June 12, 2007
Last month, we discussed coil configurations, showing the four ways that a Fenderstyle single coil pickup can be wound:
- Clockwise with North at top
- Clockwise with South at top
- Counter-clockwise with North at top
- Counter-clockwise with South at top
Let’s dig a little further. In the early ‘50s, Fender’s guitars came with single coil pickups only. While the early Blackguard Teles gave the player the ability to combine the neck and bridge pickups together via a “blend” control, the Strat made no provision for combining coils.
Of course, all of these selections, including the Tele’s blended neck/bridge combination, picked up hum from the electricity in the building wiring. In the U.S. the alternating current in buildings alternates at 60 Hz (cycles per second). Thus, this hum has become known as 60-cycle hum, and is also harmonically rich – the image below shows the hum on a spectrum analyzer, and you can see the strong spike at the first harmonic (60 Hz), but you can also see the many spikes of other harmonics:
When Fender players started to learn of the cool tones that could be had by combining two pickups together, their tonal palette widened considerably, but the hum remained. Why? Because the two coils they were combining had the same wind direction and magnetic polarity. Therefore, whether combined in series or parallel, the hum stuck around. The solution was to combine two coils together with opposite wind direction, and opposite magnetic polarity.
Bill Lawrence has a patent drawing from the 1830s showing a device with two coils, where their opposing current direction resulted in hum-cancellation. But it wasn’t until the mid 1950s that this concept was applied to guitar pickups, and the result was the Gibson PAF (Patent Applied For) pickup, first produced in 1955.
Gibson used two coils for this pickup, and while both were wound in the same direction, they were wired together so as to have opposite current flow. They shared a single magnet, with one coil’s polepieces (steel slugs) in contact with the north pole of the magnet, and the other coil’s polepieces (adjustable screws) in contact with the south pole. You can see the magnet in the illustration below – it is magnetized such that the magnetic poles are at the long edges.
This resulted in a hum-canceling pickup, or “humbucker.” Combining two coils together in such a way that they had a) reversed current flow, and b) reversed magnetic polarity, producing a pickup that cancelled much of the hum. Taken individually, either coil would have produced the 60-cycle hum you might expect. But wired together in the right configuration, the hum was virtually eliminated.
It should be noted that this trick works regardless of whether the coils are connected together in series or parallel, so it’s an especially good trick. It also works with any two coils, by the way. Combine two coils together, where one is reverse-wound and reverse-polarity relative to the other, and you will have some degree of hum-canceling, due to phase cancellation. However, two coils with the same number of windings, and with equal magnet strength, will provide a greater amount of hum-canceling than two coils that are dissimilar.
And there is the definition of RWRP: a coil that is Reverse-Wound, and Reverse- Polarity, relative to the coil it’s being combined with. Of course, it’s a little bit of a misnomer, since the coil doesn’t actually have to be reverse-wound; it just needs to be connected in such a way that its current flow is opposite that of its partner. Perhaps RCF-RP would be a better term. But that’s just silly.
Understand that a RWRP pickup doesn’t sound any different than a non-RWRP one – they sound the same. In fact, wind direction and magnet orientation are completely irrelevant (except when combining two coils), which is why there is no universal standard.
In any case, this whole RWRP revelation provided some real benefits for Strat and Tele players, especially once those juicy “in-between” settings were discovered, allowing players to combine two coils on these guitars. Making a Tele’s bridge pickup RWRP means that it will hum-cancel when combined with the neck pickup. And making a Strat’s middle pickup RWRP means it will hum-cancel when combined with either the neck or the bridge pickup.
But how do you make these Fender pickups RWRP? Can you change their wind and magnet orientations? Come on back next month and we’ll jaw about it some more.
Founder, Acme Guitar Works acmeguitarworks.com firstname.lastname@example.org