Modding a TBX Tone Control For High/Low Pass?

[christopher]

So I'm making an attempt to do the Phostenix mod for the TBX tone control and have the unit act as a high and low pass filter. I have a few questions:

What cap values do you use? I was thinking .022 for treble and .0022 for bass cut, but I don't know exactly how drastic that will make the bass cut.

Are the tapers on the TBX good for this? The 250k side is log and the 1meg side is ~log.

Here's a link to his site:

sites.google.com/site/phostenixwiringdiagrams/modified-tbx-tone-control

[reTrEaD]

The tapers are in the right direction. As far as the severity of the bass-cut, it's always rather modest and quite dependent upon the resistance of the volume control. A 250k volume control will allow a few more dB of bass cut than a 500k will.

22nF is a rather common choice.

Much information was discussed on a previous thread.
guitarnuts2.proboards.com/thread/7172/bass-cut-ptb-system

In that discussion, the treble-cut is a separate control and uses a 500k pot, but the bass cut information should be pertinent.

[christopher]

I've heard that the 1meg tone also allows for a more prominent bass cut. If any of y'all have experience with bass cuts, what I'm looking for is a bass cut that has about the same apparent effect as the treble cut. I don't want a night and day low pass but a subtle high pass is what I'm saying. What value would best work for this with a 500k volume, 1meg for the TBX pot, and .022 tone cap?

[JohnH]

Its hard to predict what will sound best, but Id expect a 2.2nF cap, or less, could be 1nF. Well worth setting up initially so you can test a few values.

Although I never tried it, it looks to me that Phostenix' idea is a better use of the TBX pot than the original.

[christopher]

That it is, the stock TBX is essentially a 82k pot with a transition to almost no-load that takes up half the pot. Don't ask me how the person that wired it thought it was a good idea. It's useless in it's stock form.