What does RWRP mean?

What does RWRP mean? - Reverse Wound, Reverse Polarity.

Why do pickups use this? - To cancel hum, reducing unwanted noise.

Does it change the tone at all? - No, it doesn’t.

There ends the simple explanation, for a more detailed explanation, read on below.

If you’d like your set all wound in the same direction, we can do that, just like they did back in the 50s, no problem!


How does RWRP actually work?

First – Reverse Wound, the RW part of RWRP

This hum cancelling technique has been around since the beginning of Electricity and shows up in Patents going back to the 1920s, possibly earlier. The term for hum cancelling by use of two coils of opposing wind direction is called a “Common mode choke” and they’ve been used widely inside amplifiers and other circuits to cancel out spurious noise.

Coils are antennas and apart from picking up your guitar strings, they also pick up Electro-Magnetic Interference (EMI) or noise. By adding a second, reverse wound coil and connecting it to the first, any noise that hits them is cancelled out.

If you have two coils in a circuit, for example, Telecaster Bridge and Neck pickups and your pickup selector switch is in the middle position, both coils are in use. With both coils wound in the same direction, the noise is summed in phase and becomes additive = louder noise in middle position. With two coils wound in opposing directions, the noise is summed out of phase and becomes subtractive = quieter in the middle position.

All you need to cancel hum are two coils wound in opposing directions. Magnets don’t cancel any hum.

Second – Reverse Polarity, the RP part of RWRP.

This is about magnetic polarity.

Say we have a Tele bridge pickup coil wound clockwise and our Tele neck pickup coil wound counterclockwise and they’re cancelling hum as intended. Next we introduce the magnet. If both pickups had magnets facing South up (towards strings) and the coils are wound in opposing directions then the resulting signal in the middle position would be out of phase - nasal and very thin sounding. The opposing coil winds put your pickups 180 degrees out of phase, so we flip the magnet in the neck pickup to have the North end facing the strings. This will add another 180 degrees of phase shift for a total 360 degrees, leaving the coils to cancel noise and your guitar signal big and beautiful! Both guitar pickups are working together cancelling hum, and sounding how they should.

Of course, if you have any questions, hit us up and we can chat about it.

Cheers, Ben Bailey.

 

Posted 18 September 2021

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