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FDP Forum / The 'Pup' Tent / Determining pup phase before installing



Apr 19th, 2003 09:39 PM   Edit   Profile  

This is something i learned years ago and it occured to me while reading another post that it's something a lot of people here may benefit from. I read a lot of posts where someone installed a new pup(s) only to find after re-assembling the guitar that one of the pups is out of phase, giving that thin sound when 2 pups that are out of phase are combined. So i figured that since no one seems to have mentioned this trick i'd post it and hopefully save some people from having to dis-assemble thier fender a second time to rectify the problem.

For those not familiar with pup phase problems, this is something that happens when one of the pups is out of phase with the other(s) and causes a thin weak output when the pups are used together as in the #2 and #4 positions on a strat. The fix is to switch the leads on one of the pups in a 2 pup guitar, or on the offending pup in a 3 pup guitar.

But to avoid this from happening in the first place, you need to know whether the pups are in phase when you install them so that you won't have to open the guitar up again and rectify it. On a start it's especially helpfull because unlike a les paul for example you can't just pop off a cover and reverse a wire. To do this you need a meter set to read ohms.

With the pup not installed yet,(or installed, but with selector set to that pup only and volume knob on 10) set the meter to 20k ohms (unless it's an autoranging meter of course) and put the red probe to either the ground or hot lead and the black to the remaining lead. Doesn't really matter which goes to which, but the important thing is that you REMEMBER WHICH WENT TO WHICH AFTER YOU TEST IT !

Once they are attached and the meter is correctly reading the pup's resistance, take a screwdriver or other magnetic rod shaped object and very slowly lower it towards the pup's polepieces starting from about 8" away. As the screwdriver gets closer to the magnetic field you will notice the resistance reading on the meter begin to change. It will either go up or down. REMEMBER WHICH WAY IT WENT AND WHICH PROBE WAS ATTACHED TO THE HOT AND WHICH TO GROUND !!

So lets say for example the red probe was attached to the hot wire and black to the ground wire, and the meter reading went UP. Test all other pups and they should be wired the same. In other words, if pup #1 was tested as above example where the red probe was attached to the hot wire and the meter went up when you did the test, then attach the red probe to the next pup's hot and black probe to it's ground and do the same test. If it goes up, use the lead that was attached to the red probe as the hot. If it went down, reverse it. (use the wire that was attached to the black probe as the hot wire.

To simplify (hopefully !)make sure that the pups are all installed so that the wire you use as the hot wire makes the meter go the same way in the test on all the pups. Get it? If not i'll try to clarify it if you need me too. It's one of those things that is very simple but hard to explain.

Contributing Member

Atlanta, GA USA

Apr 19th, 2003 10:22 PM   Edit   Profile  

Very cool tip there dazco. This really is required reading for anyone installing pups from different manufacturers into one guitar. Thanx.


Colorado USA

i need some sentimental hygiene
Apr 19th, 2003 10:23 PM   Edit   Profile  

Nice post Dazco, I usually get it right the third time. I am always suprised that the black wires aren't ground every time , or something to that effect, but what is more fun than pulling that pickguard out from under the strings again?



Apr 19th, 2003 10:54 PM   Edit   Profile  

"I am always suprised that the black wires aren't ground every time"

Actually, that brings up another point. Sometimes there is one pup that determines the way they will all be wired. For example, if there is one pup that must be wired a certian way like say a humbucker with a 2 conductor wire that can't be reversed because plate and screws would cause hum because they'd be hot. Then wire that pup as it's suppose to be and test it to see if the meter goes up or down with the probes attached for example with red to hot.
Then test the remaining pups with thier "hot" wire to red, and if the meter goes the same way wire it like that. Otherwise reverse them. A problem can occur when 2 pups that must be wired a certain way as in the above example aren't in phase when wiring them both as they need to be. In this case one must be modified by reversing the wires at the pup. In other words, the wire that goes to the plate ground must be switched with the hot.

In any case, the point is that if one pup has to have a perticular wire as the hot, test the others and if they are capable of being used with the wires either way, wire them so that they phase correctly with the one that needs to be wired a certain way.

By the way, another reason that one pup may need to be wired a certain way is if you have a humbucker that you sometimes used split, and there is one coil you favor to be the active one when split. Like with a bridge humbucker for example.......you may want the coil closest to the neck to be the active coil when split so that it's sampling the string further back so that it doesn't sound too tinny. Then again, you may want it the opposite if you DO want tinny.



Apr 20th, 2003 09:15 AM   Edit   Profile  

This is very good information to know. I'm always changing out pups and have run into this using fender and SD pups together. Appreciate it.



Apr 20th, 2003 10:13 AM   Edit   Profile  

what about the middle RW/RP pickup in a strat setup should it be different from the other two ????



Apr 20th, 2003 10:14 AM   Edit   Profile  




Apr 20th, 2003 10:16 AM   Edit   Profile  

I shoulda said that they are designed to be noise cancelling in the combined positions when in phase with non-RW/RP pups.


Boston, USA

Twang On!
Apr 20th, 2003 05:26 PM   Edit   Profile  

Cool technique!! Whats really maddening is what I have now: 3 Duncan SSL-1 strat pickups, each bought seperately online. Two of them repel each other when placed face to face, which should mean same polarity, use in neck and bridge. The 3rd attracts poles to the other two, and says "MIDDLE" on the stamp on back, so this should work fine in the middle for RWRP. I wire them all up, and viola!! The neck/middle is out of phase, and the neck/bridge is out of phase (using blender circuit). I thought having all Duncans, same model, would negate such problems. Now I gotta rip it apart and try reversing leads on something, I think I'll try the neck pup first, unless you guys have another solution.



Apr 20th, 2003 06:56 PM   Edit   Profile  

Just reverse the middle and it should be fine.


Boston, USA

Twang On!
Apr 21st, 2003 05:46 AM   Edit   Profile  

I reversed the neck, and it worked fine. Very strange why you'd have to do that with 3 Duncan SSL-1's, unless they changed the direction of the windings over the years, as these are all of different ages.



Apr 21st, 2003 08:11 AM   Edit   Profile  

oops.....just realized you said neck/bridge. I thought you said neck/mid and bridge/mid were out. Thats why i said to reverse the middle. Glad you didn't listen to me. :)


Los Angeles CA USA

Thanks, Leo......
Apr 22nd, 2003 01:42 AM   Edit   Profile  

What if one pickup is split to cancel hum (Precision), and the other isn't (Jazz)?

FDP Forum / The 'Pup' Tent / Determining pup phase before installing

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