Post by antigua on Feb 3, 2018 20:40:36 GMT -5
Mfg product link: store.gibson.com/p-94r-humbucker-sized-p-90-single-coil/
This is Gibson's "P-90 in a PAF footprint" hybrid pickup. It's as if a regular P-90 has been stretched downwards, to make the bobbin about twice as tall as it would be otherwise. The consensus on guitar forums has been that this pickup is not such a great P-90 stand-in, while some similar models from Seymour Duncan and Lollar get higher praise. So how close is this thing to a real P-90?? We shall see.
I received this P94R with an Epiphone Lee Malia Les Paul. I swapped this pickup out because I felt it was too dark at the time, and while I have come to realize that P-90's are "dark" in general, due to a higher inductance coil of about 6 henries. I was hoping for clear clean tones more associated with lower inductance PAF replicas, which tend to be closer to 4.5 henries on average, and are brighter as a result.
As can be seen in the pics below, the bobbin is much taller than that of a traditional P-90. This configuration puts more of the individual turns of wire further away from the guitar strings, and might slightly reduce overall output as a result. The moving magnetized guitar strings are the "action", and the closer a turn of wire is to that "action", the more voltage it produces. Due to the taller bobbin, the under-mounted magnets are also further away from the tops of the screws. I measured 350 gauss at the screw tops, which is just slightly less than the 400G I measured in the Tonerider Hot 90, which is a 'real' P-90 that also uses two AlNiCo 5 bars. The high permeability of the steel screws probably helps to mitigate the extra height of the coils, as compared to an overly tall bobbin with AlNiCo pole pieces, as less permeable AlNiCo does less to convey magnetic flux change up and down the core of the bobbin.
The P94R is also wider than a typical P-90, though the added width of the P94R doesn't factor into the electromagnetic properties of the pickup. As seen in pictures below, the extra width mostly involves a wider frame, and a couple small wood spacers to hold the magnets in place, as a full sized wood spacer does in a PAF pickup.
Here are the measured electrical values of P94R:
- DC Resistance: 7.76K ohms
- Measured L: 6.21H
- Calculated C: 279pF (289 - 10)
- Gauss: 350G
unloaded: dV: 4.9dB f: 3.76kHz (red)
loaded (200k & 470pF): dV: 1.7dB f: 1.99kHz (blue)
The loaded resonant peak of 2.0kHz and a resonant amplitude of only 1.7dB hits right in the general area of the other six P-90's I've tested, from Epiphone, and Tonerider 1, 2. On the high side I measured 2.3kHz, and on the low side 1.9kHz.
As far as I can see, there's no reason these should not sound indistinguishable from a generic P-90. If the P94 has AlNiCo 5 bars, it might sound more like a P-90 with AlNiCo 2 on account of the slightly reduced magnetic strength at the strings. That taller bobbin might also reduce the output slightly, compared to a real P-90. The P94R will sound a lot darker, or "muddy" than the PAF's it generally replaces. The average PAF clone neck I've measured is 2.9kHz , so the P94R, and P-90's in general, are substantially darker on average, with loaded resonant peaks closer to 2.0kHz. The only thing that gives hotter P-90's and cooler PAF's some parity is that the narrower magnetic window of the single coil P-90 retains higher harmonics that would be lost to the comb filtering effects of a side-by-side coil type pickup, or "humbucker". In other words, a single coil pickup will always be a bit brighter because it retains higher harmonics better. It's difficult to say how much one compensate for the other without some laborious practical testing.
Something that should be noted about the electrical values of the P94R, and other Gibson pickups, is that they include the 12" braided hookup wire, which impart about 70pF of added capacitance. This is partly why the overall capacitance is rather high at 279pF. I left the hookup cable in place since this is standard for the pickup. Another factor contributing to a high capacitance is the that the screws are grounded via the base plate, and so they capacitively couple with the windings of coil, where as a Fender style pickup's AlNiCo pole pieces do not. Fender also uses seprerate lead wires which capacitively couple to a much lower degree, and so altogether, you see a capacitance closer to 150pF for a similar type of Fender pickup.
Differences such as a nickel silver versus a brass base plate have shown to only have a tiny effect on Q factor in both PAF's and P-90's, so it's surely a non issue in the case of P94 style hybrids.