Tbx Tone Control Wiring Diagram

TBX Wiring Explained for People Who Just Want It Working

The TBX tone circuit is one of those mods that sounds way more complicated than it actually is. Most people overthink the wiring because the diagrams look like spaghetti, but it really is just a capacitor, a pot, and a couple of resistors doing specific jobs. I spent about three hours last year debugging a Strat where the TBX was behaving erratically and the problem turned out to be a cold solder joint on one of the pickup selector switch lugs. Not the TBX circuit itself. The TBX worked fine once the switch connection was solid. Here is the straightforward version of how it works and what you need to do.

Tbx Tone Control Wiring Diagram

The core circuit uses one 500k linear or audio taper potentiometer, a capacitor between 0.01µF and 0.1µF depending on your taste, and it slots into the space normally occupied by the third tone pot on a Strat. The signal enters from the pickup selector switch, passes through the TBX pot, and exits to the volume pot. The capacitor is wired between the wiper and one outer lug of the pot, and the other outer lug goes to ground. That is basically it. Let me walk through it more carefully because there are a few details that matter if you want it to sound right and not just vaguely "there." Start with the pot. A 500k linear taper works well if you want even control across the range. An audio taper gives you more dramatic change early in the rotation, which some players prefer. The TBX pot itself usually comes with the capacitor already mounted inside it on the commercial versions, but if you are building it yourself, use a polypropylene or paper-in-oil capacitor. Ceramic disc caps sound harsh in this circuit. I learned that the hard way with a 0.022µF ceramic cap that made the guitar sound like a toy when the tone was rolled back.

The wiring sequence: the hot wire from the pickup selector switch (position 2 or 5 on a standard 5-way Strat) connects to one side of the TBX pot. The wiper goes to the volume pot input. The capacitor connects between the wiper and one outer lug, and the other outer lug goes to ground. Some builds add a second capacitor for treble bleed, but that is a separate decision. The default TBX circuit does not include treble bleed. The natural behavior is that rolling back the tone pot progressively removes high frequencies while also scooping mids, which is the whole point of the circuit. One thing most diagrams leave out is the interaction with the volume pot. The TBX circuit assumes a 250k or 500k volume pot following it. If you put a 1M pot after the TBX, the tone response changes significantly and not in a useful way. Stick to 250k or 500k on the volume pot. If you are using humbuckers, go 500k. Single coils, 250k is traditional but 500k works and gives you a bit more highs when the TBX is at full. Here is the practical installation process. Desolder the old third tone pot. Solder the TBX in its place, making sure the ground wire from the original pot goes to the correct lug on the new TBX. Double check that the hot signal from the pickup switch reaches the input lug. Then solder the output wire to the wiper and run it to the volume pot. This takes about 15 minutes if your soldering is decent. If your soldering is poor, budget 45 minutes and a magnifying lamp. You will need both.

I have seen several people try to use the TBX circuit with coil-split humbuckers and hit a wall. The TBX was designed for single-coil impedance ranges. With a humbucker at full output, the tone can get muddy when rolled back because the higher impedance pickup drives the capacitor circuit harder. The workaround is to drop the TBX cap value to 0.01µF or even 0.0082µF. This keeps the highs tighter and prevents the mids from collapsing too quickly. I use 0.01µF myself on a bridge humbucker and it sounds balanced across the whole range. At 0.047µF, which is the standard Strat value, the same humbucker sounds noticeably flubby when the TBX is at half. Another detail that trips people up is the switch position. If you wire the TBX to only activate on the middle positions of a 5-way switch, positions 1 and 5 will bypass it entirely. That means the neck and bridge pickups will sound normal while the middle positions get the TBX treatment. This is actually a useful configuration and is how many factory TBX installations are wired. You need a switching mechanism to route the signal either through the TBX or around it. A push-pull pot or a mini-toggle switch on the control cavity plate can handle this. ADPot with a built-in DPDT switch is the simplest implementation and takes about 10 minutes to install. If you are looking for a wiring diagram to follow, the standard reference is the Lollar TBX wiring diagram. It shows the exact lug connections and capacitor placement. Search for "Lollar TBX wiring diagram" and you will find a clear PDF. There is also the Dimarzio version, which is functionally identical but with slightly different component values. Both work. The Lollar diagram is the one I reference most because it is the original design.

One more thing that is not obvious: the TBX circuit adds about 2 to 3dB of signal loss when engaged at full. This is normal and happens because the capacitor and pot create a small voltage divider. It is not a problem for most amplifiers. If you are running a very clean amp with low gain, you might notice the drop. The fix is simply turning the volume pot up slightly or using a pickup with a bit more output. This is the trade-off for getting a tone control that actually does something interesting. If your guitar already has a active preamp or an onboard EQ, the TBX will interact with it in unpredictable ways. The circuit expects a passive signal path. Putting it after an active stage can cause peaking and oscillation at certain knob positions. I tested this accidentally on a project guitar with an Apollon preamp and got a nasty squeal at the halfway point of the TBX. Moving the TBX to before the preamp stage fixed it immediately. Just keep it in the passive section of your wiring.

What to Avoid

Do not use a potentiometer with a switch that is rated below 500k. The TBX circuit draws more current through the pot wiper than a standard tone pot, and a lower-rated component will wear out faster and introduce crackling. Do not skip the ground connection on the outer lug. If that lug is floating, the circuit becomes a random antenna and will pick up interference that makes the TBX sound worse than a standard tone cap. Do not use a value lower than 0.01µF unless you know exactly what you are doing. Anything below that and the circuit stops having a meaningful effect and just acts like a poorly wired tone pot. The TBX is worth doing if you want a tone control that actually shapes the sound in a useful way. It is not worth doing if you plan to run the guitar through a heavy effects chain and only ever use the volume knob. The circuit shines when you are playing clean or mildly driven and want the tone knob to do real work. That is where it earned its reputation.