Could someone please explain a capacitor conundrum and offer a solution?

guildguy516

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Could someone please explain why a tone control with a .047uF capacitor does not sound like a .005uF, .022uF, .033uF anywhere its sweep?

In other words, why doesn't a .047uF sound like a .033uF on seven or a .022uF on five? I have switched toned caps several times on my Tele because I like different values with either pickup and I keep going back and forth between values.

Does anyone have a solution for using two different caps in a standard Tele setup yet preserving the tone control?

Thank you
 

Peegoo

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It's because the rating of the cap sets the cutoff frequency in the signal. The cap combined with the pot on a tone control is very similar to a narrow band parametric EQ that cuts but doesn't boost.
 
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edvard

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^^ This, plus what you are asking for is a variable capacitor, which a pot and cap do not make.
Let me put it to you this way: When you put a 0.047µF cap on a 250k pot, it will make a low-pass filter with a "knee" right around 300Hz. Take that same circuit and throw on a 0.022µF cap on there, and the cutoff frequency moves to approximately 850Hz (give or take a few). When you turn the Tone knob down, you are lowering the volume of all frequencies above that cutoff. That is why two different caps won't sound like the other at different settings.
The situation you ask about would involve moving the cutoff frequency itself, which is only possible with a variable capacitor (of which, one sized to fit in a guitar would be in the lower picoFarad range; not good for guitar tone control) or a rotary switch that switches in different capacitors in each position, like the Stellartone "ToneStyler" or the Gibson Les Paul Recording "Decade" control.
 

moosie

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Caps don't have 'sweep'. Pots do.

There are two components, not one. The pot is variable resistance over it's sweep. The cap is fixed capacitance, that sees variable signal, depending on the pot sweep. The cap cutoff or threshold freq is not variable.

Imagine a garden hose, your thumb over the end controls the flow (the pot). You're spraying through a screen. When you move your thumb, more or less water flows, but the screen grid size doesn't change.
 

Peegoo

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One thing you can try is a sweepable midrange control. This employs an inductor and a cap on a pot and was sold as a kit for years by Torres; look online for "Torres midrange control schematic." This type of tone control is very useful. It's the same basic concept behind what Reverend calls the bass contour control. Although this type of filter is sweepable, it's not capable of extremes like a wah pedal. Hohner used the same idea in their top-line TE Professional range (Tele clone as played by Prince, etc.).

Yet another type is a two-band tone control (treble and bass) layout that uses two pots, as in the scheme used on the early G&L S500. Look:

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