Coil Tapping Opinions

OilCityPickups

thegummy said:

Funny thing about the tap/split thing is that people are so used to the wrong term being used they've reversed the meaning.

E.g. My Schecter bass has a coil tap and is labeled as such but in the Andertons video for it, Lee totally assumes it must be a split (and there for the pickups must be humbuckers when they're not) and even says how the silly people in the factory just put that tag on when it's wrong.

But it very much is the coil tap it said it is, Anderton just made an assumption that every time something says coil tap it's a misnamed coil split.

I get that all the time with my tapped single coils ... customers say 'noooo I don't want a humbucker' and I have to go through the painstaking process of explaining how a 'tap' works as opposed to a split. It's like the myth of DC resistance being a measure of output power. The problem is that once a term or concept has been misused or misunderstood for a long while it's almost impossible to stop its proliferation as hard fact. 

ICBM

OilCityPickups said:

I get that all the time with my tapped single coils ... customers say 'noooo I don't want a humbucker' and I have to go through the painstaking process of explaining how a 'tap' works as opposed to a split. It's like the myth of DC resistance being a measure of output power. The problem is that once a term or concept has been misused or misunderstood for a long while it's almost impossible to stop its proliferation as hard fact. 

It's a bit like the confusion between stacked humbuckers and mini humbuckers for Strats and Teles.

Or...

Tremolo/vibrato
Treble bleed/treble pass
'Out of phase' on a Strat

OilCityPickups

ICBM said:

OilCityPickups said:

I get that all the time with my tapped single coils ... customers say 'noooo I don't want a humbucker' and I have to go through the painstaking process of explaining how a 'tap' works as opposed to a split. It's like the myth of DC resistance being a measure of output power. The problem is that once a term or concept has been misused or misunderstood for a long while it's almost impossible to stop its proliferation as hard fact. 

It's a bit like the confusion between stacked humbuckers and mini humbuckers for Strats and Teles.

Or...

Tremolo/vibrato
Treble bleed/treble pass
'Out of phase' on a Strat

I love people's faces when they actually hear the disgusting noise a pair of Strat pickups make when out of phase ... priceless. 

and ... the rails/stacks/mini humbuckers/SC sized humbuckers thing is a nightmare of confusion.

CasperCaster

Alex_M said:

Thanks for the info, much appreciated. For those of you who have “factory” coil splitting, does anyone actually use it? 

Getting back to your original questions, I don't have any guitars with factory coil splitting, but it is a feature I add on my own instruments. As I predominantly play Fender style instruments I use an auto split on my HSS Strats, and usually voice the neck facing slug coil as I feel that in that instance (position 2; split bridge pickup in parallel with the mid pickup) I get the most useful result. I've yet to hear a split bridge pickup sound (when voiced on its own, without contribution from another pickup) that I truly love, despite having messed extensively with both resistor and capacitor splits, and hence why I have settled on the position 2 auto split. I'm fortunate that I have several Strats, so if I really need a true bridge single coil sound I use a different instrument.

Looking at things from a Les Paul perspective I'd be tempted to try either a resistor or capacitor split to get the option of a brighter sound, but be prepared that it will be quieter than the full humbucking output. If a brighter sound which retains at least some heft in the bass and low mids is what you desire then I'd personally try a capacitor split, but don't discount the resistor split idea (try a modern PRS if you want to know how resistor splits sound). 

Whilst I'm not personally a fan of parallel humbucking sounds, they might work for you. If your guitar has four conductor wiring and mini toggles for splitting, you could use three position on/on/on DPDT mini toggles to wire the pickups for series/parallel/split (or a three position 4PDT on/on/on to do both pickups together on a single switch). I'm sure the Dimarzio website (and probably others) have a wiring diagram for this. If nothing else you would be able to compare parallel versus split to see if you like either. 

