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Old 11-02-2007, 02:36 PM   #100
J Kennedy
Human being with feelings
 
Join Date: Sep 2006
Location: ocean mists
Posts: 858
Default Telecasters, Rickenbackers, Tone Controls, Cats

Capacitors, rolled layers of foil and a paper dielectric inbetween. No direct connection, but inductances are set up that let selective frequencies thru. The larger ones can hold a near lethal charge from a 9 volt transistor radio battery.

Larger the farad rating, the wider range of frequencies that are induced and passed on. Lower the values and less gets transmitted, with the lower frequencies being blocked with progressively smaller capacitance ratings. The useful range in a guitar for tone control or different filters will be usually between 0.1 and 0.0001 microfarads. Starting from 0.1, a lot of frequencies get passed thru. Using 0.0001, most of the low frequencies are blocked but the hi frequencies still get thru.

Tone controls use the capacitor, usually a 0.01 mcf to shunt the high frequencies to ground with the pot restricting how much can be sent to ground. Turning down the tone control opens the capacitor to ground and the sound gets dull. Turn tone to 10 and you have mainly isolated the filter from the circuit and the tone is brite. Here is where you can experiment with various values to change the nature of the tone control. 0.005 mcf to 0.001 give a punchy midrange. 0.1 mcf gives almost pure bass.

Get a bunch of cheap waxed capacitors (Radio Shack deluxe again) and just start experimenting.

Fender Telecasters have their signature twang partly from using a small capacitor, not to ground, but to bridge the two non-grounded prongs of the volume control. The small capacitor blocks lo frequency as the master volume is turned down but allows a path for the hi frequencies to phase back into the signal. (I think the bypass is 180 degrees out). This is why the sound gets more tinny as you turn the volume knob down. The Fender amps use the same principle with a capacitor on a switch across the volume control. This is what the brite switch is and how it works. Here is another area for stage amp modeling, by going in and installing or changing the volume bypass filter to different values.

Guys, correct me if I'm wrong, but one 0.01 mdf capacitor will flip the phase of what is passed thru 180 out. Series two 0.005 caps and you get the original 0.01 with the bypass back in phase with minimal damage. This has never been a problem in my experience regardless.

Experimenting with different capacitors across the guitar master volume knob opens up a lot of neat rolloff possibilities and also can be used to offset guitars that tend to lose treble as the volume is turned down. You can use a resistor in series with the capacitor across the volume control to moderate the amount of capacitance in the circuit. Use a test potentiometer in series to adjust the right amount of capacitor bleed and then replace with a fixed resistor close to the value you want. (Use the ones with the gold band convention for higher precision, just a few pennies more). Small "trimmers" may work if they are within range and fit under the pickguard as permanent hardware. Gibsons have an extra knob to play with in the Gibson mod, so a variable rolloff knob can be used very nicely.

Rickenbackers get their characteristic sound partly with filters also. There is a fixed capacitor in series with the bridge pickup, essentially filtering out most of the bass response. When this is mixed with the neck pickup, you end up with a resulting sound that is heavy on the hi end and low end but not a lot of middle. Downside to this is that the filter makes the bridge pickup weak in volume and you have to be careful blending in the neck pickup without blowing a speaker. I had my bridge pickup on a switch to override the filter when needed. This approach can get some awesome sounds out of about any guitar. It simply requires an inline series capacitor on the hot lead of the bridge pickup and a switch to bypass the capacitor. Each guitar is entirely unique and so the choice of capacitors to give the best sound will be different for each.

As far as tone controls and Telecaster filters, these can be auditioned without taking the guitar apart first. A metal box with two potentiometers, two 12 position rotary switches and a bunch of capacitors is a must have tool if you do much of this. In the box, have one pot connected to a rotary switch that selects several gradients of capacitor values (0.1 to 0.0001). Run the output of the rotary to ground (capacitor and pot in series). The pot will now allow you to test different values of the tone control. This pot is set up (minus the rotary) identical to your tone control in the guitar, just outside. On the second setup, wire the pot just like your guitar volume control. Use the rotary and second set of capacitors to shunt across the two ungrounded leads of the volume control. This will allow you to test different rolloff filters and get the best choice for the specific guitar.

Rickenbacker filters can’t be put in an external box since you are not globally affecting the signal. Got to get inside for that one.

Hmmm..Looking back, I was going to explain how Claw tuned his guitar to let you know if you were going to heaven or hell. I should wait on this and let him address the collective himself. He’s got a much better handle on the fine points.

I can tell how to keep cats from pissing on your car tires. You need one of the bigger capacitors. Smaller capacitors like inside the guitar resonate down but can’t hold much of a static charge across the dielectric. Items like a car ignition capacitor can hold a good jolt. If you have the neighborhood pets doing their thing on your tires, here’s how to put an abrupt stop to the practice. Don’t know what it is about tires and cats, but once they start, you’re a target for as long as you own the car or kill the cat.

Take the capacitor and short it across the car battery for about 10 seconds. Bend the lead carefully back so that it almost touches the metal case. Clip the capacitor case to the metal tire rim or hub cap at the lowest point. Come sundown, the cats will start to do their tire ritual and the capacitor will discharge, frying their pecker instantly. It doesn’t take long to modify behavior.

Let me know if any of the schematics are unclear or any clarification needed.

John K

Last edited by J Kennedy; 11-02-2007 at 10:06 PM.
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