new tone pot

“The passive tone control found in most electric guitars is a simple treble-cutting series RC filter. A resistor (variable, the pot in question) is in series with a capacitor, shunted across the output of the pickup. This is a low-pass filter, the cutoff frequency of which is varied by the resistance. “

A pickup is far more complex than you consider in your statement.
The pickup's internal inductance, resistance, and capacitance form the upper portion of a voltage divider.
The ‘tone cap' and ‘tone pot' form the lower.
Also not mentioned in your assessment, was the cable capacitance and the loading caused by the amplifier.
While there will be some shift in the cutoff frequency (downward) by reducing the resistance (tone pot), this is NOT the most important function. The AMOUNT of ATTENUATION of frequencies above that point IS.

Just as we perceive volume in a logarithmic sense, so do we perceive the relative attenuation of these higher frequencies.

YOU MIGHT FIND IT INTERESTING to note.
Fender universally uses audio taper pots for both volume and tone.
Gibson on the other hand, sometimes uses linear pots for volume,
Yet ALWAYS uses audio taper pots for tone.

Having in my youth, made the mistake of replacing a noisy tone pot with a linear taper of the same value, then having the customer return the next day, I am quite aware that they result in poor usability in this application.
It was not until many years later, that I was able to understand WHY.

Oh, while I'm at it,

SoundsGood,

Take everything you read on singlecoil.com with a grain of salt.
There are a FEW decent pieces of information there..................and SOME that aren't worth the paper they're (not) printed on.

Comment by nj&ear:
This post has been altered by Admin and does not represent the entirety of the original post.
.

It is not WHAT you said, nor how you actually meant to say it, but the manner in which it is perceived by the reader. More than one reader has perceived your posts as being uncivil, so please take their views as being constructive criticism of your style, rather than the content of the post.

This Public Service Anouncement was brought to you by courtesy of the the GN Moderating Team (available for Weddings, Funerals, Bar Mitzvahs and Fancy Dress Parties) :lol:

nj&ear, I'm always happy to be educated. And I'm sure others on here are interested, too. Would you care to expound on the interactions of the pickup's internal inductance, capacitance, and resistance, the cable's corresponding qualities, and the actions of the tone control pot and capacitor? Or point us to a good link discussing all that?

For those of you with posts missing, it's just because I edited content and the quoted passages aren't available anymore.

It is not WHAT you said, nor how you actually meant to say it, but the manner in which it is perceived by the reader.
Greybeard,

I COULD be totally flippant and say, “That's the reader's problem.”……..but I WON”T.
Perhaps the more important issue is this: There are a great number of untruths on the internet. Bad advice IS bad advice. Bad advice causes people to unnecessarily waste money time, and effort. If telling someone they are wrong when they ARE, bruises their ego, so much the better. Perhaps they will re-assess what they know, and what they think they know. If a reader thinks I am uncivil and rude, well, I'll just have a good cry about it. Boohoo. Okay, I'm done now. I think you can read into that, I am much more concerned about helping people avoid making bad choices, than I am about their perception of my civility.

Case in point:
If you will Google on the terms "tone pot" and taper, you will find many recommendations on reputable sites for linear pots for tone controls.

If that is true, (I have not done such a search) then somewhere, bad information has proliferated. It likely began as an extrapolation of known good information, misapplied, similar in fashion to what we have just witnessed within this thread.

Stay tuned, as this unfolds, and you begin to see how these recommendations are wrong, and why it is important to correct them.

I edited content and the quoted passages aren't available anymore.

Nick,

You have definitely edited my content, but I find that the original passages are still there. While my citing of those passages and my specific replies to them, have been deleted. I believe you bring into question the integrity of this forum, when you alter posts without making that fact obvious, within the posts themselves. I have added comments within those posts to indicate that they have been altered. If you find my noting that my posts have been altered is unacceptable, then I believe the question is answered.

nj&ear, I'm always happy to be educated. And I'm sure others on here are interested, too. Would you care to expound on the interactions of the pickup's internal inductance, capacitance, and resistance, the cable's corresponding qualities, and the actions of the tone control pot and capacitor? Or point us to a good link discussing all that?

Ricochet,

While I do have an excellent 4th approximation of a pickup for Pspice, that took more than a year to refine, it is proprietary. There are reasonable 3rd approximation models of a pickup using singular resistive, inductive, and resistive elements. We will eventually get to that. However, since one needs to learn to walk before they can run, we will examine the 1st approximation (a simple AC voltage source) combined with the 1st order low-pass filter you described, then move forward from there.
The cutoff frequency is 1/(2piRC)

We will start by noting that the formula you provided describes the -3dB corner frequency, above that frequency, the amplitude drops a rate of 6dB per octave.

