#1
Okay so I was having a conversation with a friend about guitars.
His el-cheapo refused to make noise. I just told him to open it up and look
to see if any wires had shaken loose. This lead to a very global question
about wiring. How do tone pots work?

Well the last time I wired a guitar it was a jazz bass (and why it was fresh in my mind I don't know since the last wiring I had studied was for a Tele) So I said something along the lines of:

Well the signal from the pickups go into the volume pot. When you have the knob to zero it bleeds off all the signal into the ground. When it is at ten it only bleeds off a little. From there the signal goes into the tone pot, where the knob decide how much signal goes through the capacitor and how much high frequency is bled off. From there it goes to the jack.

He pulled out a wiring diagram! (I don't remember where we were, but this seemed a little odd) He pulled out a Seymour Duncan 2 Hum, 1 vol, 1 tone, 3-way, push/pull . Oh he picked a doozey since I have not given a whole bunch of thought to how these things work. It's not a straight line where the signal is progressively filtered off until it leaves the guitar. And what follows is what I could use a little help with making sure the explanation is correct.

First is the push/pull. When soldered together the series link wires do nothing. When you pull up the knob you connect the series link to the ground and that coil's output disappears through the ground. Then the hot lead leads to the the switch. Depending on what you tell the switch, that is what is sent to the volume pot. (oh by the way, the push/pull is just a little unit that is strapped to the bottom of the volume pot)

Depending on where you adjusted the volume knob, this is how much signal is sent to the ground instead of the jack. Okay, I think I'm good up to this point. But how does the tone circuit work? It is not like the Jazz Bass where the pots act like a series of consecutive filters. The output come from the center lug of the volume, it never goes into the tone pot. Instead, in this configuration, does the tone pot act like a vacuum? The closer you turn the tone pot to 10, the more signal it pulls out of the volume pot.

Oh wait, I think I've answered my own question. Electricity, given the chance, will always flow to the ground. All the electronics of a guitar influence how much (and in the case of tone) what type of signal is give a chance to go to ground instead of being coerced toward the jack.
Last edited by gs_790 at Oct 29, 2008,
#2
You've rambled a bit, so hopefully I'm answering the right question - a tone control is a low pass filter - This text explains it better than I could.

# Tone Control(s)

A Guitar's tone control is actually a very simple low pass filter comprising a capacitor, and a potentiometer wired as a variable resistance in series. This type of circuit is called a "first order" filter, and has the effect of gently rolling off frequencies above a certain point determined by the combined AC reactance of the capacitor and the DC resistance of the potentiometer. Typical capacitor values range from 10nF (0.01µF) to 100nF (0.1µF), usually the resistance of the pot is the same as that of the volume pot. Tone pots usually have a linear taper to give a smoother range of control. Some manufacturers make a "one size fits all" audio taper pot which gives acceptable results when used for tone or volume.

By the nature of the circuit used, a tone control will always filter off some high frequencies even when turned fully clockwise, and indeed many players who find that they never touch their tone controls will disconnect them to add a bit of extra "sparkle" to their sound.

Source
#3
Thanks.

I may be asking the same question again, so just skip it if that is the case.
I think the question is more a basic question about electrical flow.
And I am looking for an apt metaphor to describe it.

We understood, although functionally it was probably flawed, the Jazz Bass
Pickup:Volume:Volume:Tone:Jack
The signal flows from pot to pot until it exits the jack.

Let's use a P Bass as our other example. Using what we know from the JB we would expect to see
Pickup:Volume:Tone:Jack instead it is Pickup:Volume;Jack
Tone

Okay, now that we see this, why would it not be wired
Pickup:Tone:Volume:Jack

I am not an electrical engineer and really know precious little about why these things work, I just follow the directions and know enough to do a little home wiring safely. Would it be correct to say that the pots function as gates that decide how much or what frequency is allow to flow to the ground?
#4
It doesn't matter in what order the tone pot and cap are connected to the rest of the circuit. It just needs to be connected in parallel with the output, so it can cut high frequencies to ground. Potentiometers are variable resistors. Resistors RESIST the flow of electrical current. Capacitors, depending on value, pass only higher frequencies. So together, the pot and cap form a filter. Depending on the resistor's value (pot position), more or less of the signal's higher frequencies will be routed to ground.

Go to this page and read up: https://www.ultimate-guitar.com/forum/showthread.php?t=547959