About wiring and electronics - a compilation of information?

[Christophe]

Hello to all.

I've just find this forum a few days ago, but it's so full of information that it's amazing! In fact, I absorbed so much information reading in those few days that I just need to do this thread to "compile" them!

I would like to summarize here all the information I have found about eletronics and wiring on this forum, first to be sure to find it back all in one place, but also and mainly to be sure that I have well understood everything.
I'm still having a lot of question, and I'm sure that I'm wrong on lots of things, so please, correct me when I'm wrong.

The main "threads":
- the Wiring Library
- the capacitor thread
- "Understanding Guitar Wiring" at stewmac.com

Nothing new here, again, just a "best of" of some information already present here, but maybe a bit spread between threads.

As you have already guessed, english is NOT my primary language. So I'm sorry in advance for all the errors I will do and hope for your forgiveness about that. Also, I hope this will still be enough understandable.

Here is the plan :
0 - Introduction
1 - The volume part
2 - The tone part
3 - The two main wiring : 50's and Modern
4 - Adding a twist : independance of volumes
5 - Adding a twist : NOT
6 - Changing pots effects
7 - Changing caps effects

[Christophe]

0 - Introduction
I'm concentrating on a basic les paul schema : 2 pickups, 2 volumes, 2 tones.
In fact, as both bridge and neck part are symetrical, I'm concentrating only on one part (1 pickup, 1 volume, 1 tone), as the same information applies to the other one (except for part 4).

Basic facts as I understood them:
Input = pickup. It's the sound generator. The sound is a signal made of different frequencies.
Output = switch. From the switch, the signal is send back to the jack, and to the amp.
Signal = it's the voltage between a point and the ground (always at the bottom in the schema)

Fig-0.png

[Christophe]

1 - Volume
Basic working of the volume as I understood it (it's just a basic representation, I know that not all wiring works like that):
Fig-1.png
Pot is a variable resistor, acting as a voltage divider (or here, signal reducer).
Potentiometer - Wikipedia, the free encyclopedia

The pickup signal is the voltage at the edge of the resistor.
The output signal is the voltage taken at the chosen part of the resistor (acting on the pot is like choosing where the arrow will take the signal):
- the lowest is the resistor part, the lesser is the signal.
At the limit, the resistor part is null (short-circuit), and the output signal is null.
Fig-2.png
- The highest is the resistor part, the bigger is the signal.
At the limit, the full pickup signal is took with the full resistor.
Fig-3.png
- In between, the output signal depends of the resistor, and is smaller than the full signal
Fig-4.png

Thus, acting on the volume pot is choosing the signal strength, thus the sound volume.

I will came back on pot values and type (audio versus linear) in part 6.

[Christophe]

2 - Tone
Basic working of the tone as I understood it:
Fig-5.png
Pot + cap are working like a RC circuit, that is, a low-pass filter:
RC circuit - Wikipedia, the free encyclopedia

Here is what I understood of a "ideal" low-pass filter (I know that this is not like this in reality)
- For low frequencies, the cap is like an open circuit:
Fig-6.png
The output signal is globally the same full pickup signal.
The resistor value doesn't change much to this, as even the full resistor value is small compared to the open-circuit resistor value.

- For high frequencies, the cap is like a short circuit:
Fig-7.png
the output signal depends of the resistor value.
As for the volume, the highest is the resistor, the bigger is the signal, the lowest is the resistor, the lesser is the signal.

So the low frequencies are always at full, and the volume of the high frequencies are depending of the tone pot action, from all cut:
Fig-8.png
to full:
Fig-9.png

Thus, acting on the tone pot is either cutting or letting the high frequencies.

I will came back on pot values and type (audio versus linear) in part 6, and cap values and materials in part 7.

[Christophe]

3 - Main wiring
Let say for the moment (that is, until part 5) that the position of the cap and the tone pot are interchangeable, so that the 4 following diagrams are the same:
Fig-10.png

Then, looking at all the wiring schema (for example here: Wiring Library), I think we can distinguish 2 main principal wiring:
- the "modern" (or stock) wiring:
Fig-11.png
- the "50's" (or volume pot) wiring:
Fig-12.png

The difference between the two is the place of the tone part, that is of the low-pass filter:
- in the "modern" wiring, the filter is done on the whole pickup signal, and the volume take a part of the filtered signal
- in the "50's" wiring, the volume is done first, and the filter is done on the possibly reduced signal

As ex-Les Paul Forum member 'Lewguitar' explained (as reported by "ashbass"), in the "50's" wiring, as the filtering is playing on an already reduced signal, the filtering is lesser than when applyed to the full signal.
So the 50's wiring is "preserving more treeble", as the filtering is lesser.

