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Coil-swapping pickup - feasible?

9/2/2002 7:17 PM
Mark Hammer	Coil-swapping pickup - feasible? Many years ago, in conversation with the guys at Evans pickups, I suggested a design that I thought would be kinda nifty. Their response was that it probably would not work, although I never pursued it further. Now I'm thinking about it again and would like some input from you folks. In the best of all possible worlds, the user can have both single-coil ("Fender") and double coil ("Gibson") sound from the same pickup position. In past, the recommendation was to have coil cancelling in a traditional side-by-side humbucker. This produced two problems, though. The first was that one would lose hum-cancellation by dropping one coil. The other is that the smaller number of turns on the remaining coil would result in a noticably lower signal. Losing output and gaining noise did not seem like much of a win-win situation, but without available alternatives, we went for it. Years later, a number of folks had worked on, and produced, side-by-side dual-coil PUs that would fit in a SC space (the dual-rails type), and various types of "stacked" humbuckers that attempted to get a single coil timbre with dual-coil hum-reduction. Depending on who you speak to, these either worked or didn't. It occurred to me, that maybe what one needs is a triple-coil pickup - in a Gibson HB type housing - where the switch from HB to SC tone would involve keeping one coil constant and swapping the other two. Consider this arrangement... Inside the housing are a Kinman-type stacked humbucker and a shallower profile single coil. The polepieces are arranged so that the stacked unit has its polepieces opposite polarity to the shallow coil. The pickup is wired with the lower coil of the stacked pair and the shallow coil in parallel, and this combo in series with the upper coil on the stacked unit. A DPDT switch selects between the shallow coil or the lower coil on the stacked pair. In pinciple this gives you two kinds of humbucker, stacked and side by side. The loss of bass when you switch from side-by-side to stacked mode will still be there, though not as dramatic since the signal level may remain fairly similar. Unlike simple coil cancelling, you get to keep your hum-rejection. (An SPDT will cancel the musical aspect of the other coil but leave its' "antenna" properties intact, potentially yielding less hum-rejection, so a DPDT which truly lifts the coil out of circuit is preferred.) Now although it ought to work in principle, what I'm wondering is whether the placement of two independent sets of polepieces so close to each other will create the sort of magnetic nuisance you can't really get around. Opinions? Empirical findings?

9/2/2002 7:17 PM

Mark Hammer

Coil-swapping pickup - feasible?

Many years ago, in conversation with the guys at Evans pickups, I suggested a design that I thought would be kinda nifty. Their response was that it probably would not work, although I never pursued it further. Now I'm thinking about it again and would like some input from you folks.

In the best of all possible worlds, the user can have both single-coil ("Fender") and double coil ("Gibson") sound from the same pickup position. In past, the recommendation was to have coil cancelling in a traditional side-by-side humbucker. This produced two problems, though. The first was that one would lose hum-cancellation by dropping one coil. The other is that the smaller number of turns on the remaining coil would result in a noticably lower signal. Losing output and gaining noise did not seem like much of a win-win situation, but without available alternatives, we went for it.

Years later, a number of folks had worked on, and produced, side-by-side dual-coil PUs that would fit in a SC space (the dual-rails type), and various types of "stacked" humbuckers that attempted to get a single coil timbre with dual-coil hum-reduction. Depending on who you speak to, these either worked or didn't.

It occurred to me, that maybe what one needs is a triple-coil pickup - in a Gibson HB type housing - where the switch from HB to SC tone would involve keeping one coil constant and swapping the other two.

Consider this arrangement...

Inside the housing are a Kinman-type stacked humbucker and a shallower profile single coil. The polepieces are arranged so that the stacked unit has its polepieces opposite polarity to the shallow coil. The pickup is wired with the lower coil of the stacked pair and the shallow coil in parallel, and this combo in series with the upper coil on the stacked unit. A DPDT switch selects between the shallow coil or the lower coil on the stacked pair.

In pinciple this gives you two kinds of humbucker, stacked and side by side. The loss of bass when you switch from side-by-side to stacked mode will still be there, though not as dramatic since the signal level may remain fairly similar. Unlike simple coil cancelling, you get to keep your hum-rejection. (An SPDT will cancel the musical aspect of the other coil but leave its' "antenna" properties intact, potentially yielding less hum-rejection, so a DPDT which truly lifts the coil out of circuit is preferred.)

Now although it ought to work in principle, what I'm wondering is whether the placement of two independent sets of polepieces so close to each other will create the sort of magnetic nuisance you can't really get around.

Opinions? Empirical findings?

