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Can someone please explain to me what tone pots are, and how they affect the sound of a guitar? Thanks very much :)

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2 Answers 2

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A potentiometer is basically a variable resistor. When it's turned all the way one way, it has no resistance, and when it's turned all the way in the other direction, it has its maximum resistance.

A pot has three soldering points: its input, its output, and ground. So when the output of your pickups is wired to the input of the pot, the pot splits the signal in two directions, one of which leads to the output jack of your guitar and the other of which leads to ground. The signal from the pickups wants to go to ground, but if the pot is turned to its maximum resistance, it acts as a block to the signal, which then has to go to the output of the guitar instead. As you turn the pot, its resistance weakens, so more and more of the signal escapes to ground instead of going out the guitar's output, and so you perceive this as lower volume. So the pot acts as the volume knob.

Same thing with the tone knob. If you combine a pot and a capacitor with the capacitor going to ground, you get a low-pass filter, meaning a circuit that allows low frequencies to pass through but blocks high frequencies. The combination of the values of the capacitor and the resistor determines the frequencies which the filter sees as "high" and those it sees as "low". As you turn the pot, the filter sees more and more frequencies as high, and so it allows fewer of them to pass through. Hence, the guitar's output signal contains fewer and fewer high frequencies, and boom: tone knob. Here's a simple circuit diagram, and it's exactly what's in my guitar---except for not showing the volume and pickup switch, it's not oversimplified at all:

Tone Control Circuit Diagram

The (very) basic jist of a capacitor is that it can "store" current, but it takes some time to charge up and down. When it's charged down, a capacitor acts more-or-less like a wire, and current passes through it with no problem. Once it's charged up, though, it won't let any current through (it's at "capacity", if you will); in that state, it's like a broken wire. High frequencies alternate so rapidly that they don't give the capacitor a chance to charge up, so they pass right through it; low frequencies, however, charge up the capacitor before they get through it, and so they're blocked.

So as you can see from the diagram, if the pot's resistance is low enough to allow the signal to head towards ground, the high frequencies will pass through the capacitor and escape, while the low frequencies still can't get by the cap and have to go to the guitar's output. And so you hear the low frequencies but don't hear the high ones. Of course, if the pot's resistance is all the way up, then none of the signal goes towards ground and all of it goes to the output.

You can easily tweak your tone controls by replacing the capacitors with different ones with different values. It's a simple soldering job, capacitors are dirt cheap (like $0.10 cheap) and it's much easier than replacing the pots.

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Great answer Alex! It would be more illustrative with a picture though. Another good article on this subject is located here: stewmac.com/freeinfo/Electronics/Pots/w101-tonecontrol.html –  Jduv Jan 20 '11 at 0:38
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Similar to the tone control, a capacitor can be put across the volume pot so it acts like a high pass filter, allowing more highs to pass through as the volume is rolled down. This mod. on a Les Paul can clean it up when you roll the volume down, making chords, especially complex ones, really sparkle when you drop back for rhythm work. I used to do it to all my Gibsons. The linked article specifically says single-coils will gain more, and, yes they would. I always used little pre-amps in my strats which took care of the problem entirely. –  Anonymous Jan 20 '11 at 1:09
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+1 to tin man. This is a good mod often referred to as the "50's wiring mod". I.e. that is how Gibson guitars were wired back then. I really recommend wiring a Les Paul like this if you get a chance, particularly if you're into blues or classic rock. For extra tone, buy some "vintage" pots and caps from a place like RS Guitarworks (store.rsguitarworks.net) –  Anonymous Jan 20 '11 at 2:39
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That actually is NOT vintage wiring. PLacing a capacitor across the volume pot is called a treble bleed capacitor, and it's usually paired with a specific resistor depending on the type of potentiometer you are installing them on along with the output of the pickups. The so-called "vintage" wiring on Les Pauls is very hard to nail down because each guitar could have been wired completely different. A diagram of true '57 wiring (the only consistent one to my knowledge) is located here: lollarguitars.com/pickup-wiring-diagrams/… –  Jduv Jan 20 '11 at 3:00
    
If you'll notice on that diagram, the older way of wiring a tone pot included placing one post at the sweeper lug on the pot and the other post on the input to the tone control. This compensates for a volume drop that occurs as the logarithmic taper of a potentiometer kicks in. When you roll the volume back some of the frequencies that were bled off are allowed back into the output signal, keeping it consistant. The drawback to this schema is that the tone value changes as you move the volume--so every time you change the volume you have to tweak the tone pot to keep the tone uniform. –  Jduv Jan 20 '11 at 3:06

The tone pots are literally the knobs on the front of your guitar that you adjust the tone and volume of your pick ups with.

Edit: Cant explain in any great technical detail; aside from to say that they allow you to control the low power analogue signal of your pickups.

In the case of the Tone pots these allow you to control output from specific pick-ups with the volume pot controlling overall volume.

The toggle switch allows you to choose individual/combinations of pickups; with the tone pots acting upon those selected.

Depending on the type/configuration of the guitar you have, you may have a tone pot for each pickup (this gives you most tone control); or you may have one tone pot which controls the overall tone of whatever configuration is selected via he toggle switch.

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Could you elaborate? :) –  Ali Maxwell Jan 19 '11 at 22:11
    
Not brilliantly see above –  DRL Jan 19 '11 at 22:43
    
I don't believe toggle switches are, in fact, pots. When a pot is described as "linear", that refers to the rate at which the resistance changes as the pot is turned. –  Alex Basson Jan 19 '11 at 23:13
    
Your probably right; i don't know a great deal about electronics. regardless i have removed that from my answer. –  DRL Jan 19 '11 at 23:21

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