Tone Pot Capacitors question

[iiipopes]

Late to the zombie thread: all the above. Please don't purchase paper-oil capacitors because the oil dries out and the value of the capacitor shifts. And to concur with the above: any good quality reputable capacitor will work. Go for ones with a lesser voltage rating because they are usually physically smaller, meaning they will actually fit in the control cavity where others may not.

 

[markanini]

I'd add if always have your tone control at 10 try some smaller value pots like .01uF down to .001uF, the tone pot will work more like a mid coloration knob. Useful for getting a P-ish tone from a J neck for instance, or for some extra grit when going in to a distortion pedal.

 

[iiipopes]

I'd add if always have your tone control at 10 try some smaller value pots like .01uF down to .001uF, the tone pot will work more like a mid coloration knob. Useful for getting a P-ish tone from a J neck for instance, or for some extra grit when going in to a distortion pedal.

This is exactly what Fender did with MusicMaster basses in the '70's. They had two capacitors: one .022 hardwired to ground on the tone knob, and the other standard .047 (or .05 at that time) as part of the tone circuit with the pot.

Pics of Musicmaster Electronics????

 

[micguy]

OK nobody here has covered this:

Ceramic caps (used in a lot of basses) can have several different kinds of dielectrics. In the capacitance range we're talking about here, it's doubtful you'll ever find an npo or cog dielectric capacitor. The bad news is that the other dielectrics lose their characteristics over time - your capacitor changes value (goes down) over time. If you're 60's Fender sounds better (or worse) today than when it was made, it may not be the wood.

Film capacitors don't do this. There is a valid (measurable) reason for caring about the type of capacitor you put in a bass.

I design circuits for a living - I'm not guessing, I know this stuff.

 

[jesterbass]

OK nobody here has covered this:

Ceramic caps (used in a lot of basses) can have several different kinds of dielectrics. In the capacitance range we're talking about here, it's doubtful you'll ever find an npo or cog dielectric capacitor. The bad news is that the other dielectrics lose their characteristics over time - your capacitor changes value (goes down) over time. If you're 60's Fender sounds better (or worse) today than when it was made, it may not be the wood.

Film capacitors don't do this. There is a valid (measurable) reason for caring about the type of capacitor you put in a bass.

I design circuits for a living - I'm not guessing, I know this stuff.

I wonder if you can approximately answer this:

Let's say I have a 0.47μF cap and I use either a 250KΩ or a 500ΚΩ tone pot. With the pot set to 10, there will be a little more treble with the 500KΩ than with the 250KΩ. Let's call that difference A. Now, let's use a 250KΩ tone pot but with either a 0.33μF or a 0.47μF cap. Again with the pot at 10, there will be more treble with the 0.33μF cap. Let's call that difference Β. What I'm getting at is how much bigger (or smaller) is A compared to B. I am only interested in the full on tone setting, and can't have no load pots or cutoff switches.

Basically I am forced to use a 250KΩ pot and I would like to know if I can mitigate the loss of treble compared to a 500KΩ by using a lower value cap. I can live with small amounts of treble attenuation from my tone pot, but I can't afford even a slight dulling of my passive humbuckers at maximum tone position.

If anyone else can chime in, I'd be happy to read your input

 

[micguy]

26535581[/URL], member: 91813"]I wonder if you can approximately answer this:

Let's say I have a 0.47μF cap and I use either a 250KΩ or a 500ΚΩ tone pot. With the pot set to 10, there will be a little more treble with the 500KΩ than with the 250KΩ. Let's call that difference A. Now, let's use a 250KΩ tone pot but with either a 0.33μF or a 0.47μF cap. Again with the pot at 10, there will be more treble with the 0.33μF cap. Let's call that difference Β. What I'm getting at is how much bigger (or smaller) is A compared to B. I am only interested in the full on tone setting, and can't have no load pots or cutoff switches.

Basically I am forced to use a 250KΩ pot and I would like to know if I can mitigate the loss of treble compared to a 500KΩ by using a lower value cap. I can live with small amounts of treble attenuation from my tone pot, but I can't afford even a slight dulling of my passive humbuckers at maximum tone position.

If anyone else can chime in, I'd be happy to read your input

With the tone pot at or near max, the pot value is what’s determining your tone. The normal value for the capacitor is .047 uF (not .47 uF), but with either value of pot at max, you can change the cap from .01 uF to 1 uF (literally 100 x the value), and you will not hear a difference from changing the capacitor value.

