Middle toggle in parallel vs. pickup coils in parallel

[Inflames626]

Hi all,
So a common way I wire my passive guitars up these days is independent volume knobs for each humbucker and a tone knob. I also tend to put a push/pull phase switch on the neck pickup and a Shadow volume/killpot on the bridge.

I do independent volume knobs because I *think* my ears can hear a difference when I go to the middle toggle position and turn one pickup down. Usually I go to middle toggle and turn down the bridge pickup to get a slightly cleaner neck pickup tone. This seems to be a "less than series but not parallel coil" sound.

I know this is not the same as playing through a pickup with its coils in parallel. Here, the pickups themselves are in parallel but the coils are in series.

So, if you go to the middle toggle position, does this thin out the tone of the pickups somewhat through the toggle switch, or am I imagining it?

It doesn't seem to same as playing both pickups at the same time in their respective toggle positions or through each other in a megabucker wiring scheme. It's like playing both pickups through the middle toggle sums them both, but also reduces their output a bit so the middle position doesn't become twice as loud as the neck or bridge pickup playing alone.

For my cleanest sound, usually with a neck pickup, I will go to the middle toggle position, turn down the bridge pickup to isolate the neck, put the neck pickup in parallel with a Triple Shot, and use an out-of-phase tone all at the same time.

If using the middle toggle position does thin the pickups tone a bit, this gives me another tone to use that is less than series but not fully parallel, especially when I isolate one pickup by turning the other down.

I'm aware that independent volume knobs will change the treble response as the knob is turned down and that Strat guys have all these treble mod modifications for it.

Hope this makes sense.

Thanks.

 

[Supernautilus]

I'm not sure I completely understand your question. But I do know that the middle position on most 2 pickup guitars will put them in parallel, which cuts the output significantly. This is generally what gives you that "thin" sound. Unless you run both pickups in series, which is possible with certain wiring configurations, it's always going to sound thin. Hope that helps.

 

[Inflames626]

I'm not sure I completely understand your question. But I do know that the middle position on most 2 pickup guitars will put them in parallel, which cuts the output significantly. This is generally what gives you that "thin" sound. Unless you run both pickups in series, which is possible with certain wiring configurations, it's always going to sound thin. Hope that helps.

Supernautilus, I'm basically asking if a neck pickup in the middle toggle position with the bridge pickup turned all the way down makes a different sound than the neck pickup in the regular neck toggle position.

Otherwise there isn't much of a reason to bother with independent volume knobs.

I think I hear a difference. Like I said, middle toggle with neck pickup isolated sounds like a little less than neck pickup alone, but not as thin as neck pickup with coils in parallel.

Hope that makes it clearer.

 

[Supernautilus]

Supernautilus, I'm basically asking if a neck pickup in the middle toggle position with the bridge pickup turned all the way down makes a different sound than the neck pickup in the regular neck toggle position.

Otherwise there isn't much of a reason to bother with independent volume knobs.

I think I hear a difference. Like I said, middle toggle with neck pickup isolated sounds like a little less than neck pickup alone, but not as thin as neck pickup with coils in parallel.

Hope that makes it clearer.

Ok I think I see what you mean. Well, even with the volume turned all the way down, I think there is still a tiny amount of a connection there. Whereas in the neck position the bridge pickup is cut completely out of the circuit by the selector switch. So electrically there is a small difference. Whether that makes any sonic difference is something I'm not sure about. I would trust your ears on that one and listen to what they tell you.

 

[marcello252]

I think tgis way you are modifying the Q of the frequency resonant peak adding a pickup and its pot in parallel, actually a LRC load in parallel (although C might be negligible) , I think freefrog is the maximum expert in this field

 

[Inflames626]

I think tgis way you are modifying the Q of the frequency resonant peak adding a pickup and its pot in parallel, actually a LRC load in parallel (although C might be negligible) , I think freefrog is the maximum expert in this field

freefrog knows everything and has the data to prove it.

 

[freefrog]

Only God if he exists knows everything. The humble freefrog just tries to post only on things that he thinks to understand at least approximatively. ;-)

With independent volumes and switch in mid position + one of the pickup muted, this "disabled" pickup leaves in the circuit the parasitic capacitance of its wiring. If this stray capacitance is high enough, it slightly shifts down the resonant peak of the other pickup, in frequency and amplitude.

HTH.

 

[beaubrummels]

So the answer is "slightly"

 

[Artie]

I'm not sure I completely understand your question. But I do know that the middle position on most 2 pickup guitars will put them in parallel, which cuts the output significantly.

I'm not sure where this perception comes from. Both pickups "on" does not cut output at all. If anything, it slightly boosts it. Twice the current capability, to drive the next stage. (Amp and/or pedal input.)

I hope you aren't relating ohm meter measurement to voltage output.

 

[freefrog]

I'm not sure where this perception comes from. Both pickups "on" does not cut output at all. If anything, it slightly boosts it. Twice the current capability, to drive the next stage. (Amp and/or pedal input.)

I hope you aren't relating ohm meter measurement to voltage output.

I think this perception comes from the fact that two pickups in parallel have half the inductance of a single pickup (or 1/4 of both inductive values added to each other). The resonant frequency shifts up accordingly, making the coils more sensitive to higher frequencies and less sensitive to lower ones.

