Electrical or magnetic polarity swap changing sound within a single humbucker?

[Ozram]

For a humbucker I always though that flipping the magnet or switching the "hot" (black) and "ground" (green) electrically would not change the sound of that pickup alone. Only when used together with another pickup - i.e. to get the Peter Green out-of-phase sound.

But: I have tried switching either electrically or flipping the magnet and both definitely changes the sound of my bridge position Custom Custom (for the time being with an A8 magnet). Compared to the normal configuration (south screw side, black = hot), this alternate position gives a fuller and sweeter kind of sound.

I actually prefer this "new" sound, but hate not knowing what causes it. Theoretically this does not make sense to me.
If it only was when I flipped the magnet it could have been other magnetic fields or rest/"leftover" magnetism in the slugs/screws causing a decrease in the magnetic field strength. However, same effect occurs with electrical polarity change without magnet flip. And in case anyone wonders, changing polarity both electrically and magnetically changes nothing (which makes sense).

Is it only an anomaly in my setup or is there anyone with similar experience?

Can anyone give me some clues to this effect?

 

[uOpt]

Re: Electrical or magnetic polarity swap changing sound within a single humbucker?

I wouldn't rule out that the field of the other pickup has a noticeable effect.

When measuring my magnets I can easily bridge the distance that neck and bridge pickup have and "see" the field.

If the field of the other pickup is noticeable, then the sound would change when you flip the magnet, because you reshape the resulting "averaged out" field.

If you want to dig into this I'd repeat the test with the other pickup removed.

 

[Ozram]

Re: Electrical or magnetic polarity swap changing sound within a single humbucker?

Yes, I suspect the neck pickup is in the equation as well. However, I also get the differences without any actual change of the magnets (just by electrical rewiring). Rewiring the neck pickup as well (to not have middle pickup position out-of-phase) does not affect the bridge pickup. But I will try removing the neck pickup - electrically or physically.

 

[Robert S.]

Re: Electrical or magnetic polarity swap changing sound within a single humbucker?

I would suspect that small changes in the pickups height after a flip/reinstall is having a bigger effect on tone than flipping the magnet.

Flipping the magnet and changing the hot lead does change the direction that current flows through the pickup and any changes can effect tone but to what extent you can actually hear a difference is up for debate. Pickup height changes on the other hand can make a huge and easily audible difference in tone.

 

[jeremy]

Re: Electrical or magnetic polarity swap changing sound within a single humbucker?

i have a phase switch on one of my main guitars bridge pup (a2 brobucker) blindfolded you wouldnt be able to tell any difference

 

[uOpt]

Re: Electrical or magnetic polarity swap changing sound within a single humbucker?

However, I also get the differences without any actual change of the magnets (just by electrical rewiring).

Is that a large difference? Did you maybe get the wrong wires?

Outside of your switch not 100% getting rid of the other pickup that aren't many explanations for this.

 

[Ozram]

Re: Electrical or magnetic polarity swap changing sound within a single humbucker?

I would suspect that small changes in the pickups height after a flip/reinstall is having a bigger effect on tone than flipping the magnet.

Flipping the magnet and changing the hot lead does change the direction that current flows through the pickup and any changes can effect tone but to what extent you can actually hear a difference is up for debate. Pickup height changes on the other hand can make a huge and easily audible difference in tone.

I agree with that. However, I get this effect also only by electrical rewiring without touching the pickup at all.

 

[Ozram]

Re: Electrical or magnetic polarity swap changing sound within a single humbucker?

i have a phase switch on one of my main guitars bridge pup (a2 brobucker) blindfolded you wouldnt be able to tell any difference

I agree. I also have a phase switch on the neck pickup and generally don't hear much of a difference (if at all). But the difference on the bridge pickup is definitively audible. Reversing the electrical wiring sounds fuller and rounder, but with some treble cutoff - so maybe there is some stray capacitive coupling that is altered.

 

[uOpt]

Re: Electrical or magnetic polarity swap changing sound within a single humbucker?

That's not possible, it's A/C anyway. I think it's more likely to be a wire problem of some kind.

 

[Ozram]

Re: Electrical or magnetic polarity swap changing sound within a single humbucker?

As I can not understand why it should have any effect reversing polarity, I also think it must be something related to the wiring. I have customized the electronics with quite a few options so there are definitively chance of a bad connection or poor soldering

My electronics (in a Washburn RS-10V) prior to polarity switching:
View attachment 10699


But I have not thought about this effect until I played with magnets in this Custom Custom. So I will also try another pickup again. (Swapping magnets did not change anything regarding this polarity effect.) Oh well still some investigation left...

