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Tone Capacitors, values vs sound


rhoads56
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I actually know something about this... Coool.. That's a first.. :D

Capacitors have an impedence that's indirectly proportional to the frequency of the signal passing through it.. The higher the impedence, the In English, that means a capacitor actually blocks off lower range sounds.. The higher the value of the capacitor, the lower the impedence at a specific frequency... What this means is if you put a capacitor with a big @ss value in series with a pickup, nothing much would happen 'cause the low impedence would let everything through.. Put a small value capacitor in series, though, and you've got a high pass filter (ie knocks off the lower range)..

When you put the capacitor in parallel, it does kinda the opposite.. A large value capacitor in parallel would block off almost everything while a small value one would act as a low pass filter (ie knocks off the treble).. A tone control works like that.. You've got a capacitor in series with a pot which are then both in parallel with the pickup..

Practically, having a higher value capacitor in your tone control would bleed off more treble when you crank the tone all the way down.. The down side is that your overall tone would be muddier due to the fact that some signal will still pass through the capacitor even when the tone is maxed out..

Usually, when your tone pot value is high (500k), you'd use a higher value capacitor such as a 0.047uF or a 0.033uF one.. With a smaller pot value (250k), 0.022uF or 0.01uF capacitors are usually used.. No hard and fast rules here, though..

Sorry for the long, long post.. B) Hope it was worth the read!!

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Ok, im an absolute electronics dumbo. Please bear with me while i get my head around this...

From what your saying, a 250k pot, with a .047uF cap, would allow more treble to be bled off, when the tone is fully down. ?????

What effect does the cap have on a tone control that is fully up, eg: on to the maximum setting?? Or does it have zero effect??

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The formulae for calculating the impedance wrt Frequency are as follows:

Capacitor Xc = 1/(2*pi*F*C)

inductor is Xl= 2*pi*F*L

2*pi*f is so common it is sometimes abreviated with a lower case Omega (like a rounded w) so you might see Xl= wL or 1/wC.

The pot is put in series with the capacitor and is a resistive load ie (does not depend on frequency so the total impedance to any given frequency is the Capacitive Impedance Xc as above plus the pots resistive impedance for whatever setting its at (eg a 250k would have a value of 125k at ita half way point,tone pots being linear taper). Do a few calcs for different (guitar) frequencies and you'll soon see how things work.

Also have a look here: Impedance R.G explains things in quite a bit of detail.

Keith

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The formulae for calculating the impedance wrt Frequency are as follows:

Capacitor Xc = 1/(2*pi*F*C)

inductor is Xl= 2*pi*F*L

2*pi*f is so common it is sometimes abreviated with a lower case Omega (like a rounded w) so you might see Xl= wL or 1/wC.

The pot is put in series with the capacitor and is a resistive load ie (does not depend on frequency so the total impedance to any given frequency is the Capacitive Impedance Xc as above plus the pots resistive impedance for whatever setting its at (eg a 250k would have a value of 125k at ita half way point,tone pots being linear taper). Do a few calcs for different (guitar) frequencies and you'll soon see how things work.

Also have a look here: Impedance R.G explains things in quite a bit of detail.

Keith

Where are those spanish translators when we need them???

Keith, any chance of simplifying what you said, for the electronicly clueless??

Please, break it down as simple as you can.

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Hell I thought that was simple. Sorry when one lives with this stuff most of your life you tend to forget others are not as mathematically trained.

Essentially if you look at the Xc formula and stick in some values Xc = 1/ 2*pi*F *C you will see that the higher the C value the lower the impedance (or resistance to a given frequency) and vice versa of course so if you stick a capacitor across a pickup ie in parallel with a frequency of Zero you have an infinite impedance e nothing gets shunted (you can't divide by zero but mathematically: the limit of Xc tends to infinite as F tends to 0) As the value of F increases the impedance to it will drop so your highs will be cut more than your lows. Sticking a variable resistor in series with it allows you to adjust the total impedance ie Xc + R giving a variable tone control.

You could use a variable Inductor as well to give you a similar effect but inductors are expensive and prone to noise pickup (after all they are coils just like your pickups) Combinations of inductors and capacitors can be made up into filters which will block or allow any frequency band through that you care to stipulate as in cross over networks on hi-fi speakers and in fact the older analogue telcom systems relied on this to mutiplex and split speech channels.

Hope that explains things a bit simpler.

Keith

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Ok, let's see if I can remember what was taught in all those electronics lectures I slept through... Basically, impedance can be thought of as resistance of sorts.. A kind of obstruction to the flow of electricity through the circuit... Another thing to keep in mind is that each note has its own frequency.. For example, an A4 has a frequency of 440Hz.. The formulas that Keith posted will give you the impedance for a certain frequency... The first formula, in particular, shows that as the frequency of the note gets higher (higher in pitch), the more resistance the capacitor is going to put up when faced with a flow of electricity..