Electrically, it's not different of what happens when a single humbucker is wired in single coil mode or in parallel: a Hot Rails in parallel has an inductance of 3H (vs 6H split and 12H in series) and its output drops while its resonant frequency shifts up, making it brighter.

I think the reason why the output doesn't drop when a neck pickup is in parallel with a bridge one is how they complete each other: as if the neck transducer was a boomer and the bridge PU, a tweeter, so to speak.

I put below a screenshot showing the induced resonant peaks of two Duncan HB's in a guitar with 500k pots: a SH1B, a PGN and both in parallel. One can see how the parallel position lowers the signal of 3dB until the resonant peak comparatively to the bridge position (electrically only, exactly like the electrically weaker PGN is not weaker sounding than the SH1B, because the vibrations of strings have a greater amplitude above the neck slot and send a stronger signal to the neck transducer).

FWIW: another attempt to share.

 

[Inflames626]

I think this perception comes from the fact that two pickups in parallel have half the inductance of a single pickup (or 1/4 of both inductive values added to each other). The resonant frequency shifts up accordingly, making the coils more sensitive to higher frequencies and less sensitive to lower ones.

Electrically, it's not different of what happens when a single humbucker is wired in single coil mode or in parallel: a Hot Rails in parallel has an inductance of 3H (vs 6H split and 12H in series) and its output drops while its resonant frequency shifts up, making it brighter.

I think the reason why the output doesn't drop when a neck pickup is in parallel with a bridge one is how they complete each other: as if the neck transducer was a boomer and the bridge PU, a tweeter, so to speak.

I put below a screenshot showing the induced resonant peaks of two Duncan HB's in a guitar with 500k pots: a SH1B, a PGN and both in parallel. One can see how the parallel position lowers the signal of 3dB until the resonant peak comparatively to the bridge position (electrically only, exactly like the electrically weaker PGN is not weaker sounding than the SH1B, because the vibrations of strings have a greater amplitude above the neck slot and send a stronger signal to the neck transducer).

FWIW: another attempt to share.

Thanks freefrog. Knowing there is some difference, even if just a little, justifies my doing independent volume knobs because it gives me even more tonal flexibility.

I was drawn to this because I thought parallel coils made one kind of sound. Parallel pickups at vastly different string locations (relative to a single pickup's coils) would make another sound.

And you can always blend them like a Jazz bass even though I tend not to.

 

[Artie]

I think this perception comes from the fact that two pickups in parallel have half the inductance of a single pickup . . .

I love those graphs. How do you make those?

 

[freefrog]

I love those graphs. How do you make those?

With an ultra-low impedance air coil to excite the pickups, according to the recipe shared a few decades ago by Helmuth Lemme. And a frequency analyzer.

Different coils and analyzers give different data. For the most "serious" tests, we have some nice lab hardware devices at disposal here.

A few other folks do similar things elsewhere on the Net, with various methodologies. On the guitarnutz website, they like to use an "integrator" converting the voltage in current and giving a flat response in the bassrange while the resonant peak remains... This method has the advantage to make eddy currents obvious but the downside to "falsifiate" the results IMHO. There's other ways to measure Foucault currents (like the difference in measured inductance according to the test frequency used).
Another variation is in how to lay the exciter on the coils. At guitarnutz, they systematically put the air-coil perpendicular to the coils and between them when the pickup is an humbucker. That's what I've done myself in the graphs above but I also like to test each coil with the exciter parallel to it, because it makes obvious some quirks due to capacitive coupling...

Anyway: such tests are doable with a very basic gear if needed. A few turns of wire around a frame to make a low impedance air coil, a frequency analyzer freeware and a calibrated soundcard with a 1M input do the job.


Merry Xmas, ArtieToo and everybody!

 

[Artie]

Merry Xmas, ArtieToo and everybody!

Back atcha, bro.

So, you believe that Eddy currents are a significant factor in pickup sound? I never have, because they are so microscopic in amplitude relevant to the primary signal. But I'm starting to come around to accepting them since I see more and more people identify with them / it.

 

[freefrog]

So, you believe that Eddy currents are a significant factor in pickup sound? I never have, because they are so microscopic in amplitude relevant to the primary signal. But I'm starting to come around to accepting them since I see more and more people identify with them / it.

I believe that if Bill Lawrence did design his pickups to avoid Foucault currents, it's not without reason.

Related link: http://www.billlawrence.com/Pages/Pickupology/eddy_currents.htm

I also like his analogy stating that eddy currents are like salt in soup:

http://www.billlawrence.com/Pages/Pickupology/External Interference.htm

Anyway: if we consider that Foucault currents explain most of the tonal changes coming from pickup covers, from baseplates of different materials and even partly from various magnetic alloys, they are not necessarily so negligible.

The sound of a Burns Tri-Sonic single coil, for instance, appears to me as shaped mostly by eddy currents. Pulling off their metal baseplate kills their specific character (hence the fact that I don't like much the Brian May DiMarzio single coils encased in plastic).

There's an interesting pic about Foucault currents in the old Helmuth Lemme page: the fig. 5 - while the fig. 11 shows how to excite electrically a pickup with an air coil): http://buildyourguitar.com/resources/lemme/


FWIW. Merry Xmas again!

 

[Artie]

FWIW. Merry Xmas again!

Thanks. Nice links.