Thanks for your input!

 

[Ozram]

Re: Electrical or magnetic polarity swap changing sound within a single humbucker?

A little update:

That's not possible, it's A/C anyway. I think it's more likely to be a wire problem of some kind.

Well, the signal is AC but there are various stray capacitances, e.g. between the shield wire and green wire, and between shield and black wire etc. But since the coils and wires are not identical (electrically and physically) these stray capacitances vary. Since you wire shield to either the green or black wire you will effectively short out some of these stray capacitances. Using a RLC meter I have measured this effect and have seen the capacitance (and thus resonant frequencies and frequency response) vary when switching phase electrically. However, I found that these pickup/coil capacitance differences are of a far lesser magnitude than just switching from a short to long guitar cable. And since I only hear a (very) subtle difference in sound going from a short to long cable (a slight loss of treble), the difference in sound of changing pickup polarity should be a lot smaller...
It is not, so I believe stray capacitances can not be blamed.

I have also tried bypassing all guitar electronics, just outputting the pickup straight to the guitar cable... effect still there. So I doubt my wiring is to blame.

I'm leaning towards this "phenomena" being caused by some freak electrical and magnetic interaction. I can now switch the bridge pickup polarity using a push/pull pot and hear the differences between the polarities. This is consistent in all pickups I have tried in this guitar now (both bridge and neck pickups - including the Invader which has symmetrical pole pieces in case that mattered...).

Well, until I hear this sound difference in another guitar, I just have to accept it. Maybe I just have a strange guitar (or effects proc., amp, room, house etc)... :1:

 

[uOpt]

Re: Electrical or magnetic polarity swap changing sound within a single humbucker?

I think that proofs that something else is screwed up. There's no way that the short pickup wire has capacitance that is relevant next to the pickup's capacitance of 15-40 nF - if it isn't broken.

What exactly were the measurements you got?

So you can if you connect your pickup wires directly to the guitar cable you get a different sound if you reverse the direction?

If I follow you correctly you say that you attribute that change to the fact that you now ground a different wire. I think if that is the case then you probably have a defective 4-conductor wire that has a partial shortcut between ground and one of the wires. I'd have to think more than I can on a Friday evening to say whether that would explain everything.

 

[Ozram]

Re: Electrical or magnetic polarity swap changing sound within a single humbucker?

I think that proofs that something else is screwed up. There's no way that the short pickup wire has capacitance that is relevant next to the pickup's capacitance of 15-40 nF - if it isn't broken.

What exactly were the measurements you got?

The stray capacitance within a pickup is not only between the different wires, but also from the coils to the shield and backplate etc.
And I would say a pickup's capacitance is far less than 15-40 nF (tone capacitors is typically in that range (or slightly larger)). Typically in the range of 80-150 pF (when not connected to anything). The capacitance difference between the two coils and shield/ground, i.e. connecting the shield wire to either the green or black wire, is typically less than 10-15 pF. However, I measured a short guitar cable I have to 160 pF and a long one to 580 pF. So you see that the difference in sound should be larger when switching cables than reversing the pickup polarity - if it has got anything to do with stray capacitances.

So you can if you connect your pickup wires directly to the guitar cable you get a different sound if you reverse the direction?

Yes (although it is a fairly small difference - not like something working or not, or a large loss of treble etc.)

If I follow you correctly you say that you attribute that change to the fact that you now ground a different wire. I think if that is the case then you probably have a defective 4-conductor wire that has a partial shortcut between ground and one of the wires. I'd have to think more than I can on a Friday evening to say whether that would explain everything.

No, I'm saying the opposite. I do NOT attribute the change to me grounding a different wire.

Note that I have tried several pickups (CC, Jazz, 59/Custom hybrid, Invader... all without faulty wires) and I get a sound difference in all. But have still only tried this with one guitar. So until someone reports this for another guitar, I choose to believe this is something with my guitar only. People should try for themselves.

 

[uOpt]

Re: Electrical or magnetic polarity swap changing sound within a single humbucker?

The stray capacitance within a pickup is not only between the different wires, but also from the coils to the shield and backplate etc.
And I would say a pickup's capacitance is far less than 15-40 nF (tone capacitors is typically in that range (or slightly larger)). Typically in the range of 80-150 pF (when not connected to anything).