The capacitor value matters near the bottom of the pot range, but not near the top. Your suggested mitigation of a different pot value by changing the cap value? - nope, that won’t work. Sorry, tone controls on guitars and basses work the way they do, which isn’t the way most folks think they do.

 

[JayGunn]

Here's another way to maximize your brightness, outside the box, i.e. the control cavity:

If you change from a 20' cord to a 10' cord of the same model you will definitely hear more treble. That's because the capacitance of the cable will be lower so the resonant peak of the pickup will be higher frequency. (Of course if you can push that peak too high either you won't be able to hear it or your rig won't be able to reproduce it. This affects people who experiment with low impedance pickups.)

For a 'normal' passive bass cutting your cord capacitance in half could e.g. mean the difference between a 2.x kHz peak and a 4.x kHz peak, clearly audible.

Since I happen to have 2 cheap Asian capacitance meters (that agree with each other perfectly so I assume they are right) I can measure my cords. I have a 10' cord with about 360pF, (2) different 20' cords at about 650pF each and another 20' cord at over 1100pF. That 3rd one never gets used--too dull for me. Oddly the dull one was the most expensive.

Worth experimenting? HTH

 

[jesterbass]

With the tone pot at or near max, the pot value is what’s determining your tone. The normal value for the capacitor is .047 uF (not .47 uF), but with either value of pot at max, you can change the cap from .01 uF to 1 uF (literally 100 x the value), and you will not hear a difference from changing the capacitor value.

The capacitor value matters near the bottom of the pot range, but not near the top. Your suggested mitigation of a different pot value by changing the cap value? - nope, that won’t work. Sorry, tone controls on guitars and basses work the way they do, which isn’t the way most folks think they do.

I was thinking about this again... What would the effect be of adding a fixed series resistance of 250KΩ to the A250KΩ potentiometer? It should sound like a 500KΩ pot when maxed, given that, as you said, at 10 position it's the resistance that matters. But I can't work it out in my head, how such an arrangement will work in practice, under my hand and into my ears.

 

[jesterbass]

Here's another way to maximize your brightness, outside the box, i.e. the control cavity:

If you change from a 20' cord to a 10' cord of the same model you will definitely hear more treble. That's because the capacitance of the cable will be lower so the resonant peak of the pickup will be higher frequency. (Of course if you can push that peak too high either you won't be able to hear it or your rig won't be able to reproduce it. This affects people who experiment with low impedance pickups.)

For a 'normal' passive bass cutting your cord capacitance in half could e.g. mean the difference between a 2.x kHz peak and a 4.x kHz peak, clearly audible.

Since I happen to have 2 cheap Asian capacitance meters (that agree with each other perfectly so I assume they are right) I can measure my cords. I have a 10' cord with about 360pF, (2) different 20' cords at about 650pF each and another 20' cord at over 1100pF. That 3rd one never gets used--too dull for me. Oddly the dull one was the most expensive.

Worth experimenting? HTH

All this just makes me think that a minimal onboard buffer at the output of your passive bass would be a good idea.

 

[micguy]

I was thinking about this again... What would the effect be of adding a fixed series resistance of 250KΩ to the A250KΩ potentiometer? It should sound like a 500KΩ pot when maxed, given that, as you said, at 10 position it's the resistance that matters. But I can't work it out in my head, how such an arrangement will work in practice, under my hand and into my ears.

if you add it in series with the ground leg, yes, it will sound like a 500k pot at full volume, and you won’t be able to turn the volume down past -6dB.

 

[jesterbass]

if you add it in series with the ground leg, yes, it will sound like a 500k pot at full volume, and you won’t be able to turn the volume down past -6dB.

I must be getting something wrong. You seem to be describing a volume control. I was referring to a 250KΩ tone control. How would that work out? Luckily, the volume pot will be 500KΩ, linear.

 

[micguy]

I must be getting something wrong. You seem to be describing a volume control. I was referring to a 250KΩ tone control. How would that work out? Luckily, the volume pot will be 500KΩ, linear.

OK, you’ll have a tone control that does very little.

 

[jesterbass]

OK, you’ll have a tone control that does very little.

Would a higher capacity cap mitigate that?

 

[micguy]

Would a higher capacity cap mitigate that?

Not a bit. You could short the cap (making it an infinite capacitor in essence), and it’ll sound the same.