Categories
DIY guitar

The Fender TBX:
A Cool 2-Band Tone Control

You can TELL it's Photoshopped! There's no TBX!
You can TELL it’s Photoshopped! There’s no TBX!

Thanks again to everyone who chimed in on the “What your favorite mod?” discussion. I got tons of great ideas from your comments.

Like this one, which I’ve been meaning to explore for ages: the Fender TBX tone control circuit, which appears in several Custom Shop instruments, notably the Clapton signature Strats. Like the G&L PTB circuit I’m so apeshit about, it’s a 2-band passive tone control — but one that sounds very different.

The PTB is a two-knob circuit that lets you siphon off highs, lows, or both. I’m agog at how well it works with humbuckers — you can get so many cool sounds by rolling off lows on the way to a fuzz, as heard here.

But TBX (it stand for “treble bass expander”) is a one-knob circuit, tbough that single knob rotates two stacked pots. The control has a center detente. Set here, it’s like a regular tone control, wide-open. Turn it counter-clockwise and highs vanish, per usual. (You could “tune” the roll-off frequency with various capacitors, though I went with the stock .022uF.) But when you rotate clockwise, the absence of lows makes glassy highs erupt.

The dual pot cut highs or lows.
The dual pot cut highs or lows.

Technically, it’s not a boost, but it sure feels like one. Dirk Wacker, my now-colleague at Premier Guitar, dissects the circuit far more capably than I can here. (And he goes way beyond in this subsequent article on TBX mods. Man, I have some catching up to do!) He makes a good case for replacing the stock resistor with another value, but I went with the original 82K to establish a point of reference. I’ll try his mod when I restring, and I’ll update you here.)

BTW, you need the Fender TBX kit for this project — it uses highly customized pots to work its magic, and a standard stacked pot won’t do. But it’s cheap: You can find the TBX kit, with the pot, hardware, and passive components, online for about $15.

I put it into the mongrel strat I’ve been using as my digital synth/looping guitar. I’d been using a Stellartone Tone Styler, a cool Vari-Tone variant that switches between multiple capacitors. I dig it, but it’s the old model which clicks, rather than fades, from setting to setting, and it requires a powerful twist of the wrist to go from maximum to minumum, which I do every time I grab an EBow. Since I hadn’t gotten around to replacing it with the smooth-action version, I figured I’d try the TBX.

And I’m glad I did. It’s a super-easy install, at least to the extent that any job that requires removing both strings and pickguard can be easy.And here’s how it sounds:

I’m going to keep this one around for awhile. You’re hearing it through an analog rig, obviously, but I want to find out whether that extra shot of highs does anything meaningful when playing digitally. I’d also like to experiment with different cap and resistor values.

And now I can’t help wondering whether this would sound cool with humbuckers. Anyone have any experience with that?