Question about playing with pot values.

[Goldtop75]

I currently run 500k pots for both volume and tone for my Les Paul. I seem to stick to my bridge tone on 5, while the rest are always on full. It allows my bridge pup to have rounder highs, a slightly fatter upper mid freq, and a sweeter overall tone.

If i want to change my pot value to maintain the same effect on full, would changing the bridge tone to 300k or 250k help? Do I need to change my cap value (currently at .22?) I know that will limit my dynamic range, but I'm just exploring ideas here.

Anyone know?

[SKATTERBRANE]

Yes, changing your bridge tone pot to a lower value will replicate a 500K tone pot turned down. If you MEASURE your 500K tone pot at "5", you will know exactly what value your new tone pot should be at "10". No need to mess with your cap.


Or you could glue a tab on your tone knob at "5" and then put a nail in your guitar so you can't turn the pot past "5".

[SKATTERBRANE]

But I am curious as to why you would want to take away the option of being able to make it brighter? It is very useful in the middle position to have this range to play with.

I know a lot of people want the perfect tone with the pots turned to 10, and I am not sure why. Is it because it is easier to turn the dial to its stop rather than to hunt for the setting if it gets disturbed? (maybe pots should have detents, rather than a smooth sweep?)

[Goldtop75]

Originally Posted by SKATTERBRANE

Or you could glue a tab on your tone knob at "5" and then put a nail in your guitar so you can't turn the pot past "5".

Hahaha!!!!! Yeah... currently, I just leave it on at 5. Instead of changing to a smaller pot, maybe I just change to a permanent resistor?

However, considering the pot values usually run full only when on "0" (meaning the resistance value is at 500k only when the knob is on "0"), wouldn't the "10" (hypothetically "0"-load, though we know it's not.) position be the same regardless of pot value? Unless my understanding of a potentiometer is really that rusty. (which is very possible)

Originally Posted by SKATTERBRANE

But I am curious as to why you would want to take away the option of being able to make it brighter? It is very useful in the middle position to have this range to play with.

No, I don't want to remove the option. I will definately keep that optional range because the tone is nicer in middle position when all pots are on full. I want to understand the wiring concept behind this matrix. Mainly explained in my response on your earlier point about no-load points of a potentiometer.

[dpgumby]

Originally Posted by Goldtop75

However, considering the pot values usually run full only when on "0" (meaning the resistance value is at 500k only when the knob is on "0"), wouldn't the "10" (hypothetically "0"-load, though we know it's not.) position be the same regardless of pot value? Unless my understanding of a potentiometer is really that rusty. (which is very possible)

Not correct! This is how the pots are used:
The volume pots in your guitar are used as "potential dividers," that is the pickup is connected across the fixed resistance of the pot (to the outer lugs) and the signal sent to the amp is picked up from the wiper ("slider" if you prefer, the centre lug), this output signal being a proportion of the total voltage produced across the fixed resistance according to the wiper position.

The pot in the tone circuit on the other hand, is just used as a variable resistor - only the wiper and one end of the fixed resistor are connected, so (e.g.) the wiper is connected to the signal from the pickup (either before or after the volume pot depending on whether you have "modern" or "50s" wiring, respectively) and then the cap is connected between one end of the fixed resistor (an outer lug) and ground. (Order of the components makes no difference, but the correct lug must be used or your tone will work backwards). The lower the resistance, the more of the treble component of the signal is coupled to ground (and therefore unavailable to the output). So the tone is brightest when the resistance is max. (500K) i.e. with your tone control on 10, and darkest on 0, with zero resistance.

If you are using audio taper pots for your tone controls (and you should be, linears are useless for tone) then when your tone is on 5, the actual resistance will be about 50K (for an idealised taper). I have metered a few pots and I would expect it to be more like 30K in reality.

If you changed your tone pot to 250K, you would just knock off a slight (but noticeable) bit of top edge at 10, and the same tone as you current "5" would probably be somewhere around 6 - 6.5. Wouldn't be worth it.

What you could do is put in a push pull pot and switch in a fixed resistor for your "5" tone, if you want to select that quickly and easily.