Let's take the example of a current Fender Standard Strat. I have chosen this, not only because it is very common guitar, but also because it has a peculiar idiosyncrasy of sounding ever so slightly brighter when the tone is a 1, than when the tone is at 3. The brightest sound is still at 10, which is normal. Later when we get to the 3rd approximation, this idiosyncrasy will be an interesting phenomenon to explain.

So, we will have 0.022uF of capacitance and up to 250k of resistance.

I would like you to enter the following values into your formula, and determine the frequencies:

1 : representing a value near the low end : 1% of the resistance or 2500 ohms.

2 : representing a value nearer to the middle : 10% of the resistance or 25k ohms.

3 : representing a value at maximum (10) : 100% of the resistance or 250k ohms.

Please do the math, and list the results for those 3 values.

How do these frequencies compare with the way that the tone control operates?

Does this data:

A : accurately indicate the way the tone control works.

B : follow the general direction but not necessarily the exact way that the tone control works.

C : completely contradict the way that the tone control works not only in value, but in the general direction as well. The formula obviously does not apply for some reason.

If you find the answer to be “A” we are done.

If you find the answer to be “B” we have a little more work to do, to tweak our application of the formula.

If you find the answer to be “C”, we will need to abandon the application of this formula, and be ready to move on to the 2nd approximation (AC voltage source and series resistance.) connected to the tone pot and cap, as well as the concept of a shelving equalizer.

At this point, you might also consider carefully comparing the RC network you cited, and WHERE the output is, in relation to where the output is taken in a guitar tone control.

I will be traveling again, and return next Friday, if you wish to continue.

Greybeard,

I COULD be totally flippant and say, “That's the reader's problem.”……..but I WON”T.
Taking that attitude would be totally disrespectful and ignorant.
Bad advice IS bad advice. Bad advice causes people to unnecessarily waste money time, and effort.
I agree.
If telling someone they are wrong when they ARE, bruises their ego, so much the better. Perhaps they will re-assess what they know, and what they think they know.
Utter rubbish. Bruising someone's ego is far more likely to induce intransigence and reduce their willingness to learn. The chances are that you would be regarded as condescending, disrespectful and ignorant.
If a reader thinks I am uncivil and rude, well, I'll just have a good cry about it. Boohoo. Okay, I'm done now.
This rather reinforces any impression, already gained, that you are condescending, disrespectful and ignorant.
I think you can read into that, I am much more concerned about helping people avoid making bad choices, than I am about their perception of my civility.
No, I read into it that you are condescending, disrespectful and ignorant, but, as you (don't) say, that's my problem.

If you can get rid of the condescending attitude and show some respect for the other members of GN, I, for one, will be more than happy to read what you have to say and to learn more about pickups and their workings.

Nj&ear, I can see that my original model is based on a presuption that the pickup is represented by an equivalent generator, and ignores the generator's internal impedance at various frequencies. If we take the extreme example of turning the tone control to zero, there's just a capacitance, which is in parallel with the pickup's distributed capacitance. The capacitor's impedance at various frequencies is easily calculated, but its effect on the generator's output (looking at it as a black box equivalent generator) will depend on the generator's internal impedance at those frequencies. The capacitance being in parallel with the pickup's capacitance, simply adds to it.

The pickup, rather than an idealized generator of unknown and ignored impedance, is better represented by a resistance and inductance in series, both in parallel with the distributed capacitance of the winding. And cables also have a small inductance and resistance in series, with a fairly large capacitance between the two conductors. The pickup thus (I'm going to neglect the cable for now) acts as a bandpass filter in series with a generator, the values of the capacitance and inductance determining the resonant frequency where it gives peak response and the series resistance affecting the height of the peak and the bandwidth. Nothing new here.

A problem is that we're not given the inductance and capacitance values for pickups generally, just resistance. Nothing to go on to calculate the pickup's impedance at different frequencies, without lab testing.

I don't know the proper mathematical analysis for the effect of changing a resistance in series with a capacitance that's in parallel with a parallel L-C resonant circuit containing series resistance (the pickup.) Please feel free to enlighten me and show me my error. (Where the logarithmic relation comes in.) My ego can take some bruising. :lol: (I have an intuition that it might be in working along one slope of the pickup's resonance curve.)

Like I said earlier though, I didn't make up the recommendation for a linear tone pot. There are lots of sites recommending it. If you want to correct misinformation, it would surely be more efficient to write a tutorial explaining exactly why it doesn't work that way and post it, instead of leading me through a Socratic exercise on a guitar board.

And for those who glaze over at discussions of theory and don't care, pots are cheap and easy to switch out. It's not that big a deal to try both linear and log pots and see which you like better. Post your results!
:D

If telling someone they are wrong when they ARE, bruises their ego, so much the better. Perhaps they will re-assess what they know, and what they think they know.
You don't find that people - objecting to your manner - don't care whether your information is correct or not, they'd rather get it somewhere else?