Ozram, I measured all this stuff, pickups, individual coils in humbuckers, the cables, everything.

With the exception of full length guitar cables nothing comes in the same range as the pickups. The wires inside the guitar are way too short.

The capacitance difference between the two coils and shield/ground, i.e. connecting the shield wire to either the green or black wire, is typically less than 10-15 pF. However, I measured a short guitar cable I have to 160 pF and a long one to 580 pF. So you see that the difference in sound should be larger when switching cables than reversing the pickup polarity - if it has got anything to do with stray capacitances.

What does the guitar cable has to do with you reversing the wires in your 4-conductor pickup wire?

Your measurements for the guitar cable match mine but your claim has nothing to do with the guitar cable.

Yes (although it is a fairly small difference - not like something working or not, or a large loss of treble etc.)

So you need to measure the capacitance of your pickup with one and the other wire put to ground.

No, I'm saying the opposite. I do NOT attribute the change to me grounding a different wire.

Note that I have tried several pickups (CC, Jazz, 59/Custom hybrid, Invader... all without faulty wires) and I get a sound difference in all. But have still only tried this with one guitar. So until someone reports this for another guitar, I choose to believe this is something with my guitar only. People should try for themselves.

You say you get that for different pickups?

The trick of just reversing polarity directly into a guitar cable?

 

[Ozram]

Re: Electrical or magnetic polarity swap changing sound within a single humbucker?

What does the guitar cable has to do with you reversing the wires in your 4-conductor pickup wire?

Your measurements for the guitar cable match mine but your claim has nothing to do with the guitar cable.

I feel we are misunderstanding each other here.
Do we agree on a simplified electrical model of a pickup plus load as shown in attached figure? (E.g. see http://buildyourguitar.com/resources/lemme/)
Such a circuit shapes the frequency response of the pickup and hence how it transfers the sound of the guitar. Every change to the components, e.g. the pickup capacitance Cp or load capacitance Cload, changes the frequency response of the circuit (e.g. the resonant peak and 3dB cutoff frequency), possibly leading to audible changes.

I'm saying that by connecting the shield wire to either the green or black wire changes the value of Cp (i.e. changing the pickup polarity). E.g. for my CC its 84 pF when the shield is connected to the green wire and 90 pF when connected to the black wire - a change in Cp of only 6 pF.
The Cload is primarily made up of the total guitar circuit capacitance (depending on your wires, pots, switches and position of these) and the guitar cable capacitance. Changing from a short to long guitar cable of mine increases Cload by ca. 400 pF.

We can agree that a change in Cload of 400 pF should give more audible results than a change of 6 pF in Cp? However, I perceive the changes in sound to be larger when reversing pickup polarity vs. changing from short to long guitar cable. That's why I do NOT think changes in the stray capacitances (i.e. Cp) is to blame for the sound difference I hear when flipping polarity.
(Also since swapping magnet polarity changes the sound - not to my knowledge causing a change in Cp or any other component in the model.)

 

[Ozram]

Re: Electrical or magnetic polarity swap changing sound within a single humbucker?

You say you get that for different pickups?

The trick of just reversing polarity directly into a guitar cable?

Think I just connected the Jazz and '59/Hybrid directly to the guitar cable. The others using the out-of-phase push/pull (achieving the same, but with more load connected).

 

[uOpt]

Re: Electrical or magnetic polarity swap changing sound within a single humbucker?

Do we agree on a simplified electrical model of a pickup plus load as shown in attached figure? (E.g. see http://buildyourguitar.com/resources/lemme/)

Yes.

Such a circuit shapes the frequency response of the pickup and hence how it transfers the sound of the guitar. Every change to the components, e.g. the pickup capacitance Cp or load capacitance Cload, changes the frequency response of the circuit (e.g. the resonant peak and 3dB cutoff frequency), possibly leading to audible changes.

Yes, it's a second order low pass filter with resonance peak.

I'm saying that by connecting the shield wire to either the green or black wire changes the value of Cp (i.e. changing the pickup polarity). E.g. for my CC its 84 pF when the shield is connected to the green wire and 90 pF when connected to the black wire - a change in Cp of only 6 pF.

That's what I suspected, that somehow the capacitance changes when you switch the cables.

But this is why it's odd: The capacitance of your Custom should be around 20 nF, measured end to end over the coils in series.

