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Thread: PJ bass wiring problem

  1. #1
    Supporting Member StarryNight's Avatar
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    PJ bass wiring problem

    I wound a P bass pickup and installed it in a Fender bass with J at the bridge. The reason I was asked to make one was the original P was way too hot compared to the J and the owner wanted a more balanced output. I whipped one up and I thought I wired it properly but when both pickups are full volume they cancel each other out drastically. I assume that one of the bobbins on the P is cancelling out the signal on the J. How does one get around the problem (if that's in fact the problem)?

    fyi I connected the two starts together on the P. Maybe I reversed the ground and the hot at the pot?

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    Ha Ha

    Where's that David Schwab guy when ya need him? Don't worry, he'll be by, he's the bass guy. He'll be able to help I'll bet.

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    Pickup Maker David Schwab's Avatar
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    Does it cancel out on all four strings? If it does, then just reverse the polarity of one of the pickups. They are out of phase with each other.

    If it's only canceling out on a pair of strings, then you need to reverse that one coil on the P pickup.

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    Supporting Member StarryNight's Avatar
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    The whole thing cancels out. He's coming over today with the bass. I'll report the results. Thanks DS.

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    Pickup Maker David Schwab's Avatar
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    Quote Originally Posted by StarryNight View Post
    The whole thing cancels out. He's coming over today with the bass. I'll report the results. Thanks DS.
    Just swap the two wires from one of the pickups. That will fix it right up!

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    The main problem with P-J set ups is that if you get the P and the J to cancel hum together then the P alone will be noisy *unless* you switch the polarity of one half of the P when it's soloed. You need a dpdt switch to do this, it can't be accomplished with a blend pot or two volumes that I can think of (It would be pretty cool if it could)
    The other obvious option is to wind a split J that matches the split P.

    Best of luck.

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    Pickup Maker David Schwab's Avatar
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    David, I'm assuming his P is set up like a regular humbucker and the J is a regular single coil, in which case you wont get the two to hum cancel.

    His issue is they are just out of phase.

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    Sure they will cancel if you want them to and the magnets are charged appropriately. Fender has been doing that for decades on their P+J models but they use a mini toggle pickup selector not a blend pot.

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    Senior Member mkat's Avatar
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    I think David S means that keeping the stock setup (no mod ie. switch) the way it is on that particular bass the two pickups together won't cancel the hum. The switch or humcancelling bridge pickup are options that could be presented to the customer.

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    As far as I know, that would not be the stock set up but the only PJ special I've ever looked at was a MIM job from about 1999. Who knows what other configurations Fender came up with in the meanwhile.
    I'd think that going to a non humcanceling config would seem a major step backwards.

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    Supporting Member StarryNight's Avatar
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    lesson learned

    well boys, the client returned the pickup before I could fix the problem. Being a relative beginner at bass pickups I have learned a valuable lesson. This was an example of what happens when the client doesn't get exactly what he asks for. Even though the fix would have taken less than 5 min. he wasn't satisfied with what he heard, got scared off and aborted the whole transaction. I can't blame the client, but I know had he been more tolerant, he would have walked away satisfied. A combination of his personality and my inexperience resulted in a lose/lose situation. To back up, I did the install (I like offering that for local players) and gave it back to him not realizing the P and J were out of phase. When he plugged in, he didn't like what he heard, removed the P I wound and returned it to me. I feel a little bruised but wiser for the experience. Next time I'll be more careful. Can't win 'em all.

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    Pickup Maker David Schwab's Avatar
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    Quote Originally Posted by David King View Post
    Sure they will cancel if you want them to and the magnets are charged appropriately. Fender has been doing that for decades on their P+J models but they use a mini toggle pickup selector not a blend pot.
    Every P/J I have seen has a regular P pickup, where each half has opposing magnetic polarity. Having them both on does not hum cancel the J pickup, since there is no hum in the P's signal.

    Also since the P is wound hotter than the J, they wouldn't hum cancel very well even if they were both single coils. Having a switch or a blend doesn't matter.

    A regular customer of mine has several Fender Aerodyne P/J basses, one with Barts and the others with the stock pickups. They all have regular hum canceling P pickups. One bass has a blend, and the other has a Gibson style toggle switch and two volumes that was wired up Gibson fashion. I changed them to work like a Jazz bass. It didn't, and doesn't hum cancel the single coil Jazz pickup.

    If the P had in phase coils and opposite magnets, half of the strings would be out of phase with the J. This would also be true if the P had the same magnet polarity on both halves, and were wired out of phase for hum cancelation (that's why you can't mix Delano split pickups with other pickups). There would be no sense in making the P non humbucking, since that's what the design is partly for.