Another thing to note is the order of action:
- in the modern wiring, the tone control is always acting fully, whatever the volume control value is. On the opposite, the volume control is dependant of the tone control, as it is acting on the result of the filtering.
- in the 50's wiring, on the opposite, the volume control is always acting fully, whatever the tone control value is. On the opposite, the tone control is dependant of the volume control, as it is acting on the possibly reduced signal.

I can imagine for example that, for a low volume, it's easier to play on tone with the modern wiring than in the 50's wiring. In the modern wiring, even at low volume, the tone control is acting fully, whether in 50's wiring, at low volume, the tone control is playing on almost nothing, so shouldn't have much effect.
Am I right ?

To summarie, here are the differences between the two wiring :
- 50's should preserve more treeble
- modern should preserve tone action at low volume

[Christophe]

4 - Independance of volume
With both main wiring (50's and modern), here is what happens when you put the volume pot at the minimum:
Fig-13.png
the output signal is short-circuited.
And this has a consequence for the OTHER pickup (here come the second pickup) when the switch is in the middle position.
When the switch is either top or bottom position (3-position switch), there's a "direct link" between the circuit of ONE (and only one) pickup and the jack.
But when the switch is in middle position, in standard wiring, the two pickups circuits are put in parallel (the whole circuit is represented as a box):
Fig-14.png
So in fact, short-circuiting the output signal of one pickup circuit is sort-cicuiting the WHOLE output signal:
Fig-15.png

The same reasoning is good also for a chosen value of a volume pot.
I think that it's the smallest value of the two volume pot that is took. Am I right ?

This means that, in both wiring seen before, be it 50's or modern, the volume controls are NOT independants when the switch is in middle position.

So, there's the first twist to the main wiring: adding volume independance.
- modern wiring with volume independance:
Fig-16.png
- 50's wiring with volume independance:
Fig-17.png

As we see, the place of the tone part don't change for a specific wiring. It's really just a twist of the main wiring, the caracteristics of the main wiring don't change (about treeble and tone at low volume). The only thing that change is the behaviour of both volumes when the switch is in middle position.

What's really changing is what is short-circuited when the volume pot is at minimum.
In "standard" wiring, it's the output which is short-circuited. It's equivalent to short-circuiting the guitar jack, I think.
In "independent" wiring, it's the pickup which is short-circuited.
Is it good ? I don't know.
Can the pedals or the amp take a short-circuited guitar jack?
Can the pickup be short-circuited without any problem? (I remember from my basic eletronics classes that it's not goor to short-cut a generator... But here, the voltage generated is so small?)

Here, I would really like the opinion of an expert.

[Christophe]

-- Examples --
So I took all the applicable schema I could find on the "Wiring Library" with 2 pickups, 2 vol, 2 tones, and nothing else, and the game is to classify them in one of the 4 category:
- modern standard
- modern independant
- 50's standard
- 50's independant

The wiring category can completely be found just by looking at the volume pot, especially 2 points:
1 - the wiring between the tone part and either the pickup or the switch on the volume pot
=> modern or 50's
- tone linked to same lug than pickup, switch alone on the lug => modern
- tone linked to same lug than switch, pickup alone on the lug => 50's
2 - the place of the pickup and the switch on the volume pot
=> standard or independent
- pickup on the outside lug and switch on the middle lug => standard
- pickup on the middle lug and switch on the outside lug => independent

The way the tone part is linked to the volume pot (either through the cap or through plain wire) doesn't change the category.

(all schemas are property of their respective owner, I only cite them as example)

1.gif
Stock = modern standard
Volume pot = 50's standard
Tone pot = 50's standard

2.jpg
As written, modern standard

3.jpg
As written, modern independant

4.jpg
As written, 50's standard

5.jpg
As written, 50's independant

[Christophe]

-- Examples (continued) --

6.jpg
modern standard

7.jpg
As corrected (and not as written), modern standard

8.jpg
modern standard

9.jpg
NOT as written, modern standard
(there's a trap here, as there's TWO links from tone pot to vol pot. But in fact, the cap link is a false one, as the cap is in fact linked to the ground).

10.gif
(also found in Richie Fliegler Book "guitar and amp")
modern standard

[Christophe]

-- Examples (end) --

11-2.jpg
(also found here: Wiring Diagram)
modern standard

12-2.jpg
Depends on which is switch and which is pickup.
if pickup = black and switch = grey : modern independent
if pickup = grey a nd switch = black : 50's standard

13.jpg
modern standard

[Christophe]

5 - not changing mod : how to wire the tone pot
Free information, Understanding Guitar Wiring at Stewart-MacDonald
Whatever the pot (linear or audio), if you're using middle+left lugs instead of middle+right lugs, your sound won't change, but you will find that your tone control is inversed.