Once you have a base 20 nF in the above filter a difference of 6 pF more or less isn't going to be audible.

Where are you measuring? From which wire to which?

The Cload is primarily made up of the total guitar circuit capacitance (depending on your wires, pots, switches and position of these) and the guitar cable capacitance. Changing from a short to long guitar cable of mine increases Cload by ca. 400 pF.

Yes, around 400 pF is what my higher quality long cables have.

We can agree that a change in Cload of 400 pF should give more audible results than a change of 6 pF in Cp? However, I perceive the changes in sound to be larger when reversing pickup polarity vs. changing from short to long guitar cable. That's why I do NOT think changes in the stray capacitances (i.e. Cp) is to blame for the sound difference I hear when flipping polarity.
(Also since swapping magnet polarity changes the sound - not to my knowledge causing a change in Cp or any other component in the model.)

I have a 12-position load capacitance turn switch in my pickup testing harness and yes, 0.4 nF give an audible difference.

I'd like to know from where to where you measured the 84 pF, exactly.

Keep in mind capacitance is complicated. Different capacitors of same value sound different, unfortunately. This greatly complicates these matters.

 

[Ozram]

Re: Electrical or magnetic polarity swap changing sound within a single humbucker?

But this is why it's odd: The capacitance of your Custom should be around 20 nF, measured end to end over the coils in series.

Once you have a base 20 nF in the above filter a difference of 6 pF more or less isn't going to be audible.

Where are you measuring? From which wire to which?

I measured the capacitance using a RCL meter capable of measuring impedance by sending a waveform (sinus I guess) with a specific frequency through the circuit to be tested and measuring the response. I measured between the green and black wire on the pickup - with shield connected to one of these and the red and white soldered together. Pickup was not connected to anything else. However, the frequency you use to measure the capacitance affects the reported measurement. I.e. below resonant frequency the RCL meter I used reports the impedance as a combination of resistance and inductance, and above the resonant frequency as a combination of resistance and capacitance. (Indeed I find the resonant frequency as the frequency when the impedance phase crosses zero.) To measure winding frequency I want to select as high a frequency as possible which gives me an impedance measurement consisting of primarily capacitance (phase angle close to 90 degrees). I measured at 100 kHz.

I have measured several pickups and they were all in the range of 80-150 pF (which corresponds to what others have measured e.g. http://buildyourguitar.com/resources/lemme/table.htm).

Yes, around 400 pF is what my higher quality long cables have.

I don't have a very good quality cable, so 400 pF was the INCREASE in capacitance going from a short to long cable.

I'd like to know from where to where you measured the 84 pF, exactly.

Between shield/green and black.

 

[uOpt]

Re: Electrical or magnetic polarity swap changing sound within a single humbucker?

My CC is 20 nF and that is what it is supposed to be. If the pickup was 84 pF then the 600 pF cable would just kill it.

I'm not sure what the impedance has to do with the capacitance and why you do to a different method above the resonance frequency, but in any case the reading is wrong.

 

[Ozram]

Re: Electrical or magnetic polarity swap changing sound within a single humbucker?

My CC is 20 nF and that is what it is supposed to be. If the pickup was 84 pF then the 600 pF cable would just kill it.

I'm not sure what the impedance has to do with the capacitance and why you do to a different method above the resonance frequency, but in any case the reading is wrong.

Supposed to be according to who? How did you measure 20 nF? Have you also measured the inductance?

The readings, according to "my method", are not wrong. DC resistance of my CC is on the lower side for a CC, 13.7kOhm, and I measure the inductance and capacitance to ca. 8.5 H and 85 pF, respectively. This gives me a theoretical resonant frequency of 5900 Hz - a res. freq. a bit higher than the CC listed on the SD Tone Comparison Chart (5200). Something I attribute partly to the lower DC res. and me just using a simple model/equation. It's fairly close to what I measure with the RCL meter though.

Adding your volume and tone pots as well as a cable changes the frequency response a great deal - but doesn't kill anything (flattens and with treble reduced though). I've tried to model it theoretically and show you the results on the figure attached (may not be entirely correct, but should be in the ball park). (Volume pot, tone pot, elec. and cable cap. included, but not any amp/effects input impedance.)

Effect of adding more capacitance: lowers the resonant freq., but increases the resonant peak.
Effect of adding lower value pots in parallel: lowers the resonant peak. (and resonant freq)

We might never agree on this topic though