Mismatched coil

[Mike Sulzer]

DC readings don't mean anything. Mever have, never will.

Now surely you are kidding. The resistance is an important factor in determining the Q, that is, how sharp the resonant low pass filter response is.

Remember: "Not everything that can be measured counts, and not everything that counts can be measured".

Well, the first part is right.

Trial-and-error is the only way to actually MAKE a p'up. All the ones that think otherwise are clearly in error, believe it or not.

No, but if you really think that the resistance has nothing to do with anything, then I can see why you believe this.

[John_H]

Isn't it true that a pickup wound with two equal coils will have a more focused resonant peak than a pickup with offset?

[LtKojak]

Now surely you are kidding. The resistance is an important factor in determining the Q, that is, how sharp the resonant low pass filter response is.




Well, the first part is right.



No, but if you really think that the resistance has nothing to do with anything, then I can see why you believe this.

Mike, we're not talking math here. The guy wants to actually build a p'up but he's got too much faulty internet hearsay hype indoctrination.

Btw, if I give you a sound, can you make a mathematical model or the specs of the p'up producing it?

[LtKojak]

Isn't it true that a pickup wound with two equal coils will have a more focused resonant peak than a pickup with offset?

That'll be the conclusive statement of my, although somewhat limited, hand-on experience.

But hey! What do *I* know, uh?

[Mike Sulzer]

Btw, if I give you a sound, can you make a mathematical model or the specs of the p'up producing it?

There are some factors you can determine either by listening or measurement if you have a good enough sound sample. For example, is it a standard humbucker or a single coil? The higher picking harmonics are audible on the single coil, and they are seen in the spectrum of the sound sample as well. There was a discussion of this a while back.

You can hear the location and height/width of the resonant peak, and you also can measure its spectrum from a sound sample. This works best if you compare the pu under test to a reference pu.

[David King]

Nice try Kojak!

[David Schwab]

1000 turns with #42AWG is quite a lot, where the same amount of #44AWG is almost nothing.

No, it's exactly the same; 1,000 turns. Stop thinking about the DC resistance. That's not what you are after when mismatching coils. The idea is to make one coil louder than the other, thus changing the frequency cancelation that happens.

[Lyrebird Steve]

I've acheived some good results working on a 52.5% / 47.5% ratio for PAF ... ie 5% differential.

Work out what your desired DCR is then build one coil to get 52.5% of this and a second to get the remaining 47.5% of it.

Using Salvarsan's coil estimator its pretty easy to figure out the corresponding number of turns per coil. (Esitmator also hosted here)

[copperheadroads]

I've acheived some good results working on a 52.5% / 47.5% ratio for PAF ... ie 5% differential.

Work out what your desired DCR is then build one coil to get 52.5% of this and a second to get the remaining 47.5% of it.

Using Salvarsan's coil estimator its pretty easy to figure out the corresponding number of turns per coil. (Esitmator also hosted here)

So based on 10000 turns 5250/4750 combo ,in neck pup territory .
IMO ,It's not a bad recipie for a bridge humbucker ,I like my neck humbuckers to have a a closer missmatch .as others posted .

[Joe Gwinn]

No, it's exactly the same; 1,000 turns. Stop thinking about the DC resistance. That's not what you are after when mismatching coils. The idea is to make one coil louder than the other, thus changing the frequency cancellation that happens.

If both coils are 1,000 turns, and they link the same changing flux, they will be equally loud.

So, the mismatch is a second-order effect of some kind. Agree that DC resistance has little to nothing to do with it.

[Mike Sulzer]

1000 turns is the difference between the two. They will not be linking the same changing flux because they sample different areas of the string. The resulting "filter" can reduce the sound of picking transients, rapidly damped very high harmonics. (There was a discussion of this showing the theory, measurements, and sound clips.) The differences achieved with a 1000 turn imbalance are not huge, but perhaps sufficient to matter to the highly motivated guitarist.

If both coils are 1,000 turns, and they link the same changing flux, they will be equally loud.

So, the mismatch is a second-order effect of some kind. Agree that DC resistance has little to nothing to do with it.

[Joe Gwinn]

1000 turns is the difference between the two. They will not be linking the same changing flux because they sample different areas of the string. The resulting "filter" can reduce the sound of picking transients, rapidly damped very high harmonics. (There was a discussion of this showing the theory, measurements, and sound clips.) The differences achieved with a 1000 turn imbalance are not huge, but perhaps sufficient to matter to the highly motivated guitarist.

This is the mismatch? Ahh. In a pair of 5,000 turn coils, this is a 20% difference, which is easily audible, as the self-resonant frequencies will no longer coincide.

[Mike Sulzer]

Yes, but the self resonant frequencies in coils of about 5000 turns are typically a bit above 10 KHz. More important is the resonance of the series combination of the inductors with the cable capacitance. That would be more like 4 KHz. You would have to model it to be sure though.

[bbsailor]

Yes, but the self resonant frequencies in coils of about 5000 turns are typically a bit above 10 KHz. More important is the resonance of the series combination of the inductors with the cable capacitance. That would be more like 4 KHz. You would have to model it to be sure though.

Mike, and all interested,

Here is an easy way to model it.
Inductance Capacitance Resonance Calculator
See the above web link for an online resonance calculator.

If you enter 400 pf as the total capacitance, including 100 pf coil self capacitance of two 5000 turn HB coils plus 300 pf for the coax capacitance then enter 4 Henries for 2 series connected coils of 2 Henries each, you get a resonance of 3978.874 Hz.

All passive high impedance pickups act like tuned resonant circuits with a resonance between 3Khz and 10Khz mostly controlled by the capacitance of the external load (coax cable capacitance). Buffering near or in the guitar reduces the impedance of the pickups and minimizes the effect of cable capacitance and keeps the resonant frequencies in the higher range.

Joseph Rogowski

[Mike Sulzer]

Thanks Joseph, but the circuit is more than a single resonance. You can identify at least three, the two self resonances, each involving a coil and its self capacitance, and a lower frequency resonance involving the cable capacitance and both inductors. A true analysis of this circuit must consider all the components at once, and could be done by direct analysis or by using a program such as Spice.

Mike, and all interested,

Here is an easy way to model it.
Inductance Capacitance Resonance Calculator
See the above web link for an online resonance calculator.

If you enter 400 pf as the total capacitance, including 100 pf coil self capacitance of two 5000 turn HB coils plus 300 pf for the coax capacitance then enter 4 Henries for 2 series connected coils of 2 Henries each, you get a resonance of 3978.874 Hz.

All passive high impedance pickups act like tuned resonant circuits with a resonance between 3Khz and 10Khz mostly controlled by the capacitance of the external load (coax cable capacitance). Buffering near or in the guitar reduces the impedance of the pickups and minimizes the effect of cable capacitance and keeps the resonant frequencies in the higher range.

Joseph Rogowski