Swapping the two used lugs don't change anything (for example, putting ground in the middle and cap at the right, or the opposite, putting ground at the right and cap in the middle)

So, as far as I know, this doesn't change anything (AM I RIGHT?), and the 4 following schema are equivalent:
Fig-18.png

Example of real wiring for each schema:
A : I didn't find any

B :
6.jpg
9.jpg
11-2.jpg
(all are modern wiring)

[Christophe]

C:
1.gif
Only the 2 first (stock and vol pot).
Stock is modern wiring, vol pot is 50's wiring

2.jpg
3.jpg
8.jpg
10.gif
All modern wiring

[Christophe]

D:
1.gif
(Only last one, tone pot)
4.jpg
5.jpg
All 50's wiring

7.jpg
Modern wiring

[Christophe]

6 - Changing pots effects
Free information, Understanding Guitar Wiring at Stewart-MacDonald
Potentiometer - Wikipedia, the free encyclopedia

There's two things to take in account in a pot:
- the total value of the pot
- the way the resistor value change when the pot control is turned.


A - The total value is something like 250k, 300k, or 500k in general.

Concerning volume:
In theory, concerning JUST the volume, the value of the pot don't change anything, because it's the pickup that generate the signal, so the voltage. The only thing that change is the electric current generated (U = RI). The highest resistor value, the smaller electric current. But as what's matters really is the signal (the voltage), I don't think that this is really important (PLEASE CORRECT ME HERE).

(IS IT TRUE THAT A HIGHER POT WILL FILTER SOME HIGH FREQUENCY, JUST BY BEING ON THE VOLUME?)

Concerning tone:
One of the caracteristic of the low-pass filter is the cutoff frequency (fc)
RC circuit - Wikipedia, the free encyclopedia
Globally, it's the frequency that determine which frequency goes and which frequency stay.

The cap value play a role in the value of the cutoff frequency.
I also THINK that the tone pot value AND the volume pot value CAN play a role also, depending maybe on the wiring and on the position of the tone and volume pot.

But here, I haven't found any information, and my electronics knowledge is too basic for that.
So would some expert please fill in here the role of vol pot and tone pot values in the cutoff frequency value, maybe depending maybe on the wiring and on the position of the tone and volume pot? Especially, effects of high or low values pots for each wiring...
Thanks a lot.

Also, things are not perfect in reality, and the value written on a pot is a "theoric" value, but it's real value can be different, plus or minus a "tolerance" value.
Crap pot can have high tolerance values, and so you can have a real value very different from the "theoric" value.
Good quality pot either have a low tolerance value, or have been tested and selected before being sold.


B - The way the resistor change can be of two kind : linear or logarythmic
The name change between the countries :
Linear = lin = B (japan)
Logarythmic = audio = A (japan)

When linear, turning the pot control of a specific amout always correspond to the same resistor value change, wherever the pot is at the start or at the end. There's a direct mapping between the % of rotation and the % of value change.
If you turn the pot control of 10%, you will always have a 10% value change. For example, for a 500k pot:
Rolling from 1 to 2 can change resistor pot value from 50 to 100, when rolling from 8 to 9 can change resistor value from 400 to 500 (fake numbers).

When logarythmic (or audio), for the same amout of control rotation, the resistor value change depends if you are at the start or at the end of the pot. It change slowly at the beginning, and faster at the end. IS IT TRUE OR IS IT THE OPPOSITE ?
So, if you turn the pot control of 10% at the start, you may have a 1% value change (fake numbers), and if you do the same at the end, you may have a 80% value change (again, fake number). For example, for a 500k pot (again, fake numbers):
Rolling from 1 to 2 can change resistor pot value from 2 to 4, when rolling from 8 to 9 can change resistor value from 200 to 400 (fake numbers).

Another way to look at it:
- with linear, rolling one step on the control button is ADDING a specific value (always the same, for example, 50) to the resistor value.
- with audio, rolling one step on the control button is MULTIPLYING the resistor value by a specific value (always the same, for example 2).

The relationship between the control rotation and the resistor value change can be plotted as a curve. That's why we talk about the "curve" of an audio pot: it's the relationship between the rotation and the value change.
You can see an example of such a curve here :
Potentiometers (Beginners' Guide to Pots)

Why such a thing? Because that's the way our ear works. When you're cranking volume step by step, each step "similar" in volume to your ears, in fact you're DOUBLING the volume each step.
So it's natural to use log pot for volume.