You might also like to try a humbucking Yamaha Revstar with their DrySwitch - if you like what it does its easy to replicate and expand the idea. This is a really old (and simple) idea that Yamaha have revisited. It is just a simple low cut filter (cuts bass) which can help improve clarity, especially with a neck pickup or high gain. On humbucking guitars the instrument remains humbucking, but with less bass, such that the top end sounds more prominent (a neat psychoacoustic trick). A simple DPDT switch (either as a mini toggle, or as a push-push or push-pull pot) is all that's required. If you were to use a three position on/on/on mini toggle you could wire it for two different levels of bass cut. There is an interesting article about it below, and for once Dirk Wackers wiring diagrams actually look to be correct!

https://www.premierguitar.com/articles/29420-mod-garage-inside-yamahas-dry-switch

JayGee

Don’t some manufacturers actually use asymmetric taps (or a tap on one coil) on humbuckers to achieve a similar result to the PRS approach of slugging one coil a bit with a resistor?

I have vague recollection of a small UK manufacturer doing pickups where both coils had multiple taps, the idea being that by selecting different combinations you could approximate a wide range of common single coil or humbucker voicings and/or outputs...

CasperCaster

JayGee said:

Don’t some manufacturers actually use asymmetric taps (or a tap on one coil) on humbuckers to achieve a similar result to the PRS approach of slugging one coil a bit with a resistor?

I have vague recollection of a small UK manufacturer doing pickups where both coils had multiple taps, the idea being that by selecting different combinations you could approximate a wide range of common single coil or humbucker voicings and/or outputs...

Catswhisker Pickups S-bucker was reviewed in one of the guitar mags a couple of years back.

Gemini Pickups and Alegree also do humbuckers with taps (so they can be split and/or tapped).

Fender also do their Double Tap pickups, and I think it's implemented in some PRS's too (the models with two mini toggles and non-standard sized bridge pickup, 408??? ).

johnhe

I used to own an Epi Pro 339. Listened to harshly, to be honest, I didn’t like the sound of the split coils. But I still found it quite useful live.

over my years of playing I’ve had an almost totally consistently poor experience of any split humbuckers I’ve heard. I started having better experiences when I briefly owned a PRS McCarty, which I thought sounded pretty good when the pickup was tapped/split.

but the best experience was when I had a BK Mule put into the neck position of my 339. I had both coil split and a phase reverse switches installed. What I found, by accident, was that when the coil is split, if you reverse the phase, it dramatically changes the sound of the pickup. I assume it changes from the screw coil to the slug coil, but I’m honestly not sure.

in one position, it sounds like the normal, anemic, split humbucker tone. But when you also reserve the phase, the sound becomes much stronger and much, much more usable. I’m not saying it’s like playing a strat, but it’s the best coil split sound I’ve ever experienced. It sounded so good I had exactly the same arrangement instllled into my LP. It sounds even better in that guitar.

SlopeSoarer

The_Whisper_Thief said:

Lindy Fralins “Unbucker” is by a mile the best pup Ive heard when split. Its a great sounding humbucker to start with and then genuinely sounds like a strat pup when split. Guess it’s dependent on the guitar its in too

I have a AXL Torino which has a Lindy Fralin High Output Humbucker which is coil split and again sounds very Strat like. Just a very good pickup.

https://youtu.be/cd5SazQqKnA?t=134

HO Humbucker 2:14

Amigo

Going on a tangent here, sorry. In all humbucker coil splitting diagrams I saw the one unused coil was shorted, typically to ground. Now from what I know, voltage will be induced in that shorted coil in this case, causing a current through it, which in turn would induce a small voltage into the used coil through the magnetic circuit of the pickup, of opposing phase to the used coil's voltage, therefore further reducing the useful output of the used coil, emphasising the drop of volume. I would be curious to know how much is the effect of that induced voltage. Has anyone tried coil splitting without shorting? Does it make a big difference?

CasperCaster

Amigo said:

Going on a tangent here, sorry. In all humbucker coil splitting diagrams I saw the one unused coil was shorted, typically to ground. Now from what I know, voltage will be induced in that shorted coil in this case, causing a current through it, which in turn would induce a small voltage into the used coil through the magnetic circuit of the pickup, of opposing phase to the used coil's voltage, therefore further reducing the useful output of the used coil, emphasising the drop of volume. I would be curious to know how much is the effect of that induced voltage. Has anyone tried coil splitting without shorting? Does it make a big difference?

