On Capacitors

[ORCRiST]

I found this over on the Fender forums, some good info with clear explanations regarding caps, what they do, and how
they influence tone.

A pickup is like a little generator, producing combinations of small AC currents at different frequencies (i.e. notes).

Capacitors pass current in proportion to the rate of voltage change, they will pass more current for faster-changing voltages (High freq) and less current for slower-changing voltages (low freq).

For tone control, a variable resistor tone pot is connected in series with a capacitor, and this circuit output is connected to ground. The circuit input taps off the hot signal, which is usually going thru the volume control to the output jack and on to the amp circuitry. The cap allows certain higher AC frequencies to pass more easily, in this case to travel to ground instead of to the amp, the amount depending on the setting of the pot (resistance).

This picture may be used as a representative (only) of what happens when a cap is used in a guitar tone circuit. As the value of the cap changes, the roll-off point (transition from flat to angle) changes.  Higher cap values (.047uf) allow an increased/wider range of higher frequencies to pass - to travel to ground, so the resultant tone tends to be warmer. Lower values (.022uf) move the roll-off point to the right, allowing a decreased/smaller range of higher freqs to be rolled off, so the resultant tone is brighter.

In the graph, .022uf could be the purple line, and .047uf the red. Everything to their right would be going to ground and so not heard. The pitch of the line would be determined by the tone pot. Even when a typical tone pot is all the way open, a small bit of signal still passes through.

By using different value caps, you can color your tone a bit. (the pot values also effect this some, as there is a difference in resistance vs. frequency too). On a side note, caps also enhance some of the frequencies left behind, which may tend to make them piercing/annoying.

ORCRiST

 

[Superlizard]

Checkout my "Tone Pot Caps Vid" thread down the page a bit... you get to hear 'em in action.