Concerning tone:
Remember that the tone pot controls how much of the frequencies filtered by the low-cut filter is blended with the non-filtered one.

I don't think there's a consensus (AM I RIGHT?) for using either one or the other.

But if you find that your tone control is acting more like an on/off switch than a full-value control, it may be that you would benefit by changing the type of your tone pot: if you have a linear (B), change it for an audio (A), and if you have an audio (A), change it for a linear (B)

That's the theorie.However, things are not so perfect in nature. Especially:
- our ears are not perfectly logarithmic. Some pots are designed so that they reproduce the natural ear curve, and not the mathematical logarythmic one.
- it's hard to create "perfect" logarithmic pot. In fact, it seems that log pot are not following a "real" log curve, but are approximating it with steps. Instead of having a unique resistor component inside, the pot is composed of several different components, each with its own value.
This means that you can have very different quality audio pot, with very different curves.
Crap pot can have only three or two different material inside, thus giving you something very far from a log curve.
On the contrary, good quality pot are approching very near either log curve of specific curve, designed especially for a specific use (be it volume or tone)


So, to summarize:
There's two things to take in account in a pot:
- the total value of the pot
- the way the resistor value change when the pot control is turned.

Concerning volume, the value of the pot doesn't change anything, and you will use audio pot for natural reasons

Concerning tone, you can MAYBE change the way the frequency are filtered by changing the value of either or both volume and tone pot, maybe depending on the wiring and the tone and volume pot position.

Concerning tone again, I don't think there's a consensus (AM I RIGHT?) for using either one or the other, but if you find that your tone control is acting more like an on/off switch than a full-value control, it may be that you would benefit by changing the type of your tone pot.

Finally, concerning volume and tone, you can have better control on volume and tone by buying good quality pots with good curve, or even adapted curve for specific usage.


Then, there's all the "defective" behavior that some components may have, and that would induce "specific" effects.
If any experts have opinion about those?

[Christophe]

7 - Changing caps effects
Or why changing cap can really have an effect on my sound, scientifically.
The "Sound" of Capacitors
The capacitor thread.

There's two things to take in account in a cap:
- the total value of the cap
- the dielectric constant of the cap, which (IF I UNDERSTOOD WELL) could be compared to some linearity of the capacity depending on the signal sent (AM I RIGHT?)


A - The value of the cap is directly used to compute the cutoff frequency.
The higher the value, the lower the cutoff frequency
The lower the value, the higher the cutoff frequency

As Paul explained in "The capacitor thread.", the lower the cutoff frequency is, the more frequency are filtered, starting with very high, then high, then high medium, then medium, etc. So a low cutoff mean that your filtering a lot of frequency, maybe all treeble and a bit of medium (fake values).
On the opposite, a high cutoff frequency only filters very high frequency, thus maybe leaving intact medium and part of treeble.
So if you want to keep treeble, use a high cutoff, thus a lower cap value.
If you want to filter every treeble, use a low cutoff, and thus a high cap value.

Don't forget that the tone pot control how much those "filtered" frequencies are blended with non-filtered ones:
- Tone pot at the max : blend all "filtered" frequencies (no filtering)
- Tone pot at the min : blend none of the "filtered" frequencies (full filtering)
Thus Paul remark: the cap is having almost none effect when the tone pot is at the max

Here again, things are not perfect in reality, and the value written on a cap is a "theoric" value, but it's real value can be different, plus or minus a "tolerance" value.
Crap cap can have high tolerance values, and so you can have a real value very different from the "theoric" value.
Good quality cap either have a low tolerance value, or have been tested and selected before being sold.


B - The dielectric constant
The lowest the dielectric constant, the more linear the cap is, the better it is for audio. Best is near 2.
The dielectric constant is function of the material in which the cap is build.
Guitar Caps (sorry, it's in french - you will find the value on the right)
- Polycarbonat K=3
- Polypropylen K=2.5
- Polystyren K=2.2
- Paper on Oil K=2.2
- Ceramic K=5 to 100

So, to summarize:
There's two things to take in account in a cap:
- the total value of the cap
- the dielectric constant of the cap, fixed by its material

You can change the domain of frequency that your tone control act by changing the value of the cap
higher value -> less treebles
lower value -> more treebles

You can change the way the frequency are controled by your tone control by changing the material of your cap. AM I RIGHT?

Then, there's all the "defective" behavior that some components may have, and that would induce "specific" effects.
If any experts have opinion about those?

[Christophe]

=== FINAL ===

So here is my compilation of all information. Again, PLEASE correct me if I'm wrong or even just incomplete or fuzzy.
Thanks a lot for your help.