ASK-HBS – Slight Loss in Output When Mixing Humbuckers

Question

Hi Humbucker Soup,

Could you offer me some guidance on an issue I found with the three pickups on my Les Paul-style guitar?

When dialing in the bridge and middle pickups, I noticed that when the volume of each is turned up to the max, I get a slight loss in overall volume output. I have a normal humbucker in the middle position and two mini humbuckers for the bridge and neck. The sound output for each pickup is fine when they are used separately. The slight loss in sound output is not thin like an out-of-phase issue. I have read that this could have something to do with impedance mismatch. Have you come across this in your work? If so, is there a sensible cure? I have used linear pots for the three volume controls and one tone control.

John

Answer

Hello John, and thanks for the great question. Two mini-humbuckers and a standard is an unusual configuration. I love it! My only knowledge of impedance mismatches in this context has to do with the old telephone system. Originally there were impedance mismatches in telecommunications because the wires in each town were of different lengths. This mismatching caused the phone company to put transformers on the poles to raise and standardize the impedance. However, the mismatch didn’t just cause a weak signal at the receiver end. It also created an echo and phase cancellation.

Even though the output of the standard humbucker likely differs from the mini-humbucker, people have been mixing even smaller output single coils with full-size humbuckers for years without problems, so while I’m not an expert on impedance mismatches, I think we can rule it out, at least for now.

Since the pickups are next to each other, I believe one of the following things is the most likely cause.

1. One of the pickups (the bridge) has incorrect wiring, and it’s out of phase. Volume loss can be a sign of frequencies canceling each other out even if it doesn’t sound out of phase. Three humbuckers are a lot of wires, and mistakes happen.
2. Your bridge pickup is upside down. The coils in your humbucker are in opposite directions. If the coil closest to your bridge is going clockwise, then the coil in your middle pickup closest to the bridge pickup must also be going clockwise, and the same for the neck pickup. This way, the coils go clockwise, counterclockwise, clockwise, counterclockwise, clockwise, counterclockwise. If one of the humbuckers were upside down, two coils in a row would be going in the same direction and causing problems. It’s easier than you might think to put a pickup in upside down.
3. The pickups are too close and too powerful. Three humbuckers are a lot of magnets and coils in close proximity, and there is a good chance that even if everything has the correct wiring, the magnetic fields are just too strong and are interfering with each other. This interference can cause unexpected behavior, including frequency cancelation and volume drop-off. There’s probably a reason we don’t see more three-humbucker guitars.

I blame the bridge pickup because there is no problem with the neck and middle pickup. For that same reason, I’m betting on option one or two, leaning heavily toward two. I’m sorry I couldn’t be of more help. If I had a wiring diagram, I might be able to tell you if something was wrong. I hope you get it worked out. I’d love to know how you solve it.

Thanks again for the question and for reading Humbucker Soup. Let us know if you have any more questions.

Follow-Up Question

Thanks again for your help. It’s really appreciated. Are you saying that I should treat each coil in my humbuckers, when testing them with a multimeter and metal bar, as if they were separate?

John

Answer

No, Once you have the humbucker wired correctly, you should have 1 HOT and 1 GROUND for both coils. You can use the same test you are using for individual coils and use it to test the entire humbucker. You can test all three of your humbuckers. If the reading is positive for one humbucker, it should be positive for all 3. If one of them is opposite the others, particularly if it’s the bridge you are having problems with, switch the hot and ground for the entire pickup.

Follow-Up Question

If so then I can follow what you are saying. Let me explain how far I have got. I can identify the wires of one coil that is north as black, positive and hot, and white negative. For the second south coil, I have red as positive and hot and green as negative. In this instance, if I connected the green and white wires would this make a complete humbucker?

Answer

Exactly, you are absolutely right!

Follow-Up Question

In this configuration, I could keep black as positive and hot and then the red would become the negative to ground.

Answer

Exactly right again. The HOT is the HOT from the North coil, and the GROUND is the HOT from the SOUTH coil.

Follow-Up Question

I’m not sure if this is right or not because the wiring diagram for this particular pickup shows black to ground, red and white linked and green as hot. I have contacted the supplier who confirms this is right. So I am totally confused right now!! Any input would be appreciated but I understand if you do not have the time for this.

Thanks

John

Answer

Yes, I can definitely see why you are confused. You can’t argue with a wiring diagram, especially after the manufacturer confirms it. I can’t explain why your results differ so much from the wiring diagram, and the only thing I can come up with is that it’s hard to read the value as your metal bar approaches the pickup consistently due to you using an analog meter. However, people used analog multimeters for decades before digital ones arrived, so it is doable. My advice is to sit with the pickup and the multimeter until your readings match the wiring diagram. You won’t be able to test the entire humbucker until your single-coil readings are working out.

I’m sorry you’re still having trouble, but you are doing everything right and are very close.

Keep us updated!