Simple question about tone capacitor

[joao2013]

Hi!

I've researched a bit about tone caps but there's a doubt I cant seem to get the answer to anywhere.

My fender p-bass clone has a passive split pickup and a .068mfd on the tone bleed. (also 250k pots for both tone and volume)
From what I've read, if the tone pot is full on, it doesn't matter if I have a .047 or a .068.

But my question is: Somewhere within the range of my tone pot using a .068 cap, can I find the exact same tone that I have when using a .047 cap with the tone pot all the way down?

In Other words, does the .068 cap give me the same sound that a .047 cap would, but with an extra lower range?

Thanks!

PS: I've been following this forum for a while, but only now I've registered

 

[megafiddle]

The cap value determines which frequencies are affected; the pot setting affects
how much those frequencies are affected. So no, it wouldn't be the same.

In one case the frequencies would fall off more gradually, but would begin falling off at
a lower frequency. In the other case, the frequencies would fall off faster, but begin
falling off at a higher frequency. Also, with the control at '0", any resonant peak would
be at maximum.

Probably best to simply try it. You can tack solder a couple wires inside the bass to the
points where the tone cap would connect, and extend them out from under the lower
edge of the pickgaurd. Then just tack solder each of the caps onto the wire ends and
try them out.

 

[SGD Lutherie]

From what I've read, if the tone pot is full on, it doesn't matter if I have a .047 or a .068.

This is true.

But my question is: Somewhere within the range of my tone pot using a .068 cap, can I find the exact same tone that I have when using a .047 cap with the tone pot all the way down?

No. The larger value cap will cut at a lower frequency point.

 

[dannylectro]

The cap value determines which frequencies are affected; the pot setting affects
how much those frequencies are affected. So no, it wouldn't be the same.

In one case the frequencies would fall off more gradually, but would begin falling off at
a lower frequency. In the other case, the frequencies would fall off faster, but begin
falling off at a higher frequency. Also, with the control at '0", any resonant peak would
be at maximum.

Probably best to simply try it. You can tack solder a couple wires inside the bass to the
points where the tone cap would connect, and extend them out from under the lower
edge of the pickgaurd. Then just tack solder each of the caps onto the wire ends and
try them out.

+1

That's a good idea.

 

[joao2013]

The cap value determines which frequencies are affected; the pot setting affects
how much those frequencies are affected..

Thanks! Thats plain and simple to understand!

A site got me confused because after talking about cutoff points and showing some graphs it said that the tone pot would affect where the cutoff point would be, and that it would be almost the same as a variable cap value... can't seem to find it again.

I feel the need to cut some higher frequencies, but my tone control muds everything up... I'll try the sugested method to choose a cap.

 

[Stealth]

A cool trick someone linked to long ago was to find a piece of cardboard and take several different capacitors. Punch small holes through the cardboard so you can push the capacitor legs through them, and put an alligator clip on each leg so you can connect to each capacitor individually.

As megafiddle said, pull up a pair of wires from the points where the capacitors would be and have them extend from under the pickguard - you can then connect the wires to each capacitor's alligator switch and quickly change among them to see which cut-off frequency compliments your bass best.

 

[khutch]

But my question is: Somewhere within the range of my tone pot using a .068 cap, can I find the exact same tone that I have when using a .047 cap with the tone pot all the way down?

In Other words, does the .068 cap give me the same sound that a .047 cap would, but with an extra lower range?

Not exactly, but sorta. When the tone pot is set to a high value the tone pot resistance and the pickup inductance/resistance form a first order low pass filter with a variable cutoff frequency set by the tone pot resistance. When the tone pot is set to a low value the pickup inductance and tone capacitor form a second order low pass filter with a fixed frequency set by their values and a damping factor set by the pickup resistance and tone pot resistance. And there is a gray area inbetween these two operating regimes. Attached below is a tone pot resistance and frequency sweep of a typical pickup with 0.047uF and 0.068uF tone capacitors (47nF and 68nF for those who dislike extraneous zeros ). Over much of the range of the tone pot the two cap values give you sensibly equal results. As you approach the minimum tone pot value they diverge but it depends on your tastes as to whether or not the larger cap is close enough to the smaller to give you the same results in the gray area plus a little more range.

Ken

 

[oldleftybass]

"Simple question about tone capacitor"

That's fine, as long as you understand that around here there will be no simple answers to that question.

 

[SGD Lutherie]

Over much of the range of the tone pot the two cap values give you sensibly equal results.

Great graph. That shows that until you get past the point on the tone pot where the impedance of the cap takes over from the resistance of the pot, you have more-or-less the same roll off. Then the cap takes over and you have the different curves.

An easy solution is to use a push/pull tone pot to switch between both caps.