9/2/2002 7:49 PM
SK	As you noted, it should "work", but I'm not sure about doing it in a singlecoil size format. The main issue I see is matching the "3rd" coil to one of the two in the stack. If I understand the design correctly, it would require using coils of different guage wire (oop's; patented...)or, there will be a more significant change in output between the stack combo and the side by side combo (probably can get around that by using both coils "active" in the stack). Also, having the polepieces that close together is a significant compromise for "humbucker tone", IMO. I don't believe having the magnets further apart as in a standard humbucker affects the "singlecoil tone" as much as the other affects "humbucker tone", but either way it will have an effect. My "reference" for this is the work in designing humbuckers meant to be cut to singlecoil as a major feature, and some experience working with singlecoil buckers (stack and side by side types).

9/2/2002 7:49 PM

As you noted, it should "work", but I'm not sure about doing it in a singlecoil size format. The main issue I see is matching the "3rd" coil to one of the two in the stack. If I understand the design correctly, it would require using coils of different guage wire (oop's; patented...)or, there will be a more significant change in output between the stack combo and the side by side combo (probably can get around that by using both coils "active" in the stack). Also, having the polepieces that close together is a significant compromise for "humbucker tone", IMO. I don't believe having the magnets further apart as in a standard humbucker affects the "singlecoil tone" as much as the other affects "humbucker tone", but either way it will have an effect.
My "reference" for this is the work in designing humbuckers meant to be cut to singlecoil as a major feature, and some experience working with singlecoil buckers (stack and side by side types).

9/2/2002 11:21 PM
Tony@Mastertone	Mark It will work but I think not to the level of satisfaction you would expect... as I have been doing this configuration for some time... although active... same principle. I first tried the 3 coils as you are proposing... but found it much simpler to just use two stacked coils side by side in parallel. Mainly due to switching noise through the circuit... Bear in mind I am doing this under active conditions though and have the luxury of using as many coils as I want without high freq signal loss, you do not being passive. Also I then found that the output voltage difference wasnt that fantastic, due to the two parallel pickups side by side... so I am about to start playing with different value inductive coils to compensate.. also don't forget mutual inductance where your live coil is being influenced by those extra 6 magnets sitting 1/2" away... Another consideration is magnets... a big part of the HB sound is the bar magnet... a big part of the Strat sound is the 6 rod magnets.. whether you can use a combination or not I haven't considered, you may get good results.. I realise this info may be of no help to you being active related but... can I suggest you take two normal single coils and mount them side by side... by switching one in and out you should be able to see the effects of the dead coil on the live one in relation to mutual inductance without spending many hours building this pickup to find mutual inductance kills it. I eventually came to the conclusion that by just changing the string aperature alone I could get the effects I needed to 'simulate' dual to single coil operation...hence the decision to use two stacked side by side coils.. Tone

9/2/2002 11:21 PM

Tony@Mastertone

Mark

It will work but I think not to the level of satisfaction you would expect... as I have been doing this configuration for some time... although active... same principle.

I first tried the 3 coils as you are proposing... but found it much simpler to just use two stacked coils side by side in parallel. Mainly due to switching noise through the circuit...

Bear in mind I am doing this under active conditions though and have the luxury of using as many coils as I want without high freq signal loss, you do not being passive.

Also I then found that the output voltage difference wasnt that fantastic, due to the two parallel pickups side by side... so I am about to start playing with different value inductive coils to compensate.. also don't forget mutual inductance where your live coil is being influenced by those extra 6 magnets sitting 1/2" away...

Another consideration is magnets... a big part of the HB sound is the bar magnet... a big part of the Strat sound is the 6 rod magnets.. whether you can use a combination or not I haven't considered, you may get good results..

I realise this info may be of no help to you being active related but... can I suggest you take two normal single coils and mount them side by side... by switching one in and out you should be able to see the effects of the dead coil on the live one in relation to mutual inductance without spending many hours building this pickup to find mutual inductance kills it.

I eventually came to the conclusion that by just changing the string aperature alone I could get the effects I needed to 'simulate' dual to single coil operation...hence the decision to use two stacked side by side coils..

Tone

9/3/2002 3:06 AM
Jason Lollar	What I did was split the strat coil in two so half of it was matched to the HB side by side then you can switch that out and have a full strat coil. It does work. Seems like all the good ideas have already been thought of.

