Pickup Magnetic Polarity and Phase

VVG-Logo3 In this article, Pete Biltoft at Vintage Vibe Guitars explains how the magnetic orientation and winding direction of single coil pickups affects their phase relationships and hum cancellation.

Thanks again to Pete for the permission to post this here!

Howdy!

In this newsletter I would like to cover how to “match” two single coil passive magnetic pickups. 

Consider all of the possibilities for magnetic polarity (north up or south up) and winding direction (clockwise or counter clockwise) for each of the two pickups as well as series or parallel connection of the two pickups and the possibility of the pickups being in phase or out of phase with each other and things can get a little complicated.

Let’s try to sort it out.

Most players just want three good and useful tones from an instrument with two pickups:

  1. Bridge position pickup only
  2. Bridge and middle position pickups both on (and most often connected in parallel)
  3. Neck position pickup only

In switch positions 1 and 3 all is good- no phasing issues are possible as there is only one signal from one pickup, but in switch position 2 the possibility exists that the two signals from the two pickups could be in phase or out of phase with each other.

Why would you care?

Let’s just consider switch position 2 in which both pickups are contributing to the signal going to the output jack of the instrument.

If these two signals are out of phase the result is often a thin, nasally tone that is not hum canceling. The tone of out of phase pickups has been used quite successfully by some players to create a very characteristic sound found often in Funk and Reggae. James Burton could coax a thin, out-of-phase sound out of his Tele—he called it the “little Chinese tone”. You can hear this sound on some of his famous recordings with Ricky Nelson, including Travelin’ Man. Jimmy Page also used the out of phase combination to very good effect. I bring this up to make the point clear: having the signals from two pickups out of phase with each other is not necessarily a bad thing. In the table below these out of phase combinations are highlighted in purple.

If the two signals from the two pickups are in phase and the pickups have the correct magnetic orientation and winding direction the result is a strong tone that is hum canceling. In this case the two pickups have opposite magnetic polarity and opposite winding direction with respect to each other. This is the configuration used in most modern instruments and is called reverse wound reverse polarity and is abbreviated RWRP. In the table below these in phase and hum canceling combinations are highlighted in green.

In some vintage instruments both pickups have the same magnetic polarity and winding direction; this configuration produces a reasonably strong tone but is not hum canceling. In the table below these in phase and non-hum canceling combinations are highlighted in yellow.

There are a total of eight possible configurations for magnetic polarity and winding direction for two single coil pickups; here they are:

Magnetic polarity and winding direction

Once a decision has been made regarding which of these eight pickup configurations is desired the remaining task is to make sure the magnetic polarity and winding direction of the two pickups is correct.

Note that for a desired configuration (RWRP for example) one must get both the magnetic orientation and winding direction for both pickups correct (options 1 or 5 in the table above). Purchasing a matched set of pickups configured as you want from a pickup manufacturer is often the easiest path to getting a desired pickup configuration. If you are faced with matching two pickups of unknown magnetic orientation and winding direction, changing the magnetic orientation or the effective winding direction on one of the pickups may be required. Note that changing the magnetic orientation will reverse the phase of a pickup; changing the effective winding direction will also change the phase of a pickup; changing both magnetic orientation and effective winding direction will change the phase twice and will return the pickup to its original phase orientation.

1.       Magnetic orientation.
I usually start with checking the magnetic polarity of the two pickups using a scout’s compass as shown in the photo below. Note that the compass in many cell phones use GPS data to determine direction and cannot be used to identify the magnetic polarity of a pickup.

If the top of a pickup attracts the red end of the compass needle the pickup I call this north up.

Magnetic orientation

If you find that the two pickups you want to install in an instrument have opposite magnetic polarity and you intend to have the pickups configured RWRP then you are half way there and can skip ahead to part 2: Winding direction.

If you would like to have RWRP configuration but observe both pickups have the same magnetic orientation you have a few choices:

A. If one of the pickups is designed to allow the magnetic orientation to be reversed then making this change will allow RWRP configuration. Many of the pickups offered by Vintage Vibe Guitars are specifically designed to allow the owner to remove and replace the magnets.

B. You can purchase one new pickup with the correct magnetic orientation to be paired with the pickup you intend to use. When making this purchase you will need to let the pickup maker know the magnetic orientation you want for the new pickup and also communicate the method used to determine the magnetic orientation of the pickup you want to pair with the new pickup.

C. You can purchase a new matched set of two pickups which are configured RWRP.

2.       Winding direction.
We will start here assuming that the magnetic polarity of the two pickups has been sorted out as described in section 1: Magnetic Polarity.

A. Using an analog multimeter to check phase orientation

Note: Detailed information on the proper use of multi-meters is available on: http://www.masonmonitoring.com/pdf/support/UsingMultimeter.pdf

To do this test, set the multimeter to the most sensitive DC voltage scale (1 volt full scale) and connect the probes of the multimeter to the output leads of the pickup. The leads should be connected as follows: red multimeter probe to the “Hot” lead of the pickup and the black multimeter probe to the “ground” lead of the pickup. With these connections made place a steel tipped tool on the top of the pickup then quickly pull the tool away from the pickup. You should observe a quick motion of the indicator needle of the multimeter either to the left or to the right. Most pickup manufacturers make pickups which will indicate a positive (right moving) deflection of the indicator needle in this test. If both of the pickups show deflection of the analog meter needle in the same direction the two pickups have the same phase orientation which is correct if you want the pickups to be in phase with each other. If you want to change the phase of the pickup go to section C. below.

B. Testing the pickups in the instrument

If an analog multimeter is unavailable I suggest installing the pickups into an instrument and listening carefully to the tone and output of the pickups in all three pickup selector switch positions. If you hear a low output, thin sounding tone in the middle (2) switch position it is likely that the two pickups are out of phase with each other. If this is the desired middle position tone, all is good, if not then the phase of the pickup must be reversed as described below in section C.

C. Changing phase orientation by reversing the effective winding direction

If you wish to change the phase of one pickup it will be necessary to reverse the assignment of the output leads on that pickup at the free end of the leads. First check that the output leads are independent of any grounded shielding on the pickup. In pickups with two leads and no shielding simply reverse the assignment of leads (use the black lead as the hot output and the white lead as ground). If the pickup has grounded shielding one would need to remove the connection between the ground lead (which usually has black insulation) and the copper shielding and install a new independent ground lead onto the shielding of the pickup. The new ground lead should be soldered to a known electrical ground in the controls cavity such as the casing of a grounded pot. If the pickup has an output cable with two independent conductors (often one with black insulation and one red or white insulation) inside a shield then one can simply reverse the assignment of the two internal conductors at the free end of the output cable. Maintain the connection of the external shielding to ground.

I hope you find this information useful.

Please visit the Vintage Vibe Guitars website (www.vintagevibeguitars.com) for more Tech Tips, wiring diagrams and of course a wide selection of pickups for guitar and bass.

Best wishes,

Pete Biltoft

Vintage Vibe Guitars
website: www.vintagevibeguitars.com
email: [email protected]