    Getting back to the subject at hand... I always test replacement pickups for phase when installing them. You just never know exactly what you are going to get unless you wind both pickups.

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    I have a Fender MIM PJ set in my attic which I need to dig out now, I'm interested to see if the P is all the same polarity or N and S. Obviously the only way to get the combinations I'm talking about the P would need all the same polarity up to work together with the J. (Unless the J uses split magnets too.)

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    Pickup Maker David Schwab's Avatar
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    The J can't use split magnets unless it has two coils, like the DiMarzio Model J.

    There has been some threads at TalkBass where people were saying their P/J bass hummed when the J was in the circuit, and wondered what they could do about it. The answer was get a hum canceling J pickup.

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    The J can't use split magnets unless it has two coils, like the DiMarzio Model J.
    I don't see why not? What does it matter if two of the strings are out of phase with the other two on a single coil pickup (when it's soloed). It should only matter when two pickup's signals are out of phase on the same string or strings. No?
    see diagram below of 3 coils, dotted lines are strings:
    P J

    n...............s
    n...............s
    .....s..........n
    .....s..........n

    A true split coil J would be a better way of joining a P and J -I agree but it's not the only way to do it methinks.
    I guess an experiment is worth a few dozen words...

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  16. #16
    Pickup Maker David Schwab's Avatar
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    You are thinking strings.... it's only one coil. Half the coil will be out of phase with itself. Try it out and see.

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    Supporting Member StarryNight's Avatar
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    Quote Originally Posted by David Schwab View Post

    Also since the P is wound hotter than the J....
    I've got two questions:
    1. would this same delema occur in a guitar with a s/s/h configuration assuming there is a switch to activate both neck and bridge pickups? I never thought about it before but I guess one coil of the humbucker would be out of phase with the single coil.

    2. why is the P on a P/J bass wound hotter than the J? The whole reason this guy wanted a new pickup was the P was wound too hot, it sounded muddy and it over powered the J. Just like a guitar, the strings vibrate less closer to the bridge so wouldn't it make sense to wind the J hotter or at least even with the P?

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    Starry night,
    P pickups are probably hotter just because they have more turns (traditionally) than Js, i.e. 10000 turns or so for each P coil vs 8500 or so for a typical J. The magnet strength is also an issue. The J's gauss might have got knocked down (if they are alnico magnets) or the pickups might have been tossed together unthinkingly by Fender in a rush to get a new or cheaper product out the door.
    Most of the ceramic and steel pickups were much hotter than their equivalent A-5 loaded pickups.

    Typically the rear J pickup will need to be closer up under the strings to balance anyway so if the pickups were set the same distance then the bridge can't compete for the string excursion reasons you stated above.
    I'd just lower the P until I get a good balance if possible. That usually helps the sound too.

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  19. #19
    Pickup Maker David Schwab's Avatar
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    Quote Originally Posted by StarryNight View Post
    I've got two questions:
    1. would this same delema occur in a guitar with a s/s/h configuration assuming there is a switch to activate both neck and bridge pickups? I never thought about it before but I guess one coil of the humbucker would be out of phase with the single coil.
    What cancels noise, is noise. The humnbucker is presenting a composite signal of both coils in phase with each other in regards to the strings. It's not "seen" as two coils to another single coil, one in and one out of phase, just as one in phase pickup. There is no hum in the HB signal, so it wont hum cancel with another single coil. But you might hear less hum because of the signal to noise ratio with both pickups on.

    If you split the humbucker, and you use a coil with the opposite magnetic polarity and the right electrical phase, it will hum cancel to a degree.

    2. why is the P on a P/J bass wound hotter than the J? The whole reason this guy wanted a new pickup was the P was wound too hot, it sounded muddy and it over powered the J. Just like a guitar, the strings vibrate less closer to the bridge so wouldn't it make sense to wind the J hotter or at least even with the P?
    With the first P/J basses they just stuck on a stock P and J pickup. The J adds some highs to the tone, and of course you can solo them and have your usual P and J tones. Even the P/J basses I've seen with Barts, the P is much louder.

    I guess the problem is if you under wind the P, or over wind the J, you change the tone. But if you do each to a smaller extent, they should balance pretty well. Even on a stock Jazz bass, the bridge pickup is often weak compared to the neck.

    I had a P/J with DiMarzio pickups, and that was quite usable, but the J was still not as loud. One way around that is to put the P in parallel.

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    Supporting Member belwar's Avatar
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    Whats the standard winds on the P bass pickups .. I thought I read somewhere that it is like 10K per coil of 42? If they are in series thats a 20K passive pickup.. YOWZERS.

    I know nothing about these pickups but im learning about them now.