Sorry, but that assumption is not correct. Both ends of the shorted coil are tied to earth, so both ends are at the same potential (in this case earth), therefore no current can flow in the shorted coil. There is no induced voltage. 

As to whether it is possible to split a pickup without shorting, the answer is yes, at least with a four conductor + shield humbucker, but wiring would be unnecessarily complicated for no gain, since it won't make any difference for the reason I outlined above (assuming you compared like coils).

However, if you listen to the two coils of a PAF style humbucker independently it is clear that the two coils do sound different from each other (even if you rotate the pickup to retain the same relative position to the string). That is not surprising given a variety of factors - under normal circumstances the relative positions of the coils beneath the strings will be different (which probably accounts for the bulk of the difference), but there is also the different construction of the coils in a typical humbucker (e.g. screws and keeper bar versus slugs), so there will potentially be subtle differences in inductance between the coils, and in any case no two coils will be wound exactly the same (which affects inductance, resistance and capacitance).

It is possible to wire a split such that it voices the 'other' coil and is achieved without shorting the first coil (hypothetically, if a normal split to earth voiced the slug coil, then the 'other' coil would be the screw coil). This is done by joining the coil junction and hot together. So, the coil junction is effectively the output of the first coil, whilst the hot from the second coil is tied to the coil junction such that both ends of the second coil are at the same potential and therefore cannot contribute signal (analogous to a normal split where both ends of the shorted coil are tied to earth and at the same potential). Another advantage of this arrangement (as opposed to leaving the second coils hot floating) is that the second coil cannot contribute noise. 

urban_winter

Sorry, but that assumption is not correct. Both ends of the shorted coil are tied to earth, so both ends are at the same potential (in this case earth), therefore no current can flow in the shorted coil. There is no induced voltage. 

If that were true then no current could flow in any closed conducting loop. And that's not true. I guess the best demonstration of this is the superconduction demonstration where a conductive ring levitates over a magnet. If no current could be induced in the ring then it wouldn't levitate. 

ICBM

Coil-splitting without shorting the unused coil is often done, by using a switch to select either the full pickup or the coil junction to go to the hot output - but it has two problems, one is that the unused coil remains connected to the circuit and acts as an aerial for noise, and the other is that the signal has to pass through a switch contact, which makes switching noisier and potentially unreliable. Shorting the unused coil is by far the better way.

The current induced in the shorted coil is microscopic - I doubt it could have any effect on the other one. If you wanted to test it you could use an extra DPDT switch to take it fully out of the circuit and see if it makes any difference...

Amigo

urban_winter said:

Sorry, but that assumption is not correct. Both ends of the shorted coil are tied to earth, so both ends are at the same potential (in this case earth), therefore no current can flow in the shorted coil. There is no induced voltage. 

If that were true then no current could flow in any closed conducting loop. And that's not true. I guess the best demonstration of this is the superconduction demonstration where a conductive ring levitates over a magnet. If no current could be induced in the ring then it wouldn't levitate. 

Faraday's Law describes this phenomenon, and is the foundation of how the pickups work in the first place. Any coil/loop (and not even that, necessarily, even plain metal could do) of conductive material will produce a voltage if there is a changing magnetic field. If that loop is closed, even through its internal resistance, a current will flow through it, induced by the varying magnetic field. That current will be such that it generates a magnetic field opposing the initial magnetic field, according to Lenz's Law. The tendency is, therefore, to cancel any changes and bring back stability to the Force...

ICBM said:

Coil-splitting without shorting the unused coil is often done, by using a switch to select either the full pickup or the coil junction to go to the hot output - but it has two problems, one is that the unused coil remains connected to the circuit and acts as an aerial for noise, and the other is that the signal has to pass through a switch contact, which makes switching noisier and potentially unreliable. Shorting the unused coil is by far the better way.

The current induced in the shorted coil is microscopic - I doubt it could have any effect on the other one. If you wanted to test it you could use an extra DPDT switch to take it fully out of the circuit and see if it makes any difference...

I can see three ways in which this can be achieved, theoretically: 1) Short the unused coil; 2) Disconnect one end of the unused coil; and 3) Disconnect both ends of the unused coil.

