Bleeding cap

[Boneless]

Hi everyone,

just took my bass to a guitar technician, I told him that I kinda disliked the fact that the volume pots tended to cut off treble too much, and he said "I'll do what they do on Telecasters, I'll put a cap" (what I understood being a "bleeding cap").

Now, I have read bleeding caps aren't supposed to be effective on 500k pots (which is what I have on my bass, since it's got humbuckers):

[quote]For other pot values, you unfortunately can´t use the "cap only" method because it would kill the mid frequencies. For this, you will need a treble bleeding network with caps and resistors in parallel or in series, depending on the configuration.[/quote] source: [url="http://www.premierguitar.com/Magazine/Issue/2007/Feb/The_Telecaster_Mod_Guide.aspx"]http://www.premierguitar.com/Magazine/Issu..._Mod_Guide.aspx[/url]

so, I ask you, is the tech doing a good job?
Plus, do bleeding caps affect tone even when the volume pot is maxed?

Thanks

[Al Heeley]

I put a small treble bleed cap on most of my electric guitars but have never tried it on the Bass, not sure if the same rules and cap values will apply to the different frequencies. But for the sake of a 25 pence capacitor and 5 minutes with the soldering iron its worth giving it a quick try, and if it screws up the tone or the mids you can always desolder it. Note: at max vol, the cap should be more or less bypassed so tone would not change, the cap should only start acting as a treble bleed when the vol pot resistance becomes big enough.

[Boneless]

I read you can put a resistor parallel to the capacitor, for a "better" effect.
What would be the difference? I haven't really understood.
Plus, would you suggest me some values for resistors and caps (always considering I have humbuckers).

[Al Heeley]

This from a useful link on Project Guitar dot com.

"
The reason for having a resistor with the cap is as follows. The cap itself controls how much of the guitar's circuit puts highs to ground. The cap value also changes the frequencies to a small extent. Smaller caps allow more highs to remain in the circuit but makes the tone thinner as you roll off volume. If the cap value is too high, then as you roll down volume, you actually have a brighter tone lower on the volume than you did with the volume on 10.
The trick is to use whatever cap value is transparent. My favorite values are 680pf, 820pf and .001 or 1000pf. I use these values in my Humbucker guitars with 500k pots.
In my Strat's I Like using either Kinman's mod of using a 130k resistor in series with a .0012uF cap or Seymour Duncan's mod of using a 100k resistor in parallel with a .002uF cap.
The resistor with the cap controls how fast the cap is allowed to either send or not send highs to ground. To some extent, the resistor also changes the pot taper and it's resistance. I'm also told that the series components have less effect on the taper of the pot and that the series resistor is a more gradual effect on the cap. You'll have to let your ears decide on this one. Both mods work great and are transparent though.

Notice you'll always place the components on the 2 vol pot terminals away from the terminal that is grounded to the pot case for it to work.
Make your connections tight and neat and use a heat sink while soldering and heat shrink tubing anywhere you feel you might have components touching places. I have the components placed purposely so you can see where they mount on the pot.
The Tele had a .001 across it's volume control. Some Tele's actually used a 1 meg pot also. We are talking bright. On my Les Paul with Duncan Humbuckers in both neck and bridge positions I have found I like just a ceramic 820pf cap across the bridge volume control and a .001(1000pf) across the neck volume control. I Like .015 mfd caps across my tone pots and I use CTS 500K pots. I Only use this treble bleed mod on my 500k dual Humbucker Gibson guitars. "

Here's the link to the full article:
[url="http://www.projectguitar.com/tut/potm.htm"]http://www.projectguitar.com/tut/potm.htm[/url]

[Boneless]

Neat!
Thanks a lot!

EDIT: I was thinking, though, the cap on the tone pot affects tone even when the pot is maxed. Won't this be the case with the bleeding cap as well? I don't really want to lose the low end...

Edited January 4, 2009 by Boneless

[BOD2]

More information here ...

[url="http://www.projectguitar.com/tut/potm.htm"]http://www.projectguitar.com/tut/potm.htm[/url]

[url="http://www.ratcliffe.co.za/articles/volumepot2.shtml"]http://www.ratcliffe.co.za/articles/volumepot2.shtml[/url]

I've done the same mod on a guitar. It certainly works. There's no audible effect on the sound when the volume is up full but as yout turn the volume down it does not get "muddy".

[Boneless]

My concern is that, though, the bleeding cap may have some effect even when the volume is fully turned up (like with the tone control), since pots aren't "perfect" and some of the signal still goes through the cap.
With a bass, I fear that some of the "high pass filter" effect the bleeding cap has (since it's just basically a HPF) may actually affect the tone. On a guitar, it is more likely to not hear any difference with the volume turned up, since the frequency range of a guitar starts, I think, at around 100Hz o something like it , while with a bass, the loss of deep low end that MAY occur could affect the bass's tone I don't really have a bassy tone, it's more of a high-mid/treble rich kind of sound, but still...

[BOD2]

I can't find any information from anyone who has fitted one to a bass guitar and done a before/after test.

However, it is very easy to add a treble bleed capacitor, and even easier to remove it if you don't like the effect. I would say that the only way to find out for sure is to try it and see.

As for the frequency response of a bass, remember that the low "fundamental" notes of the bass will often not be accurately reproduced by your amp/speaker combination anyway. However this isn't actually a problem since as long as the higher order harmonics are present then the brain "fills in" the missing information -

[url="http://en.wikipedia.org/wiki/Missing_fundamental"]http://en.wikipedia.org/wiki/Missing_fundamental[/url]

What this means in practice is that a slight loss of very low frequencies may actually be totally unnoticed if the note played remains rich in higher order harmonics.

[Boneless]

Of course, but the thing is, I am a serious paranoid about my tone, I probably wouldn't be able to live knowing that there MIGHT be a loss of low end, and nothing I can do about it on the fly
I'd end up screaming and tearing the cap away while jumping up and down on my amp

I will probably do it on my own, I told to the guitar tech not to install it, but I feel safer to do it myself, with my amp and being able to compare the tone before and after

Edited January 5, 2009 by Boneless