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Humbucker Question


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I'm working on making a home-made pickup. I think I'd prefer for it to be humbucking.

Anyway, I already got a prototype made! And it does indeed work! (It sends sound to the amplifier. Doesn't sound too bad, either!)

The question is with humbucking. I've verified that it does cancel some hum, but there's always quite a lot of electrical noise.

This is what it sounds like.

To explain what's going on there, I'm flipping the two pickups back and forth, so it goes back and forth between being hum-canceling and not hum-canceling. When it's hum-canceling, you still hear a fuzzy noise, but when they're not hum-canceling, there's an extra low pitched hum on top of that. (There's also a couple of bumps when I knocked something, unrelated to electrical noise).

Right now, when I made that recording, the circuit was just made with alligator clips. Does the extra noise sound like it's something that could be fixed with a permanent soldered circuit, and maybe some shielding? Or is it a sign that my homemade pickups just won't ever buck hum correctly?

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You have not told us if that pickup is mounted in a guitar…

Anyway, I think that if you mount this pickup and hook it up, taking care to connect the ground to the bridge/strings you will probably lessen the high pitch hiss. So, yeah, you will probably benefit from making a real installation, including shielding and ground connections. The 50/60 Hz hum you hear (low pitched) is very normal for what you are doing. It is perfectly normal.

Now we only need to hear the pickup being played :D

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Thanks. It'll be a while before I get a finished (non-prototype) pickup made, which is why I wanted to know if I was at least on the right track. And, yeah, the thing wasn't connected to a guitar; the cords were just kind of hanging in space.

As for grounding the bridge, that's another question I have. I've seen floyd rose bridges grounded, and it looks pretty easy, since it's easy to have a ground wire go to the routed area in the back.

But for this guitar I'm planning, I have a fixed bridge, with strings through body, through the bridge. I'm not sure -- is there a standard way of hooking a ground wire to that?

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Sure. Drill a hole through the control cavity to the hole for the bridge post/bushing. Just use a bare (non-insulated) vire and the pressure from the bushing will get good enough contact.

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Okay. It's a flat bridge that just uses screws, not a tune-o-matic with posts, but I guess it works the same. I think maybe I could have the hole come in from the pickup route rather than the control cavity. It seems like then I could have the hole go in as a straight shot, so it'd be easier to line up.

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Sorry, my bad. Just let the bare wire be pinched between the wood and the bridge and you will be fine. That is the "Fender way".

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Just FYI, as I've seen a lot of confusion about humbuckers...

To get humbucking, you need the coils wired electrically out of phase. If you wind your coils in the same direction, this means you connect (e.g.) the start leads of the coils together and send the finish leads to the output jack. You also need the coils to be opposite magnetic polarity. These two kinds of out-of-phase add up to a signal that is in phase and hum that is out of phase.

Also, if your coils are not balanced (say one coil is 3k and the other 4k), you won't get as much hum cancelling. However, in my experience, unbalanced coils can make for an interesting sounding pickup, so it's not a bad thing if you don't mind a little hum.

At least, that's my understanding. It may be helpful to your project.

Good luck.

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Sorry, I don't think I explained what's going on very well.

I'm planning on making a pickup with individual humbucking coils for each string. This will take a while to do, so I wanted to test it as I went. I especially wanted to test them since the pickups are hand-wound. Most humbuckers are machine wound so the two coils would be identical. I do count the winds, so at least those are equal, and the resistances are basically equal, but of course I'm not gonna get perfectly tight, sequential winds like you could get with a machine. So, I wasn't sure how well it would humbuck under those circumstances.

After I made the first coil, I verified (by simply holding it up to another guitar) that it worked. Once I made two, I figured I could test if it was humbucking.

I first wired it up to not be humbucking (they were wound the same way, so the end of one coil went to the start of the next). And there was noise. Then I wired it to be humbucking. (this was just a prototype circuit, so I did that just by switching some alligator clips around). And it still made noise. And I couldn't tell if there was more or less hum one way or the other. It took too much time to change the connections for me to remember exactly how much hum there was the other way.

So, I came up with a new test. There is another way of switching the humbucking properties of a pair of coils, other than how you wind them or the order you connect them. You can flip one of them upside down relative to the other. A counterclockwise wind, for example, looks clockwise if you look at it from the other side, which is why this works.

It was easy for me to flip one upside down, because I just had them in a prototype circuit outside of a guitar.

So, that's what I'm doing in that sound file there. There's always noise either way, but there is another low frequency noise that comes and goes as I flip one of the coils back and forth. This verifies that SOME of the hum is canceled.

So, my question was, is the remaining noise always gonna be there, maybe because having hand-wound pickups makes it unlikely to be able to fully cancel hum, particularly the high frequency component? Or would I be able to expect that all to go away once everything is fully shielded and soldered? Because if I couldn't get rid of that noise, it would obviously save me a lot of time to just go with single coils.

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Not to nag, but just make sure you have opposite magnetic polarities for each coil in a humbucking pair.

I am not sure about flipping the coil. I'm trying to envision how that would create two coils that are electrically out of phase, which is what you need. The simplest thing is to wind them the same direction and wire them out of phase.

You're probably right about that, but for some reason I'm not sure.

I imagine a lot of the high freq buzz will disappear when you have everything wired in and shielded. I wouldn't worry about it right now. If you've spent this much time already building a prototype pickup, you might as well finish it and use it.

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Flipping the coil will reverse the phase. You will need to ensure that the magnets in each flipped reverse phased coil are opposite too of course...if you were to wind six coils all the same way with the same mag polarity, then flip alternate ones for instance, this would automatically ensure reverse phase and polarity! I did exactly this for a dual core bi-lateral sustainer driver recently and had a plan with the same technique for a six coil model...so, great minds, hey!@!!

alligator clips and such, even holding them in your hands will dramatically add noise to any pickup. Having neat short connections to shielded cable will tidy that all up. The bridge will need to be grounded just as suggested to of course, and noise will be less when your body grounds the strings which run over the pickup, and with strat types, under it to with the trem springs (oh leo you were so clever at times!).

There have been quite a few pickups in the past that have used individual coils but none that are common, really it is a bit debatable if this feature actually improves the sound over other hum canceling strategies. As well as the alternating coil idea, you may get more "throw" of the magnetic field by arranging three coils in the lower strings to be opposite magnetically and electrically to the three upper strings...similar to the two coils in a P-bass or z-pickup. However, one then might consider if it wouldn't be easier for similar effect, to simply make two coils as in these designs than sets of three working together.

There was a thread here recently of an idea of making six coils but each coil a different shape and size and arrangement...

th_BtmIsoOfAssem.jpg

The idea was buried in this thread...LINK

I am not sure at all how this was intended to work and obviously a very radical design, if each coil is different (a neat idea) it may well reduce the humcanceling effect. Also each coil will have vastly different resonant frequencies and characteristics, you may find something really interesting, you may not. Remember also with such designs that it really isn't simply six little pickups as there is a fair amount of cross talk between them as they are magnetically coupled pretty strongly by being so close to one another (the magnets are attracted or repelled from one another and so generate signals in adjoining coils to some extent).

Some of these ideas have been scoured over in the massive sustainer thread as such devices are very much like pickups in reverse. Other novel arrangements of pickup coils include mounting them side on to the strings. Good for you in trying to explore some uncharted waters, and top marks for including a sound, so much easier to answer..and look forward to hearing them in due course....

pete

Edited by psw
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