9/3/2002 1:22 PM
Mark Hammer	Thanks First off, thanks to all for their thoughtful replies. This was useful information. I didn't expect such a design to be any sort of breakthrough, reasoning that if it was I'd probably be seeing glossy celebrity endorsements for it already. Tony's got it right when he alludes to string aperture. That's likely the part that stops this dead in it's tracks. If I've got it right, the requirement to use vertical polepieces to produce a stacked humbucker (as 2/3 of this assembly) means that even in side-by-side mode, the sensing area is not strictly between the tops of the two sets of polepieces (as it might be were one to use a bar magnet). You'd still get the hum-cancellation, mind you, in addition to a less noticeable volume drop than yo get when cancelling coils in a PAF-type pickup, but the tone would only be an approximation of a PAF-type HB rather than a clear replication of the specific means for getting that tone. Of course, I doubt that having 3 side-by-side coils (remember those old Hamer - no relation- guitars with the triple-coil bucker by the bridge?) with either a dual-rails or PAF-width aperture would necessarily would fix anything either. Assuming one had a bar magnet wide enough, how would you make the middle coil behave as if its' magnet structure didn't exist when aiming for the two outside coils? To my mind, the sensing area would be totally screwed up. Maybe the trick is to attack only one of the coil-cancelling demons at a time. Were one to overwind and tap one coil on a PAF-type, coil cancelling would be done on the normally-wound coil and simultaneously kick in the extra turns on the other coil. In principle, this would still not get you the hum-cancellation, but at least the volume drop would not be so noticeable. Of course, given that the sensing area is still between the two sets of polepieces, would it sound SC? It seems that elusive beast (the PU that can capture both personalities authentically) still eludes us. Of course that doesn't mean the tonal differences available by any of the configurations described wouldn't be musically useful. They just wouldn't nail specific types of tones.

9/3/2002 1:22 PM

Mark Hammer

Thanks

First off, thanks to all for their thoughtful replies. This was useful information. I didn't expect such a design to be any sort of breakthrough, reasoning that if it was I'd probably be seeing glossy celebrity endorsements for it already.

Tony's got it right when he alludes to string aperture. That's likely the part that stops this dead in it's tracks. If I've got it right, the requirement to use vertical polepieces to produce a stacked humbucker (as 2/3 of this assembly) means that even in side-by-side mode, the sensing area is not strictly between the tops of the two sets of polepieces (as it might be were one to use a bar magnet). You'd still get the hum-cancellation, mind you, in addition to a less noticeable volume drop than yo get when cancelling coils in a PAF-type pickup, but the tone would only be an approximation of a PAF-type HB rather than a clear replication of the specific means for getting that tone.

Of course, I doubt that having 3 side-by-side coils (remember those old Hamer - no relation- guitars with the triple-coil bucker by the bridge?) with either a dual-rails or PAF-width aperture would necessarily would fix anything either. Assuming one had a bar magnet wide enough, how would you make the middle coil behave as if its' magnet structure didn't exist when aiming for the two outside coils? To my mind, the sensing area would be totally screwed up.

Maybe the trick is to attack only one of the coil-cancelling demons at a time. Were one to overwind and tap one coil on a PAF-type, coil cancelling would be done on the normally-wound coil and simultaneously kick in the extra turns on the other coil. In principle, this would still not get you the hum-cancellation, but at least the volume drop would not be so noticeable. Of course, given that the sensing area is still between the two sets of polepieces, would it sound SC?

It seems that elusive beast (the PU that can capture both personalities authentically) still eludes us. Of course that doesn't mean the tonal differences available by any of the configurations described wouldn't be musically useful. They just wouldn't nail specific types of tones.

9/4/2002 3:28 PM
Tony@Mastertone	I think Marks right in regards to string aperture... even with the second HB coil electricly disconnected you still have the stack using the magnetic aperture of a HB... We need to devise a way of removing those rogue.. magnets to produce a true single coil aperture. Dynamite or how about 50,000 Volts..hehe. Tone

9/3/2002 6:57 AM
Andy	Re: Coil-swapping pickup - feasible? It will and does work. Because of my connection with Chris Kinman, I actually used some Kinmans in just this way and the results were.......average. Not stunning and not different enough to be worthwhile but satisfactory, they gave a particular customer the sound she wanted. However she has now changed to a more conventional arrangement. In summary a worthwhile experiment that does bear replication but not earth shattering and certainly not going to make our fortunes! Andy

9/3/2002 6:57 AM

Andy

Re: Coil-swapping pickup - feasible?

It will and does work.

Because of my connection with Chris Kinman, I actually used some Kinmans in just this way and the results were.......average.

Not stunning and not different enough to be worthwhile but satisfactory, they gave a particular customer the sound she wanted.

However she has now changed to a more conventional arrangement.

In summary a worthwhile experiment that does bear replication but not earth shattering and certainly not going to make our fortunes!

Andy

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