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Good Capacitor for 1meg Tone Pot?

T

timleona

Nov 9, 2009
8
0
#1
I ordered a 1 meg tone pot for use with my Fender Aerodyne and my new Dimarzio Model J bridge pickup. Dimarzio recommended a 1 meg tone as something to try. I left the original 250 ohm volume pot and it sounds pretty good. The Model J has a nice punch to it without the hum.

First, what is the effect of switching to a 1 meg tone pot (I think under all that solder the original is a 250)?
Second, is there a best match of cap to the pot or is it more about how much high end tone comes out with the cap rating?

Thanks!
 
#2
A 1M tone pot is exactly the same as a 250K pot from the 0 ohm to 250K ohm range. Beyond that range from 250K to 1M, the capacitor is further removed from the circuit, resulting in a brighter tone.

The problem is, with such a high resistance, the pot can act more like an on/off switch, depending on the taper. There can be a large portion of the sweep in which you hear very little tonal difference, because the capacitor is more-or-less removed from the circuit.

If you want a brighter tone, it would probably be a better idea to get a 250K no-load pot, or add a bypass switch to you tone control.

As far as the capacitor value, it's the same as with any other pot value.
Capacitor values are largely a personal preference btw.
0.047uF is the standard for most basses, but you can try a 0.1uF cap if you want more cut, or a 0.022uF cap if you want less.
 
#3
timleona said:
I ordered a 1 meg tone pot for use with my Fender Aerodyne and my new Dimarzio Model J bridge pickup. Dimarzio recommended a 1 meg tone as something to try. I left the original 250 ohm volume pot and it sounds pretty good. The Model J has a nice punch to it without the hum.

First, what is the effect of switching to a 1 meg tone pot (I think under all that solder the original is a 250)?
Second, is there a best match of cap to the pot or is it more about how much high end tone comes out with the cap rating?

Thanks!
Click to expand...

The value of the tone pot determines how much of the capacitor rolloff is "dialed" in to the circuit. I'll make two points.

1. The value of the tone pot determines the range over which the tone changes. Just try the pot(s). For example you may find that a 1 meg pot gives you a tonal adjustment over the whole rotation. That would be good. On the other hand you may find that the your 1 meg tone pot does absolutely nothing for a good part of the rotation and then suddenly starts affecting the tone. In that case a part of the pot rotation is wasted. Bottom line: Put in the 1 meg pot and see where tone starts to change. Leave knob there and measure pot resistance. Then THAT is the value pot (or there abouts) you'd want to have for tone control over the whole range of the pot.

2. When going with a high meg pot like 1 meg. You want to make sure your tone capacitor does not have any leakage. The worst culprits for this are those flat ceramic disk capacitors. If you have one, you'll want to change it. The absolute best low-leakage caps are polystyrene, but any of the mylar or other "orange drop" types will be just fine. Since these caps are relatively cheap (unless purchased from guitar parts places) as others have suggested you may want to try a few different values of capacitance just for grins.
 
#5
I looked and the tone capacitor is a .047uF green thick rectangle. I guess I'm not really looking for a much brighter one as much as a clean punch with a non muddy depth so maybe the 1 meg idea isn't the right direction to go.

I did change the volume pot on the original Fender P-pickup from the original 250 to a 500 because I thought I understood that that would sharpen and brighten what I think is kind of muddy tone but it doesn't seem to have helped much. I Left the 250 on the Dimarzio J volume pot.

Maybe, since I like the response of the Dimarzio Model J where I really need to look is at replacing the P-pickup with something tighter.
 
#6
timleona said:
Second, is there a best match of cap to the pot or is it more about how much high end tone comes out with the cap rating?
Click to expand...

Experiment. Some different values of caps are really reallllly cheap at an electronic supply store. Try some different ones out and decide which one you like best.

Stick around .047μF more or less. Try down as low as .01μF (will cut highs at a higher frequency) or as high as .1μF (will cut highs at a lower frequency) and several values in between.

You're in a great position to do some testing and discover what you prefer. :)
 
#8
walterw said:
ok, i'm lost; what "leakage" are you even talking about?
Click to expand...

I'm assuming he's talking about the high leakage resistance characteristic of ceramic capacitors.

The effect is the same with all pot values, it's a question of the capacitor, not the tone pot.

And of course, for the record, I don't buy into the hype that certain capacitors sound better than others.

As far as I'm concerned, the only thing that matters is the tolerance/actual value.

Any differences in composition, leakage, ESR, ESL, whatever are all meaningless for this application.
 
#9
I decided to try the 1 meg pot but realized that the diameter of the Fender(CTS) pot thread that I ordered is wider than the "dime" volume pots that I got from Guitar Ctr( they didn't have a 1 meg pot). It's also a short shaft, as the body thickness is greater. Is there a good source for pots that are longer and "dime" sized for a smaller cavity? I've looked around and seem only to be finding the shorter models and the "quarter" sized base.
 
#10
timleona said:
I decided to try the 1 meg pot but realized that the diameter of the Fender(CTS) pot thread that I ordered is wider than the "dime" volume pots that I got from Guitar Ctr( they didn't have a 1 meg pot). It's also a short shaft, as the body thickness is greater. Is there a good source for pots that are longer and "dime" sized for a smaller cavity? I've looked around and seem only to be finding the shorter models and the "quarter" sized base.
Click to expand...

I don't believe I've ever seen long shaft mini pots, save for push/pulls.
 

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