Case 3) is the best, as it achieves a pure single coil, although the auditory impact is unknown... In case 2) the unused coil can act as an aerial, but at the frequencies involved that is very unlikely. Even if it picked up up some frequencies in the radio domain they would likely be cut off by various low-pass filters on route, beginning with the tone control (if fitted), so I don't think that would be that much of an issue. You do have a point with the switching being noisier potentially, though.

Case 1), which is the prevailing option, intrigues me. If the unused coil is shorted, the still-generated voltage—which was previously in series with the voltage produced by the other coil and driving potentially two 500kΩ resistors in parallel—is now seeing just the resistance of its own conductors, roughly half that of the whole humbucker, let's say 8kΩ / 2 = 4kΩ, nearly two orders of magnitude lower. It therefore means that the current through the shorted coil will be roughly two orders of magnitude higher. That would generate a magnetic field opposing the initial magnetic field, which will produce, through the mutual inductance of the two coils, whatever that may be, an induced voltage in the connected coil opposing the variations in the magnetic field produced by the strings. I hope this makes sense.

My curiosity was if anyone attempted to do a back-to-back comparison of a shorted-unused vs unshorted-unused, and if so, was there an interesting outcome? I am very unlikely to attempt such an experiment anytime soon, but if I ever do, I will report back for sure

axisus

Coil splitting is OK, it serves a purpose. For me though, Coil tapping just seems like a waste of time. I tried it a few times, different guitars and pickups and I just couldn't perceive the sound difference to a level that gave it any point. My last one I even put a meter on it to see if it measured different as I couldn't discern the change at all.

For me it is Eric Johnson battery swapping territory. 

CasperCaster

Well, I am intrigued - @Amigo you really do need to attempt such an experiment soon, and you definitely need to report back. With a four conductor humbucker, two toggle switches and a soldering iron, there is so little work involved that I do not understand why you are so reticent to try it? And whilst you are busy with some empirical testing may I also propose a Case 4 where you measure and/or audition the signal from the shorted unused coil.

Amigo

CasperCaster said:

Well, I am intrigued - @Amigo you really do need to attempt such an experiment soon, and you definitely need to report back. With a four conductor humbucker, two toggle switches and a soldering iron, there is so little work involved that I do not understand why you are so reticent to try it? And whilst you are busy with some empirical testing may I also propose a Case 4 where you measure and/or audition the signal from the shorted unused coil.

I have a guitar and 4-wire pickups, but they are both on sale here, so out of bounds for tinkering. If I sell them and I get a cheap guitar with some cheap 4-wire humbuckers, and if I have time, I will do this experiment. I was just checking to see if anyone attempted it.

In regards to case 4), the unused coil is important—in the case of coil tapping—by its impact on the main source of useful signal, namely the used coil, not necessarily as a signal source in itself. If the unused coil is shorted, measuring any voltage across it—for which tapping would be needed—is a can of worms, as Walter Lewin found out with his Super Demo and the amount of debate it stirred. Introducing any resistance in the loop to measure it would inevitably reduce the current through the shorted coil, altering the real effect on the used coil. Measuring current would be possible with a current clamp, but I do not have a current clamp for the low currents that I am expecting.

I did find, however, something which I may look into in more detail, as a theoretical exercise, both here
https://alexkenis.wordpress.com/2017/10/30/guitar-pickup-theory-8-humbucker-specific-coupled-inductance-peculiarities-and-more-magnet-myth-busting/
and here
https://www.slideshare.net/tininmartinez/fem-of-the-magnetic-field-of-guitar-pickupspdf

A consistent way of doing this exercise is the way I saw it done in an old Youtube video that I cannot find anymore, in which they used a custom-made coil placed on top of the humbucker to generate a deterministic signal and check the output. They used it to generate a frequency-sweeping signal to assess the frequency characteristic of the pickup, but in this case it would be to generate a predetermined signal and assess the output under different configurations. I may even attempt it at some point... although it might be of no more use than to confirm that I was wrong all along. Or maybe not?