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    10 and 20K turns or ohms DCR? there's a big difference with such a small coil.

    I think of the first commercially successful PJ bass as the Guild Pilot bass from the mid 1980s. It came loaded with active EMGs for a time. Were there others before then?

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    Last edited by David King; 08-26-2009 at 06:20 PM.

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    Supporting Member belwar's Avatar
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    Someone told me 10000 turns per coil x 2, which would give a dc res of about 14.4-15k

    I dont know what I was thinking there about the 20k.. I guess I just had a brain fart.

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    Pickup Maker David Schwab's Avatar
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    Quote Originally Posted by belwar View Post
    Whats the standard winds on the P bass pickups .. I thought I read somewhere that it is like 10K per coil of 42? If they are in series thats a 20K passive pickup.. YOWZERS.

    I know nothing about these pickups but im learning about them now.
    It's 10,000 turns per coil, but not 10 Kilohms per coil. The whole pickup is about 11.6 k.

    Now on the other hand, the Gibson sidewinder (a.k.a. mudbucker) is about 20K!

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    Hi all...new guy here
    Had the same prob with my hobby bass...DiMarzio p (real hot) and an unknown j .had them wired with a blend pot that worked great for individual pups but the volume would cut drastically when both on .... I decided to go with the v v t wiring which lead to the same thing.... thanks for this post because it gave me reassurance that the j was wired out of phase. white wire and a red wire with a bare shielding for noise. turns out the red was hot not the white . problem solved. as for the balance issue I brought the j as high as possible and the p down to suit. great tone from this gem... ( an El Degas originally).
    the whole pickguard has shield tape which really helps with the "buzz" factor
    once again... thanks for the post

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    Last edited by TJBass64; 07-26-2012 at 03:34 AM.

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    Welcome TJB!
    When you got the phase straightened out was there still some hum with the VVs all the way up?

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    Anyone know how many turns per coil in a split coil Jazz? and what gauge is normally used? Nordstand use 42 and 43 it seems.

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    Kesh, I'm going to say that the turns count will be the same as in a single coil i.e. around 8500 or so. Where it gets tricky is when you have coils of uneven length on a 5 string bass.

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    I'm only planning on a 4 string luckily.

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    Pickup Maker David Schwab's Avatar
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    Quote Originally Posted by David King View Post
    Where it gets tricky is when you have coils of uneven length on a 5 string bass.
    You can wind them with the same number of turns, which hum cancels just fine, but then they sound a little different from each other.

    I haven't trid to find a way to fix that yet.

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    use a 6 string pickup with a dummy magnet?

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  31. #31
    Pickup Maker David Schwab's Avatar
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    Quote Originally Posted by Kesh View Post
    use a 6 string pickup with a dummy magnet?
    That would work. However, you can't fit two equal size coils into a Jazz bass pickup cover.

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    Quote Originally Posted by David King View Post
    Welcome TJB!
    When you got the phase straightened out was there still some hum with the VVs all the way up?
    Glad you asked....I had just re-wired the bass last night and only checked the sound through my pc.
    I just checked the bass, first with only the amp on ( markbass f500 connected to a 15" jbl in a kroth cab) and there was a slight hum with the grd lift on. tolerable. then plugged the bass in with vv's all up,not touching the strings or any other ground to the bass.
    results.... slight buzz only on the p with the t nob up... which dissappears when then string are touched. no noise on the j at all at full tone . buzz dissappears completely with all combos of v's with the tone full down. I am pretty impressed with the results being that the bass is passive. I'll work on getting some pics to post ....

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    Interesting results, I gather that the J pickup is some sort of humbucker.

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    as I said earlier.... the wires from the pu are shielded . a white, a red and the bare shield around both . they are attached to some sort of plate that shields the pu. wish I could i d the pu .... older model... maybe a fender noiseless ???
    Got it for 35 bucks about 20yrs back from a local guy that worked at a music store. It's all about the tone and I'm quite happy now that the "cut out" issue is gone.

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    I’m dealing with this right now with a build and it’s driving me crazy! With the P and J both at max in a VVT setup you get a dull, volume cut, sound. Moving back either volume even a tiny bit makes all the difference. Someone told me to swap the J’s leads to fix polarity, this made things worse if anything so I put them back to normal. Now someone is saying flip the magnet polarity on the J which I’m skeptical of since the lead swap didn’t help. Reading the above (provided I understood it correctly) matched my initial thoughts that a humbucking P and an SC J can never work perfectly with both maxed. Let me know if this sounds right to you? It seems logical since the two P coils are always going to be RWRP to each other... and adding ANY single oil to that mix is going to lead to at least half the strings being OOP... right?
    Chris

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