In English, it blocks the lower pitched sounds more than the high pitched ones... (Isn't school just so full of crap??) :D

A tone circuit looks something like the one below.. The zig-zagged lines represent the tone and volume pots, which are actually variable resistors...

Let's say the pot is 250k.. This is actually the max resistance the pot can show.. Let's say as well that the capacitor is a 0.022 uF one... Let's also take 2 notes, an A6 (1760Hz) and an A1 (55.0Hz)... Using Keith's formulas, you'll get an impedance of 4.110k for the A6 and 131.53k for the lower A1... As you can see, the A6 is gonna get a lot less resistance to it's flow...

Bearing this in mind, let's look at the circuit.. At position 1 (solid arrow), the tone is cranked to the MAX... What happens is that the impedance from the capacitor is added to the 250k resistance which the pot is now showing.. When this happens, both the A6 and the A1 now have a RELATIVELY similar amount of resistance to their flows.. What this means is that much of the signal for both notes will go into the volume pot and out to your amp...

When the tone is all the way MIN at 2 (dashed arrow), the tone pot is actually taken out of the circuit (so to speak).. This means that the difference in resistance seen by the A6 and the A1 are now RELATIVELY different, with the A1 seeing much more resistance.. What then happens is that the A6 would go into ground (and into oblivion) while the A1 would go to the volume pot and out to your amp, resulting in a muddier, bassier sound...

One last thing to note (in relation to your question, Rhoads) is that with any tone circuit, there is always going to be a little bit of signal running off into the ground, even if your tone pot is maxed out.. What this means is that if you use a 0.047uF capacitor with a 250k pot, you will get less treble even when your tone is up all the way.. You can get a clearer sound by using either a smaller cap (0.022uF) or a bigger pot (500k).. This is again that relative difference thing..

I hope this is clear.. Quite frankly, it's not the easiest thing in the world to understand.. I think I'll go play my guitar for a while.. With the tone up, of course.. B)

ToneCircuit.jpg

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Keith, any chance of simplifying what you said, for the electronicly clueless??

Please, break it down as simple as you can.

For the electronically clueless, many manufacturers are using .022uF capacitor. That's what a lot of people consider a "normal sounding" tone control. If you go up to a .047 or higher, it will remove more treble and be more muffled sounding. If you use a lower value it will remove less treble. You could go higher if you're trying to get a smoother, jazzier sound, or lower if you want to just "take the edge off" of a bright bridge single coil without losing as much definition. Using a value that's too high will really reduce your output along with the treble, since guitar is heavy in upper mids. The higher values will also "bleed off" more treble when at "10" because of the resistance inherent in the potentiometer. Very loosely put, a 250K pot turned all the way up is kind of the same as a 500K pot turned down slightly.

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Great explanation Stalefish.

One last thing to note (in relation to your question, Rhoads) is that with any tone circuit, there is always going to be a little bit of signal running off into the ground, even if your tone pot is maxed out

There is a mod you can do on your tone pot, if it can be opened without breaking it.

Open it up and cut the carbon track away from the external lug that is at it's max position. Now when you turn the pot to max it will disconnect the pot (and the capacitor in series of course). Turning the pot slightly "on" will connect it and the tone circuit.

There is a tutorial on site about it: Tone pot mod

Keith

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  • 4 months later...
  • 4 weeks later...
  • 1 month later...

heres an easy way to calculate the aproximate filter freq for a rc network. ie which is what a guitar tone control is.

http://www.muzique.com/schem/filter.htm

enter your capacitor in mF and your resistor ie pot in ohms

cheers

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  • 5 months later...
Ok, im an absolute electronics dumbo. Please bear with me while i get my head around this...

From what your saying, a 250k pot, with a .047uF cap, would allow more treble to be bled off, when the tone is fully down. ?????

What effect does the cap have on a tone control that is fully up, eg: on to the maximum setting?? Or does it have zero effect??

The lower the value of the pot, and/or the higher the value of the capacitor, the more treble that will be rolled of, or the "darker" the sound.

And yes, the tone control still has an effect even when it is turned to "10". The higher the pot value, and/or the lower the cap value, the less of this effect there will be.

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Thanks, i think we answered this a year ago :D

How did this thread get dragged up from the dead???

Sorry, I didn't look at the date. I just noticed that a lot had been written, but that your question had not really been answered.

It does seem that this board can be a slow mover. It is easy to post on a thread that is a yr or more old.

Again, my apologies

Edited by noplugsjustinfo
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  • 2 months later...

Hey I thought that this question would be a good one to ask in this thread so...

I'm making a guitar with only 1 pickup, a bridge positioned Humbucker, and it'll have a volume and tone. I have to use 500k pots. So should I use a .2 or .5 capacitor? I like the sound of putting the tone to zero on my strat on the bridge pickup, but this will be with a Seymour JB, so I don't know what I would like for that certain muffled sound when turned down.

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