ICBM

Amigo said:

In case 2) the unused coil can act as an aerial, but at the frequencies involved that is very unlikely. Even if it picked up up some frequencies in the radio domain they would likely be cut off by various low-pass filters on route, beginning with the tone control (if fitted), so I don't think that would be that much of an issue.

You’re making a lot of assumptions based on theory. In practice, the unused ‘floating’ coil *does* add noise, quite noticeably - in the guitar audio range, not RF.

You’ve got me interested in whether a shorted coil affects the sound of the other one though... it’s pretty easy to test, so when I have time and a suitable guitar to hand I’ll try it. I will definitely do it by disconnecting both ends of the coil.

Amigo

ICBM said:

Amigo said:

In case 2) the unused coil can act as an aerial, but at the frequencies involved that is very unlikely. Even if it picked up up some frequencies in the radio domain they would likely be cut off by various low-pass filters on route, beginning with the tone control (if fitted), so I don't think that would be that much of an issue.

You’re making a lot of assumptions based on theory. In practice, the unused ‘floating’ coil *does* add noise, quite noticeably - in the guitar audio range, not RF.

That is interesting, as the noise cannot then be in RF, if it is audible. Is it the humming noise, or higher up in the spectrum? It may be where the parasitic capacitances kick in, especially given that the one terminal still connected is usually grounded and shielded.

You’ve got me interested in whether a shorted coil affects the sound of the other one though... it’s pretty easy to test, so when I have time and a suitable guitar to hand I’ll try it. I will definitely do it by disconnecting both ends of the coil.

Based on a back-of-the-envelope calculation of what the chap in one of the links from my previous post stated, given a standard 5T inductance humbucker, one coil will have less than that, presumably, but let's say 2.5T. For a coupling factor of 0.15, the shorted coil would contribute about 15% against the signal. So, broadly speaking, half the signal of a humbucker and then another 15% of that. Whether such an amount would be audible, I would not know. However, it might affect different frequencies differently, probably more noticeable in the trebles than the bass.

I would be very interested in the outcome, should you ever attempt it. I would even put a bottle of single malt and haggis on the table in just over a week's time, were it not for the distance.

ICBM

Amigo said:

Based on a back-of-the-envelope calculation of what the chap in one of the links from my previous post stated, given a standard 5T inductance humbucker, one coil will have less than that, presumably, but let's say 2.5T. For a coupling factor of 0.15, the shorted coil would contribute about 15% against the signal. So, broadly speaking, half the signal of a humbucker and then another 15% of that. Whether such an amount would be audible, I would not know. However, it might affect different frequencies differently, probably more noticeable in the trebles than the bass.

I would be very interested in the outcome, should you ever attempt it. I would even put a bottle of single malt and haggis on the table in just over a week's time, were it not for the distance.

I will let you know, for sure - I'm interested now . I don't know how soon it will be but it's not a difficult thing to set up.

As you may have guessed I'm coming to this from the exact opposite direction from you - practical experience as a guitar tech, which I then try to understand the causes of. I particularly like doing direct-switching tests in real time on a guitar, since I think that's the most revealing of differences which aren't so clear if you have to stop and change something. Direct switching will show up really tiny changes, which you would never be able to say for sure made any difference if you didn't actually hear the sound change slightly - so much so that I'm confident that if you can't hear a change with direct switching (through a good transparent amp obviously), then it's probably correct to say there is none. But if you can hear one at all, then there is!

Amigo

ICBM said:

I would be very interested in the outcome, should you ever attempt it. I would even put a bottle of single malt and haggis on the table in just over a week's time, were it not for the distance.

I tried a basic simulation to compare the behaviour between shorting the unused coil and disconnecting it. Using basic values of 4kΩ resistance and 2.5H inductance for the coil, driving a 250kΩ load, and using a coupling factor of 0.15 there is an ever so slight decrease in the output when shorting the coil. Barely noticeable up to 100Hz where it gets to about 0.15dB lower, then to 100Hz the difference increases to about 1.3dB, and stays about the same thereon. So there is just over 1dB difference, but whether that is audible it is another matter. It does seem to affect the higher frequencies more than the lower frequencies, as I thought it might. Thought you might want to know