Dumb Questions About Volume Pots

[DTrane]

why do lower resistance volume pots give pickup more bass?


Also, if you used a 250k pot and turn the volume down, it shouldn't it sound the same as 500k pot. Obviously, you wouldn't know exactly where its 500k.

Also, splitting the coils don't sound like a true single coil cuz it still uses 500k pot. Is there a way to wire up a circuit so its 250k split and 500k humbucker mode?

 

[Lewguitar]

Re: Dumb Questions About Volume Pots

I'll answer question number one: lower resistance pots don't give a pickup more bass. Instead, they allow treble to leak through the pot and disappear to ground. They don't give anything - they lose treble.

 

[the guy who invented fire]

Re: Dumb Questions About Volume Pots

As for question number 2 I assume you are talking about splitting a humbucker and the answer is a split humbucker doesn't sound like a single coil because it's not...it's half of a humbucker.

 

[uOpt]

Re: Dumb Questions About Volume Pots

The resistance lowers the amplitude of the resonance peak. It removing treble.

For the tone pot turning a 500 Kohm pot to where it reads 250 Kohm on an ohmmeter is the same thing as having 250 in the first place. In the volume pot it is not because you are in the middle of the slider.

 

[Rodney Gene]

Re: Dumb Questions About Volume Pots

why do lower resistance volume pots give pickup more bass?


Also, if you used a 250k pot and turn the volume down, it shouldn't it sound the same as 500k pot. Obviously, you wouldn't know exactly where its 500k.

Also, splitting the coils don't sound like a true single coil cuz it still uses 500k pot. Is there a way to wire up a circuit so its 250k split and 500k humbucker mode?

You have your understanding of pots backwards, hunt down a few links and just read up a bit.

To answer your 2nd question...(because it is a very cool mod) yes. Wiring a resistor between the hot and ground of the potentiometer using the middle lugs and any outside lugs of a DPDT push/pull pot can give you a reange of pot value (load values) or 250k/500k. Its another mod that isn't used enough in my opinion. With implementation you can find the perfect load for your guitar. For ease of use, I use a volume pedal in my chain as a load device, but a swutch is a cool mod. Cheers and respect, RG

 

[DTrane]

Re: Dumb Questions About Volume Pots

ok, why is there more treble bleed? Is there something going on with capacitance or inductance?

I need to research this. I thought it would be a simple answer.

 

[Artie]

Re: Dumb Questions About Volume Pots

ok, why is there more treble bleed? Is there something going on with capacitance or inductance?

I need to research this. I thought it would be a simple answer.

It is. But a simple experiment will provide your best answer. It's only a little bit of work, and can be easily undone after the test.
Understand that you aren't actually rolling off treble, but changing the pickups "load". The net affect is, a progressive loss of treble, and signal strength.

Mod your volume pot wiring to this:



It's best to use a 1M linear pot for this, but if you already have a 500k, that will work too. (A 250k pot won't work.)

Ultimately, you should now have this:



Here's what's happening: Your volume control will now always be full "up", but as you lower the pot, you'll be lowering the "load" the pickup sees rather than the actual volume going out to the jack. The advantage of a 1M linear pot is that it allows this experiment to show you what a 1M volume pot sounds like compared to a 500k and 250k, (and everything in between). A 500k pot will let you compare 500k to 250k, and anything lower.

Try it, and let us know what you find.

Artie

 

[uOpt]

Re: Dumb Questions About Volume Pots

ok, why is there more treble bleed? Is there something going on with capacitance or inductance?

I need to research this. I thought it would be a simple answer.

A passive guitar pickup is a circuit with a capacitance, inductance and a resistance. It forms a perfectly normal second-order low pass filter (LPF) with a resonance peak. There really isn't any difference between the LPF that the pickup "automatically makes" and constructing such a second-order LPF yourself.
http://www.electronics-tutorials.ws/filter/filter_2.html (jump to second order to see formulas)

Changing any of the electrical values changes either the frequency at which the resonance peak sits (which is also the cutoff frequency for the LPF) or the amplitude of the peak.

Putting on a load with a resistor (a lower value volume pot) lowers the amplitude of the resonance peak.

Putting on a load with a capacitor (e.g. your guitar cable) on the other hand changes the frequency of the resonance peak.

 

[uOpt]

Re: Dumb Questions About Volume Pots

There is also this but my usual disclaimer: the author has very nicely documented some factors that are obviously true and how to control them, however he then proceeded to go overboard and claim that no other factors exist. Still, the parts that show how the LPF reacts are obviously true if you experiment with them:
http://buildyourguitar.com/resources/lemme/

 

[DTrane]

Re: Dumb Questions About Volume Pots

just to be clear, on wiring without a tone circuit, changing the value of the volume pot affects tone?

yeah, I read about a blues musician swearing by extra long instrument cables. He said it was part of his tone.

 

[uOpt]

Re: Dumb Questions About Volume Pots

just to be clear, on wiring without a tone circuit, changing the value of the volume pot affects tone?

yeah, I read about a blues musician swearing by extra long instrument cables. He said it was part of his tone.

Yes, regardless of whether you have a tone pot or not both the value of the volume pot and the position you put it in (turn it down) affect the sound.

People who want "long" cables are idiots. What matters is the capacitance. The capacitance per meter is specified by the manufacturer of the cable material. You can have shorter cables with higher capacitance and vice versa. This kind of voodoo makes me quite mad. When you have a cable that sounds good to you you better measure the capacitance right now so that you can reproduce it later.


And this blah blah doesn't begin to address the problem that the input impedance of your first rig state influences the load on the passive pickups the same way as the volume pot. So for the same effective amplitude of the resonance peak you want different volume pot values in the same guitar depending on what amp you go into.