Oripure AlNiCo P-90 Neck and Bridge Analysis

[antigua]

These Oripure AlNiCo P-90 shaped pickups are are currently $40 a piece on Amazon, which aren't the cheapest pickups among Chinese made pickups, but are still a tiny fraction of what comparable boutique pickups cost, such as a Lollar AlNiCo P-90, at $110 per pickup.

As seen in the pics below, these bobbins are taller than a P-90, more along the lines of a Telecaster bridge pickup. The drawback of a tall, thin coil is that the output is lower when more of the electromagnetically reactive parts are farther from the guitar strings, and the lower permeability of AlNiCo means that less of the string's magnetic field is transmitted to the lower portion of the coil. So it would have been nice if this had thin/wide coils like a P-90, but on the plus side we can appreciate the idea that they're more like a Telecaster pickup.

They sell a "bridge" and a "neck" model, though the neck pickup has an inductance of 3.7 henries, while the bridge version has an inductance of the 6 henries, which is a wider spread than usual for a neck and bridge version of a typical pickup set. Some people might prefer two neck pickups instead, especially if you're looking for a Tele style pickups in a P-90 housing. In fact the bridge pickup has so much more wire on it that it's visibly much wider. While the neck pickup could be a Tele bridge pickup, the bridge's coil is so wide that it would probably not fit a Telecaster bridge bobbin.

Since the steel screws are replaced by less conductive AlNiCo, the Q factor is higher than with a regular P-90, so these might pair better with 250k pots, as Strats are Telecasters do with their AlNiCo poled pickups, and with 500k pots the treble at the resonance might stick out more, but rolling to the tone control back a little would have the same effect as 250k pots.

The AlNiCo pole pieces are said to be AlNiCo 5, and the flux density at the pole tops measured 900G, which is normal for AlNiCo 5 poles of that size and shape. Note that it's a "flat stagger".

They also put shielded copper tape, as well as regular insulation tape around the coil. The capacitance of the bridge started out at 180pF, but with the copper tape disconnected from ground, the capacitance dropped to 112pF, which is equivalent to about two feet of guitar cable. With a 470pF load, that pushed the resonant peak from 2.2kHz up to 2.5khz, that enough to make a slightly audible difference.

The copper take also causes eddy currents, though the effect is not dramatic. Without load, cutting the copper tape increases the amplitude at resonance by 3dB, but with load, the difference is about 1dB, which is barely audible. The good news is that since the coil has both regular tape and copper tape, it's very easy to peel the copper tape off without risking the coil, if you want to remove the tape and have a true Fender style AlNiCo single coil.

The pole pieces of both pickups are 50mm, which has to be taken into consideration since P-90 covers can come in a few different spacings.

The packaging is also very nice. It's probably only a matter of time until they start including a guitar pickup.

I'm planning to install them into a TV yellow Les Paul Special, but I'm not expecting it will sound like a Telecaster, because the pickups are still positioned as a Les Paul and not a Tele. I'm expecting it will sound mostly the same, but brighter and thinner, and that sharper sound you get when you have strong magnetic pull on the strings.


OriPure Solid Sound Soap Bar Pickups P90 Bridge
- DC Resistance: 9.370K ohms
- Q @1khz: 3.11
- Measured L: 6.164H
- Calculated C: 180pF (112pF with shielding disconnected)
- Gauss: 900G (AlNiCo 5)

OriPure Solid Sound Soap Bar Pickups P90 Neck
- DC Resistance: 7.013K ohms
- Q @1khz: 2.73
- Measured L: 3.7128H
- Calculated C: 217pF
- Gauss: 900G (AlNiCo 5)

OriPure Solid Sound Soap Bar Pickups P90
Bridge unloaded: dV: 9.4dB f: 5.57kHz (black)
Bridge loaded (200k & 470pF): dV: 3.5dB f: 2.23kHz (blue)
without shield, unloaded: dV:11.5dB f: 6.14kHz (black)
without shield, loaded: dV: 4.1dB f: 2.5kHz (blue)
Neck unloaded: dV: 9.6dB f: 5.48kHz (red)
Neck loaded (200k & 470pF): dV: 4.1dB f: 2.89kHz (green)




The bridge pickup, with and without the copper shield tape:

[stratotarts]

I notice that the additional clearance needed for tall bobbins, compared with the steel pole version, comes from the absence of permanent bar magnets and screw retainer bar. In spite of that, they also appear deeper, as the cover seems to not extend all the way to the bottom. Am I right about that?

[roadtonever]

I'm always intrigued with designs that combines ideas from Fender and Gibson camps. I wonder about the choice of a tall coil, it's looks like an appeal to Fenderisms, but at the same time the inductance is in the PAF range. Maybe sticking with either a lower inductance or a coil closer to the strings would give it a larger appeal.

[antigua]

Apr 25, 2021 8:05:46 GMT -5 stratotarts said:

I notice that the additional clearance needed for tall bobbins, compared with the steel pole version, comes from the absence of permanent bar magnets and screw retainer bar. In spite of that, they also appear deeper, as the cover seems to not extend all the way to the bottom. Am I right about that?

It's about flush with the cover. I think they made it tall because their AlNiCo 5 pole pieces are so tall. A shorter bobbin would have required more parts to account for poles that extend out the bottom. Or they could have used shorter AlNiCo poles which I'd guess cost more, and would be weaker than the taller ones they used, partly defeating the purpose. It would have been more expensive for the to have made the perfect AlNiCo poled P-90. 

I installed these pickups in a Les Paul Special, and discovered that the output is a low lower than the original P-90's unless I set the P-90's a lot closer to the strings. In the bridge position, the bottom of plastic cover almost eclipses the pickup cavity. I've never determined whether the strong magnetic field on an AlNiCo pole piece is able to make up for the loss of permeability of the alloy, but anecdotal evidence strongly suggests that it's not, and that you get more voltage with steel pole pieces, even if the flux density is more than halved. I think they would work good in a Telecaster, since Tele pickups are already closer to the strings and they were designed with AlNiCo poled pickups in the first place. 

[antigua]

Apr 25, 2021 9:01:21 GMT -5 roadtonever said:

I'm always intrigued with designs that combines ideas from Fender and Gibson camps. I wonder about the choice of a tall coil, it's looks like an appeal to Fenderisms, but at the same time the inductance is in the PAF range. Maybe sticking with either a lower inductance or a coil closer to the strings would give it a larger appeal.

They didn't seem as dark as I would have expected, but that could also be due to how they pickups are positioned in the guitar. What's lost in treble response might be mitigated by the trimbre. The pickup's coils axis are neither as close to the bridge nor the neck as they would be in a Tele or a Strat.  In any event, a comparison isn't apple to apples if the pickup positions are different. When the tone control is at 10, you'd never mistake them for PAFs, but with the tone rolled back, it would make for an interesting A/B touble blind. Maybe I'll give that a try when my friend comes by, I'll see if I can trick him with the AlNiCo P-90's.

[roadtonever]

Some people think a side by side humbucker is required for certain idealized PAF tone attributes. I've stuck to low output single coils for years now and I've found that with with additional caps and resistors I get close enough to the sound of a PAF that any small difference probably wouldn't matter in a mix. But I never did an actual blind test.