed effect of the cap, so the pot is wired up to add resistance in series with the tone cap as you rotate clockwise.

That cap will ALWAYS bleed some treble to ground. If the cap value is small enough, the bleed will affect only those highs well outside the range of the pickups. Alternatively, if the cap has a reasonably large value, and the resistance is made high enough via the pot, then negligible bleed will occur. In a great many instances, one can generally hear the difference between having the tone pot turned up full and completely disengaging the tone control/pot, underscoring the principle that the tone pot always bl;eeds a little bit.

What some folks do to eliminate the constant bleed is use a "no load pot". With such a pot as you rotate the wiper past a certain point (near the end of rotation), the resistance suddenly goes from whatever the value of the pot is (250k, 500k, etc) to infinite. This can either be through coating the little resistive strip inside so that the wiper doesn't contact it, or by cutting the resistive strip. Anything that makes the resistance in series with the tone cap high enough effectively eliminates the bleed. On one of my guitars, I simple have a 3-position toggle switch that gives me a nice "rounding" of the tone, a muter sound, or completely disconnects any tone cap for the brightest sound. Easy to do and nice and predictable.

Looking at the Jaguar wiring ( http://www.blueguitar.org/new/schem/_gtr/jag_jazz.gif ) I see that the two alternate sets of controls consist of one where the the tone pot is 50k in series with a .01uf cap, and another where the tone pot is 1M in conjunction with a .01uf cap. That second one, however, uses all 3 lugs and a 56k fixed resistor straddling two of them. This 56k resistor is not shown in the diagram found at the Seymour Duncan site ( http://www.seymourduncan.com/support...hematic=jaguar ).

I thought I'd try to "explain" how the various Jaguar controls work, but quite frankly, the wiring diagram on this beast is no substitute for a proper schematic, and since I'm writing from work (where there ARE things I'm supposed to do to earn my salary), I'm going to set that task aside for the moment. Suffice it to say that the thumbwheel tone pot is pretty dang small for a tone pot. If it were possible to easily replace it with a larger value that'd be one thing, but these are rare birds. So' i will suggest two strategies to experiment with. One is to replace the .01uf cap with a smaller value, like .0047uf or maybe even .0039uf. The other is to simply unsolder the end of the tone cap on the thumbwheel control and solder a small-value fixed resistor in series with it so that the pot is now connected to a resistor/cap network to ground. If that resistor were, say, 47k then the total resistance in series with the cap would be 97k when the thumbwheel pot is turned up full, and 47k when it is turned down all the way. A teeny bit brighter when up full, and not quite so dark when turned down.

[eidlyn]

Ok that was huge, mate. I thought the pots provided impedence. i could just put on resistors instead of caps, or a combination of the two, to get the sound i want, right? If theres more resistance, then does the sound get brighter or darker?

also i looked up the jaguar on youtube and they showed what all the switches did, with the low pass filter and the on-off switches for the pickups, and the switch for the rhythm circuit. its not that i don't understand what they do, there just isn't a "crack open your guitar and heres what everything does" guide.

[eidlyn]

also, what's with the wattage on the resistors?

[David Schwab]

One of the down sides of the stock EPFM/Varitone circuit is the need to put up with the audible click when switching between settings.

Right. The real Gibson circuit uses 10M pull-down resistors to drain the charge from the caps.

[Mark Hammer]

Think of your signal as a bucket full of earth. In that bucket are fine grains of sand, small "pebble-ettes", pebbles, and rocks. If the bucket has some tiny holes, you'll possibly lose the fine-grained sand out the bottom, but not the pebbles or rocks. Make the holes bigger, and you'll (possibly) lose the pebbles. Close any of those holes, and you lose less of whatever can fit through them.

The cap value essentially determines the "size" of the hole (what you can lose), and the resistance determines how well that hole is patched up (how much of it you can lose). Higher resistance - whether provided only by the tone pot, by a fixed resistor or by a combination of the two - is a bit like patching up the hole provided by the cap so that less leakage occurs.

As for wattage, a normal 1/4 watt resistor will do just fine.

[eidlyn]

So if i had a resistor and no cap, would the resistor anything? I was thinking of replacing the 1M tone cap with a 50k, putting the hot wire on the left most lug where the cap is now, taking off the cap, and putting a 1M resistor on the left where the hot wire is and connecting it to the back. In this fashion, when the tone knob is full on, i would have 1M05 resistance and it would have about the tone it does now, and when you rolled back the tone, it would have 50k resistance, and would have a much darker tone; is my reasoning correct on this?

[Mark Hammer]

Here you are getting into the area of "loading".

Normally, if you have nothing between the guitar and amp save for a cable, the amplifier "sees" two things at the guitar jack: the resistance from the volume-pot wiper to ground, and the resistance from the volume-pot wiper through the pickup to ground. The amp will essentially "prefer" to amplify the lower of those two resistance/impedances, and the bigger the contrast between them the greater than preference. Moreover, there will be less treble loss over the cable if that difference is very large. This is why HB users/guitars have 500k volume pots (so as to preserve treble) and SC guitars/players have 250k volume pots (so as to deliberately lose a bit of "harsh-sounding" treble).

Okay, imagine you have the volume pot turned all the way up (pot wiper at one end). What the amp sees is the full resistance of the pot, whether 250k, 500k etc, and the resistance of the pickup (probably somewhere in the vicinity of 6-8k). Big contrast. Turn the pot down a bit and some of that pot resistance now shifts to being in series with the pickup. Let's say we shift 100k of a 500k pot over to the pickup side of the wiper. Now we have the amp seeing 106k on one side and 400k on the other. Not so much of a difference anymore. (That lack of difference is why Fender guitars stick a bypass cap on the volume pot to hang onto treble.).

Okay, imagine that you have a resistor going from the point where the pickup connects to the volume, to ground. Let's say we have a 500k pot and a 220k fixed resistor. When the volume is turned up full, the amp will see a pickup (6-8k) and the parallel resistance of 220k and 500k, or 152k. 6-8k vs 152k is not as big a contrast.

Turn that volume down even a smidgen, and things change. Now what the amp sees at the volume-pot wiper is 6-8k in parallel with 220k PLUS whatever portion of the pot's resistance sits on that side of the wiper. Let's say its 50k. So we have 450k on one side and 50k plus 6-8k in parallel with 220k, which is just under 57k. Again not much of contrast to start with and not much of a contrast after a wee bit of adjustment.

Craig Anderton had a little DIY project in Guitar Player a couple years ago that he called a loading simulator or something like that. Essentially what he proposed was to use a 1M volume pot (minimum pickup loading and maximum treble preservation) and have a rotary switch to add progressively smaller fixed resistances to ground in the manner you described. This would effectively shave off the treble available at max volume, and also alter the progressive loss of treble at less-than max volume settings in the manner the musician desired. Given that some folks like the "brittle" sound of SC pickups for some music but desire a "rounder" tone for other music, used with 1M volume pots instead of the 250k pots often recommended, this would let you have your cake and eat it too.