Coil Tapping a Humbucker

[ZeroCool7]

Hi,
"Coil Tapping"[not coil-splitting] a humbucker means you're lower its output correct? So, if i were to coil tap a high output 15~17k humbucker, then that would put it around 7.5~8.5k, maybe?
So, would that be the same a using a low output humbucker like a '59[~8k]?

Thanks!

[big_teee]

Hi,
"Coil Tapping"[not coil-splitting] a humbucker means you're lower its output correct? So, if i were to coil tap a high output 15~17k humbucker, then that would put it around 7.5~8.5k, maybe?
So, would that be the same a using a low output humbucker like a '59[~8k]?

Thanks!

The only accessible points to a humbucker is each individual coil.
So if boith coils of a humbucker combined in series is 16k, then one coil would probably be half that 8k.
So like you mentioned you could run either coil split to get 8k, but then you are running it in single coil, non hum canceling mode.
Now to tap the coil like you suggest would be required, when building and winding the coils for the pickup.
I've not heard of this on a humbucker. You would have to tap both coils and switch them both at once.
Single coils are tapped some. Seymour Duncan does this on some of their strat and tele coils.
In theory I can see this, but I think the coil tap split is a much easier and practical application, and practice.
Good Luck

[Mark Hammer]

1) There are very few pickups that permit literal coil-tapping, where the same coil is tapped after different numbers of turns (e.g., after 7000 or 9000 turns). What many refer to as "coil tapping" is really coil-cancellation, where only one of the coils in a dual-coil pickup is providing audio signal.

2) There are several changes that arise from cancelling one of the two coils. First, you lose all the hum-cancellation. Second, the inductance changes because you have only the one coil. Third, the output drops because you have fewer turns. That is reflected in DC resistance, to be sure, but do not interpret a halving of DCR as a literal halving of output. You'll experience something like a 25-30% drop in apparent level, but a big chunk of that will be from the elimination of a certain amount of bottom end.

3) What does not change is the sensing area. Cancel one of the coils on a PAF-style and you do nothing to the magnetic coupling of the slugs and adjustable polepieces; the sensing area is still between them. Same is true for a stacked humbucker. That's one of the reasons why dropping half the #turns doesn't result in half the output level.

I encourage you to look into the old Peavey T-60 tone circuit. This provides continuous panning between both coils and one of them. Very clever circuit peaveyt60.com

[Mike Sulzer]

1) There are very few pickups that permit literal coil-tapping, where the same coil is tapped after different numbers of turns (e.g., after 7000 or 9000 turns). What many refer to as "coil tapping" is really coil-cancellation, where only one of the coils in a dual-coil pickup is providing audio signal.

2) There are several changes that arise from cancelling one of the two coils. First, you lose all the hum-cancellation. Second, the inductance changes because you have only the one coil. Third, the output drops because you have fewer turns. That is reflected in DC resistance, to be sure, but do not interpret a halving of DCR as a literal halving of output. You'll experience something like a 25-30% drop in apparent level, but a big chunk of that will be from the elimination of a certain amount of bottom end.

3) What does not change is the sensing area. Cancel one of the coils on a PAF-style and you do nothing to the magnetic coupling of the slugs and adjustable polepieces; the sensing area is still between them. Same is true for a stacked humbucker. That's one of the reasons why dropping half the #turns doesn't result in half the output level.

I encourage you to look into the old Peavey T-60 tone circuit. This provides continuous panning between both coils and one of them. Very clever circuit peaveyt60.com

I think a humbucker has two sensing areas, one for each coil. When you remove one coil, you lose its output, which is about one half of the voltage. This is true independent of how well-coupled the slugs and pole pieces are, or if there is one sensing area or two. Actually, the circuit is not well-coupled magnetically; the relatively low permeability of the alnico magnet and the poor physical contact between the slugs and the magnet assures that.

[Mark Hammer]

Well, human hearing being what it is, it may well be that we are both correct: a) the output IS one half, and b) it doesn't sound like it.

I certainly won't dispute the imperfect nature of the magnetic coupling. But I will note that there are all manner of single coil pickups that essentially mimic the sensing properties of a one-coil PAF (e.g., the Epiphone New Yorker, and assorted Japanese pickups from the 60's), by having the polarity of the adjustable screws that stick out be the opposite of the top of the magnet running through the coil that is magnetically coupled to the base plate. And those suckers are beefy; much beefier than they would be if the same coil was simply sitting atop the same ceramic magnet, single-coil style.

The same comment could be levied about the P-90, where the sensing area is modified by having those bars underneath stick out to the side and edges of the coil.

Whatever twist and turn this discussion takes, I think we would both agree that a PAF-style humbucker with one coil cancelled does NOT sound like a single coil pickup. And not just because it uses slugs and a bar magnet instead of having the magnet run through the coil.

[kleuck]

a PAF-style humbucker with one coil cancelled does NOT sound like a single coil pickup. And not just because it uses slugs and a bar magnet instead of having the magnet run through the coil.

