Tone control question?

[bwanasonic]

I recently tried this wiring variation of the stock tele pot wiring.



It's just moving the connection from the tone control to the volume, from the outside lug to the wiper (and sans the bleed cap).

Some people like it for added overall brightness and less of a treble emphasis when the volume knob is rolled down. I kind of liked the way it made the neck pickup sound, but I found it seemed to reduce the effectiveness of the tone control. Aside from the function of the treble bleed cap, what exactly is going on that makes the difference between having the tone pot pre or post volume knob?

Kerry M

[bwanasonic]

still looking for info on this basic principle that I'm trying to understand...

Kerry M

[Nasse]

http://www.gitarrenelektronik.de/

Pickup-Geheimnisse -  ausgeplaudert (englische Version hier)

[bwanasonic]

http://www.gitarrenelektronik.de/

Pickup-Geheimnisse -  ausgeplaudert (englische Version hier)

Thanks, looks like some good info there - now I just have to work on my german! :wink: It's better than my finnish though - that's pretty much limited to "Mika Hakkinen, Kimi Raikkonen, Marcus Grönholm and Timo Rautiainen"...

Kerry M

[Mark Hammer]

Think of it as if the treble frequencies had a "preference".  In the figure on the left, the path to ground for treble through the bleed cap (tone control) is independent of the setting of the volume pot,  Indeed, as far as the tone contro is concerned, the volume pot is simply one big fixed resistor, and it essentially "ignores" the very existence of the volume pot wiper.

In the figure on the right, you need to think of it like one big volume pot that has TWO ground legs in parallel.  One of those ground legs is not particularly picky about what frequency content it bleeds to ground, and the other ground leg IS.  However, note that if the not-so-fussy ground leg is set to a resistance lower than the frequency-sensitive one is, the second one will not matter very much.

I recommend use of the absolutely elegant tone control found on tweed Fender amps.  This combines a bypass and treble cut into one.

You wire it up as follows.  The wiper of your tone control is tied to the input lug of the volume pot.  One outside lug of that tone pot goes to your treble bypass cap (which then goes to your volume wiper).  The other outside lug goes to a much larger treble cut cap, and to ground, as per usual.

In this way, when you rotate the pot in one direction the resistance to ground gets bigger and you have lkess treble bleed, at the same time as the bypass cap  becomes more effective.  Rotate the tone control the other way, and the bypass cap is gradually rendered ineffective (bigger resistance in series with it) as more treble is bled to ground.  Here is a schematic for it: http://www.kbapps.com/audio/schematics/tubeamps/fender/princeton5f2a.html

Note that the 1meg pot on the left is the volume control, and the 1meg pot on the right is the tone control.  The specific values you might want to use could be different, depending on what sorts of tonal changes appeal to you.  Many people eschew 1meg pots for single-coil guitars because they find them too "brittle-sounding".  This sort of tone control allows you to compensate for 1meg pots easily, OR derive the max treble preservation they permit when you want it.

You will note, that just like the way it works on an amp, if the volume control is up full, there is no treble *added* by the bypass cap, even though treble cut will still function.  This may seem kind of stupid, but of course, the "default" volume setting on a guitar is full, while the volume on an amp is generally set to less than full.  What this type of tone control WILL allow you to do, however, is turn the volume down a bit, and then decide how much treble compensation you want to keep or lose.

[bwanasonic]

Thanks Mark! Should there be some sort of *scaling* of the caps if I were to use 250k or 500k pots?

Kerry M