"Quieting the beast" questions

[Carl]

Hello all. I am currently attempting my first mod on my strat. I'm doing "Quieting the beast" in combination with "Mike Richardson's Strat Wiring." After diving in I have stumbled upon a few questions:
1. What is the purpose of the little capacitor on the tone pot?
2. What does each of the three poles on a pot do?
3. Are vol and tone pots exactly the same?
4. On "Quieting the Beast," why does shielded cable need to be used for the output jack?
Any help would be appreciated.

[StratLover]

Hey Carl, nice to have another fellow Texan amoungst us.
This is a link in GN1 to explain a little more about your questions:


1.Capacitors have a very useful property, the impedance (total resistance) of a capacitor varies with frequency. At high frequencies the impedance is low, while at low frequencies the impedance is quite high.Generally, the low end terminal and wiper are used in tone controls. The impedance (or total resistance) of a capacitor varies with frequency -- this is what makes them useful in tone circuits. At high frequencies the impedance is fairly low, while at lower frequencies the resistance approaches infinity. The higher the value of a capacitor the lower its impedance will be at a given frequency. Capacitors come in a huge range of values and are used for many things -- including to "filter" AC hum out of a power supply and so on. The capacitors used in guitars will generally be in the range of .001uf (for a "bypass" capacitor on a volume control) to 1uf (for an "isolation" capacitor to separate the signal return from a shield ground). Capacitors used for guitar tone controls run from about .01uf to .047uf. One must consider the value of the tone pot when selecting a capacitor to go with it. The higher the resistance of a tone pot, the higher the value of the capacitor must be to achieve the same tonal response.

2.A potentiometer ("pot") is simply a resistor with a third terminal which connects to a "wiper" which slides along the resistor, changing the resistance between the wiper terminal and the terminals at each end. Potentiometers are measured in ohms, as are fixed resistors. Most American made Strats use 250k pots for volume and tone (those with TBX use a ganged 5k and 1meg pot). Most American made Les Paul style guitars use 500k pots.

There are two main types of potentiometers, linear taper and audio (or log) taper. The latter are the kind used most often in guitars. Audio taper (or just "audio") pots are constructed so that the amount of resistance change per degree of shaft rotation varies from one end of the pot to the other. It's essential to use an audio taper pot for the volume control. The tone control could easily use a linear taper pot but the manufacturers have pretty much stuck to using the same part number as the volume control -- doubtless to reduce manufacturing inventories.

3.Often, one end terminal is "disregarded" by either not having anything attached or by being shorted directly to the wiper arm -- in these cases the pot is being used as a simple variable resistor (tone controls). In other cases, a signal is applied across the two "ends" of the pot and the wiper arm is connected to the next "stage" of a circuit -- thus, when the pot is turned, the amplitude of the signal "picked up" from the resistor is varied (volume controls).

4.Generally, the low end terminal and wiper are used in tone controls. For volume controls, the low end of the pot is attached to "negative" or "ground" and the high end of the pot is attached to the positive signal source and the wiper is attached to the positive side of the output jack.

Potentiometers are also rated for the power they can dissipate. However, the circuits in the guitar itself are of very low power and the rating is not important. A few amplifier circuits, though, require special pots.
5.By using the shielded wire you are contining on with the shielding process all the way to the input of your guitar and leaving NOTHING underneath the WHOLE pickguard UN-SHIELDED.

Hope this helps you out.

[Carl]

That clears up a lot of misunderstanding! Thanks for your help.

[StratLover]

My pleasure Carl ! ;D

"Good Luck", and if you need anything else, LET US ALL KNOW.