[SKATTERBRANE]

Thanks dpgumby

[Goldtop75]

Originally Posted by dpgumby

The pot in the tone circuit on the other hand, is just used as a variable resistor - only the wiper and one end of the fixed resistor are connected, so (e.g.) the wiper is connected to the signal from the pickup (either before or after the volume pot depending on whether you have "modern" or "50s" wiring, respectively) and then the cap is connected between one end of the fixed resistor (an outer lug) and ground. (Order of the components makes no difference, but the correct lug must be used or your tone will work backwards). The lower the resistance, the more of the treble component of the signal is coupled to ground (and therefore unavailable to the output). So the tone is brightest when the resistance is max. (500K) i.e. with your tone control on 10, and darkest on 0, with zero resistance.

A-Ha! Exactly the answer I was looking for! and I think you are the right person to answer my next question: Tone pot in a circuit = LPF? or limited HPF? If it were a LPF, then technically it means that when I turn the knobs, the low end would be affected instead right? Though I've heard the term LFP loosely thrown around, I have a sneaky feeling the tone pot is essentially a HPF circuit?

Originally Posted by dpgumby

If you changed your tone pot to 250K, you would just knock off a slight (but noticeable) bit of top edge at 10, and the same tone as you current "5" would probably be somewhere around 6 - 6.5. Wouldn't be worth it.

What you could do is put in a push pull pot and switch in a fixed resistor for your "5" tone, if you want to select that quickly and easily.

Probably easier for me just to turn the knob. I wonder if they sell 500k audio taper pots with a notch in the center like those TBX boost knobs on the Fender EC Strat?

[Raz59]

Only some high frequencies pass through capacitors. Hence 'high-pass filter'.
Conversely, their counterparts - inductors - only let some low frequencies pass through them. Hence 'low-pass filter'.

Keyword here is 'filter'. You're filtering some high frequencies to ground via a capacitor, so your tone control = HPF

[dpgumby]

Originally Posted by Raz59

Only some high frequencies pass through capacitors. Hence 'high-pass filter'.
Conversely, their counterparts - inductors - only let some low frequencies pass through them. Hence 'low-pass filter'.

Keyword here is 'filter'. You're filtering some high frequencies to ground via a capacitor, so your tone control = HPF

Yes....and no.

As you correctly say, the capacitor does allow high frequency signals to pass through, and acts as a block to low frequency signals. The higher the frequency, the less the signal is attenuated. Conversely, the lower the frequency, the more the signal is attenuated. At zero frequency (i.e. D.C.) the capacitor is effectively completely open circuit. And also as you say, an inductor acts in completely the opposite sense.

BUT when considering the filter circuit, the capacitor (or inductor) should not be considered in isolation, but as part of the circuit as a whole, and its effect on the output of the circuit is what dictates the filter type.

In the guitar circuit, the fixed resistance of the volume pot acts as the load across the pickup, and the output for the amp is taken from the voltage across this resistive load (from the pot wiper), with the proportion of that output being set by the volume pot setting.

Now if we were to put a capacitor in series with this load, high frequencies would be passed through the capacitor an consequently through the resistor (as they are in series) and low frequencies would be blocked. So the result as seen at the output would be a High Pass Filter.

If we put the capacitor in parallel (i.e. across) the resistive load, then the high frequency component of the signal will pass through the capacitor and not through the load, so are not available to the output. Conversely, the low frequencies are blocked and thus pass through the load so are available to the output. So this configuration gives a Low Pass Filter.

The guitar circuit is this latter configuration, so gives a Low Pass Filter. The guitar tone circuit also includes a variable resistor (the tone pot) so that the cut-off frequency of the filter can be adjusted. ("Cut-off frequency" is just a measure of the frequency at which the attenuation is at a certain level (3dB down on no attenuation = about 70%)) - frequencies above that are attenuated more, frequencies below are attenuated less).

[And an inductor would work in the opposite way: Inductor in series with the load = LPF, inductor in parallel with the load = HPF].

Hope my explanation makes sense!

[Raz59]

^
II
II

What he said!

[Mookakian]

A lower value tone pot will also give you a slightly more compressed feel to your signal, i have found that depending on the pickups tonal qualities this can be a good or bad thing, for example, on my "11.5k Handwound Zhang" a 250k tone pot was not a good match as the compression added was able to hide the lovely dynamics and tone the pup had before the swap.

However on a "16k machine wound Seymore duncan Jazz", a 250k T/pot is perfect IMHO. Its a bright sucker thats for sure, but the 250k brings it back down to earth and the added compression suits it perfectly, taming its sizzling tone.

Just something to keep in mind while testing

Good luck GT