Stacked Pickup and Hum

[raygun85]

I recently tried my hand at making a stacked pickup...its sort of a stacked P-90 design. Both coils are wound around 5.5K ohms, the magnets are in between the top and bottom coil, poles are South-oriented. Overall output is about 11.1K ohms. I thought this would be a straight-forward job but I'm still having some hum. Its not as bad a as a true single-coil, but not as good as a true humbucker. Am I missing something here?

[copperheadroads]

You should try reversing the wires.it should be hum canceling

[Mark Hammer]

Copperhead is correct, but I gotta say that those wide flat P-90 coils are more hum sensitive from the get go. So if there is any mismatch between them, you may end up with more hum than you were expecting. Less than a non-HB version, but more than you would have thought.

[David Schwab]

Your bottom coil has to be reverse polarity as compared to the top. This puts them out of phase. You will not have any hum, but you will note that at 11k it will be very bright and thin sounding.

This is why stacked pickups are often wound to around 24k.

I made a stacked tele lead pickup that read 11.36k. I was expecting it to be a hot pickup, but it sounded like a vintage wound pickup, and might have had a little less output.

[raygun85]

Thanks for the responses, guys. I'm a frequent lurker here on the forum. I do have the coils electrically reversed and in series. I'm using the top coil's start wire as my "hot" and the two finish wires are soldered together, while the start wire of the bottom coil goes to ground. My bobbins are a tad taller than a typical P-90, hand made. I'm just not sure what I've done wrong...the coils may be a bit off but they couldn't be off by much. I'll throw the meter on them tomorrow to make sure and post the results. Thanks again,

[Mike Sulzer]

What about the cores (screws)? Do the two coils have similar amounts of steel?

Thanks for the responses, guys. I'm a frequent lurker here on the forum. I do have the coils electrically reversed and in series. I'm using the top coil's start wire as my "hot" and the two finish wires are soldered together, while the start wire of the bottom coil goes to ground. My bobbins are a tad taller than a typical P-90, hand made. I'm just not sure what I've done wrong...the coils may be a bit off but they couldn't be off by much. I'll throw the meter on them tomorrow to make sure and post the results. Thanks again,

[David Schwab]

Thanks for the responses, guys. I'm a frequent lurker here on the forum. I do have the coils electrically reversed and in series. I'm using the top coil's start wire as my "hot" and the two finish wires are soldered together, while the start wire of the bottom coil goes to ground. My bobbins are a tad taller than a typical P-90, hand made. I'm just not sure what I've done wrong...the coils may be a bit off but they couldn't be off by much. I'll throw the meter on them tomorrow to make sure and post the results. Thanks again,

Are both coils wound in the same direction? (they should be)

Have you accidentally flipped one over?

Try reversing the leads on one and see what you get.

[raygun85]

The screws go all the way down through the bottom of the lower coil. I suppose it's possible that I accidentally flipped one of the coils over. I always write "top" and "bottom" on their respective sides. Both coils are wound the same direction too. I'll play around with it some more. Thanks again.

[Mike Sulzer]

But screws have a head that is more massive than the shaft. So you have different amounts of steel in the two coils. This limits the hum cancellation, but I do not know if that is a big enough effect to account for what you are hearing. You might be able to get an idea by taking the screws out and listening. The hum in each coil should drop some, but if the hum with the two in series goes way down, then you will know this is the problem.

The screws go all the way down through the bottom of the lower coil.