That's the point, i think most of the split-humbuckers are of no interest at all, though i heard some of the more recent ones are pretty good at this game -did not test these ones- but the at least "old-fashioned" DM or SD ones are just plain crap when splitted, don't expect to hear a Strat out of a splitted "59 clone", never.

[Mike Sulzer]

That's the point, i think most of the split-humbuckers are of no interest at all, though i heard some of the more recent ones are pretty good at this game -did not test these ones- but the at least "old-fashioned" DM or SD ones are just plain crap when splitted, don't expect to hear a Strat out of a splitted "59 clone", never.

Look first at the frequency response. There is no reason to expect the resonant frequency and Q of one coil of a humbucker with 500 K pots to be the same as a strat pickup with 250 K pots.

[big_teee]

Look first at the frequency response. There is no reason to expect the resonant frequency and Q of one coil of a humbucker with 500 K pots to be the same as a strat pickup with 250 K pots.

Another thing, the guitars are usually tonally different.
Your gonna have a hard time getting a Mahogany Les Paul to sound like a Alder Strat, even with strat single coil pickups in it!
I have most of my guitars tapped, and you can get some pretty good results with them IMO. It's pretty much a waste of time to tap a neck low wound humbucker to start with.
Later,

[Mike Sulzer]

That's the point, i think most of the split-humbuckers are of no interest at all, though i heard some of the more recent ones are pretty good at this game -did not test these ones- but the at least "old-fashioned" DM or SD ones are just plain crap when splitted, don't expect to hear a Strat out of a splitted "59 clone", never.

Look first at the frequency response. There is no reason to expect the resonant frequency and Q of one coil of a humbucker with 500 K pots to be the same as a strat pickup with 250 K pots.

[Mike Sulzer]

More on magnetic coupling between the two coils of a humbucker

Some years ago, I built, without thinking it through, a humbucker that was tightly coupled between the two coils. It used slugs in both coils with laminated transformer steel connecting the pairs of slugs. It hummed. Flux passing through the connecting pieces along their length, that is, perpendicular to the slugs and the long dimension of the coils, is passed into the slugs. (It is coupled, after all.) The resulting hum adds in phase. A humbucker relies on poor coupling between the coils in order to reject hum fields in that direction. In spite of what the Seth Lover patent says.

[Mark Hammer]

The old Fender humbuckers were, I gather much more like a pair of non-magnetically-coupled single-coils, than like a PAF. I used to have one on a DIY guitar back in the mid-70's but unfortunately ditched it without ever exploring the possibilities of coil-cancellation.

Does anyone know if they sounded more like a single coil when using one coil only?

[Mike Sulzer]

The old Fender humbuckers were, I gather much more like a pair of non-magnetically-coupled single-coils, than like a PAF. I used to have one on a DIY guitar back in the mid-70's but unfortunately ditched it without ever exploring the possibilities of coil-cancellation.

Does anyone know if they sounded more like a single coil when using one coil only?

Let's look at the possibilities.

Suppose that you took two strat pickups that sound "right", that is, have the right resonant frequency and Q for your taste. If you put them in series to make a humbucker, the inductance is doubled into the same cable cap. This will not lower the resonant frequency the full 29% you might expect; the pickup capacitance was in the original equation, and it has been lowered. But the freqiency might come down 20 percent. This makes a difference. So it is possible that the Fender humbuckers had a reduced number of turns on each coil to keep more of the Fender Sound. If you used one of them as a single coil, the resonance would go higher, which might sound less bright if it moved too high, or more bright if it stayed within the range of the guitar speaker. Hard to tell.

[Rick Turner]

Another trick is to overwind one coil, but use the extra windings only when in single coil mode so as not to lose so much output. It might also be interesting to play with a mechanical magnetic coupling switch that would close couple or decouple two coils. Something like a removable "keeper" on the bottom of the pickup bobbins, assuming that you've got magnets in the bobbins rather than permeable pole pieces.

So much to try, so little time...

[Mike Sulzer]

Another trick is to overwind one coil, but use the extra windings only when in single coil mode so as not to lose so much output. It might also be interesting to play with a mechanical magnetic coupling switch that would close couple or decouple two coils. Something like a removable "keeper" on the bottom of the pickup bobbins, assuming that you've got magnets in the bobbins rather than permeable pole pieces.

So much to try, so little time...

Why would you want to couple them together it it is going to make them hum?

A normal humbucker is not magnetically coupled to a significant degree because the permeability of Alnico is not very high (and ceramic is lower, I believe). The magnet magnetizes both slugs and screws, but it does not provide a significant path for the time varying flux from the vibrating string to pass from one coil to the other.

[Rick Turner]

Mike, you just have to try these things to find out. I love all the theory, but it has not told me much about tone other than being able to predict resonant frequency and Q, and that's just not enough for me. I have to try things and use my ears. I've found a lot of tone that isn't in the simple resonant bandpass filter model of pickup response. I know you don't see it that way, but I trust my ears more than I trust your theoretical knowledge...which I respect, as far as it goes. Your approach is useful, and it's not the entire picture.