Tone Control help, please...

[tylereot]

Here's the layout: Jazzmaster with a Roadhouse Jazz pickup in the neck, Roadhouse Humbucker at the bridge, individual tone controls for each.

I've got mojotone 250k pots for tones, and a .22cap on the jazzmaster and a .47cap on the humbucker.
Both have the same problem: as I roll off the tone, it hits a cliff.  It's almost an on-off tone control for both.

I'm thinking the solution is the pots, and have both 250k and 500k of what I expect to be a better pot to replace them with.
How would you rewire this to give me a controlable tone rolloff on each pickup?
thanks everyone!!

 

[line6man]

I would assume you mean 0.022uF and 0.047uF? The values mentioned will provide a very low frequency cutoff point.

In any case, when a tone control behaves as a switch, it is usually because the taper of the pot is not appropriate for use in that application. Which ever taper you have, try using the other.

 

[tylereot]

Thanks, Line6man, I was thinking the pots were the issue.  I've got just the parts, and will try it tomorrow.

 

[greywolf]

Audio taper pots and a treble bleed circuit are your friends

 

[tylereot]

I put in a pair of DiMarzio 250k tone pots, and a couple of sprague caps, 22uF and 47uF respectively. 
That absolutely fixed the tone 'cliff'.  It didn't give me quite the tone I had in my head, but I'll keep playing with a couple of different amps, and tone settings.
It's still wicked bright, and it helps to be able to shave a little off with the tone controls, now.
Thanks gents!

Um.. what's a treble bleed circuit?

 

[Cagey]

Um.. what's a treble bleed circuit?

See here.

It's a good mod. Easy to do, and costs almost nothing. I put them in as a matter of course any more.

 

[line6man]

I put in a pair of DiMarzio 250k tone pots, and a couple of sprague caps, 22uF and 47uF respectively. 
That absolutely fixed the tone 'cliff'.  It didn't give me quite the tone I had in my head, but I'll keep playing with a couple of different amps, and tone settings.
It's still wicked bright, and it helps to be able to shave a little off with the tone controls, now.
Thanks gents!

Um.. what's a treble bleed circuit?

Those capacitances are three orders of magnitude greater than they should be, for the given signal impedance.

 

[bagman67]

Which is to say, they should be .022 or .047 uF, not 22 or 47.  Are you using shorthand, or are you really using 22/47 uF parts?

 

[tylereot]

I'm a guitar player, not a friggin' electronic engineer....  :icon_tongue:
Yeah, they're .022uf and .047uf caps.  And they sound icepicky and brittle, now that I've worked with them a little bit.  I think the values are fine, but the tone isn't warm and vocal as it was before. 
For some reason, the output SEEMS higher, more assertive.
I think they're coming out tomorrow morning, and the old caps going back in.  We'll see how that goes.

 

[tylereot]

Cagey and Greywolf: That loss of treble with the turning down the volume is NOT a problem here.  That's a definite characteristic of my Gibson, and it's very useful, actually.  I certainly wouldn't want to eliminate that from either guitar.
The Jazzmaster is bright as hell in any volume setting.

 

[Jumble Jumble]

.033uF is a nice value for single coils, perhaps try that.

 

[tylereot]

.033uF is a nice value for single coils, perhaps try that.

Can you give me an idea how increasing the capacitance would change the sound?

 

[Jumble Jumble]

It means that as you roll the control down, a larger proportion of treble frequencies are rolled off. As in, the lowest frequency that disappears is lower than the lowest frequency rolled off if the capacitor was of a lower value.

 

[tylereot]

It means that as you roll the control down, a larger proportion of treble frequencies are rolled off. As in, the lowest frequency that disappears is lower than the lowest frequency rolled off if the capacitor was of a lower value.

I figured it would be as you said: just a stronger rolloff effect. 
It's already VERY rolled off when I turn the tone control all the way down, I'll probably never use even that much.
Playing it this morning, I'm liking it better.  Rehearsal this afternoon, I'll see how it blends with others.  Thanks for your help!

 

[tylereot]

Some interesting Youtube videos by this chap comparing capacitors with a simple gizmo with a pot and alligator clips.
My pal has drawers full of guitar caps, we should set up a few of 'em...
http://youtu.be/rR4maqK_IhQ

 

[Re-Pete]

If you are shooting to slightly alter the tone you are getting (you mention the Jazzmaster is trebly, for example) then changing out Caps is a good way to zero in on the tone you want. Trial & error but it will get you close to what you want.
An alternative I might suggest, if you are happy to trial this, is seeing how the sound is affected by a Bill Lawrence Q Filter.
I tried them with a pair of mini humbuckers & the resultant tone came across as quite hi-fi clear. My modus operandi is usually to shoot for a clean tone with the guitar then let the pedals & amps colour from there. Tone effect wise, the Q-Filter gives the impression of 'winding back the coils' off the pickup giving a clearer, lesser gain tone. You can couple the Q-Filter with caps & resistors to give you a targeted EQ tone control.
I'm not intending to spam you for the product, just offering up something I trialled and found an interesting option to the usual tone control.
If you are curious, head to the Wilde Gate forum for more detailed descriptions of what the Q-Filter does.