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now this is a strange problem, Please help!

Discussion in 'Luthier's Corner' started by tuBass, Jan 13, 2003.


  1. tuBass

    tuBass

    Dec 14, 2002
    Mesquite, Texas
    OK, I have a buddy that seems very knowledgeable about working on basses and customizing electronics. He built me a very nice 2x8 cab, has done tons of custom electronics on his own basses and adding onboard pre-amps ect....

    I wanted to add a bridge pickup to my son's bronco bass, so I did the routing job and gave it to him to do the wiring. For simplicity, I had him leave the tone knob as is, and wiring both pickups into the volume. In other words, there is no blend knob or switch. The pickup we put in was a noiseless fender Jazz that he pulled out of a brand new Jazz deluxe that he bought and promptly customized.

    Here is the problem. the G and D strings sound great, but the A and D strings sound weak and thin, almost dead, but there is alittle output, like a cheap old AM radio Tried a different set of strings, same problem. I tapped the pole peices with the end of a screwdriver, and the tapping output seems the same on every polepiece.
    My first thought was that something was wrong with half of the fender pickup, but even if that low string coil was out, I still should be getting sound out of the neck pickup, which was loud as blazes until I added the bridge pickup and the problem started.

    Any help would be greatly appreciated.

    Mark
     
  2. Trevorus

    Trevorus

    Oct 18, 2002
    Urbana, IL
    try reversing the polarity piezo pickup. you might also try a preamp that is made not to be changed, and a blend control between the two pickups. Ask you wiring guru to check it out too.
     
  3. FBB Custom

    FBB Custom TalkBass Pro Commercial User

    Jan 26, 2002
    Maryland
    Owner: FBB Bass Works
    Just a guess: the hum-canceling jazz pickup is a split coil pickup and the bobbin under the E and A strings is out of phase with the bobbin of the P pickup under the E and A string.

    You would be able to verify this if you had a blend knob and with the pickups run individually the string balance was good.
     
  4. tuBass

    tuBass

    Dec 14, 2002
    Mesquite, Texas
    I think I understand the out of phase part, but the neck position pickup is a dimarzio humbucker, with two coils running the width of all 4 strings.
    Does this change you diagnosis at all?
    I am am really scratching my head over this one, as is my buddy. If worse comes to worse I could add a blend knob, or individually controlled volume knobs. I was hoping not to have to so that because there is not really room on this small bass to add another knob without making it look very crowded.

    thanks again for you help, if there are other tips or ideas I would love to hear them
    Mark
     
  5. tuBass

    tuBass

    Dec 14, 2002
    Mesquite, Texas
    Here is the latest.
    I took FBB's advice and checked the phasing. The pickups were wired as properly as I could hav imagined, the fender wire was yellow, and it was run the to correct post on the volume pot, and the dimarzio hot, which is red, was run to the same post. Blacks were grounded properly, so i didn't switch anything, but while I was looking at all of the connections, the hot dimairzio wire came loose from the pot. Instead of breaking out my soldering iron at midnight, I decided to put it all back together and see what happened.
    The J pickup now work perfectly now that I have disconnected the dimarzio humbucker.
    Is it possible these pickups are incompatable with each other, or do I really need a blend knob or separate volume knobs? I would really like a two pickup setup to give the right balance of bite and body.
    Thanks again,
    Mark
     
  6. Brooks

    Brooks

    Apr 4, 2000
    Middle East
    Why not install a stacked Volume/Blend pot or a stacked Volume/Volume pot? Either way you will have more cotrol.
     
  7. dprives

    dprives

    Apr 22, 2002
    SF Bay Area
    The problem is probably that your new pickup has two windings that are out of phase to cancel hum; one winding for e &a and one for d&g. One of those windings, the e&a winding, is out of phase with the old humbucker. Therefore the signal from the new pickup and the old pickup cancel each other out and you all you get is a small, weak sounding signal. The two pickups are probably not compatible. I don't know for sure that your pickups are constructed like this but that's what it sounds like.
     
  8. tuBass

    tuBass

    Dec 14, 2002
    Mesquite, Texas
    I did consider that, but I didn't go in that direction for two reasons. First, this bass is for a six year old, and I was trying to keep the controls as simple as possible. Second, the my friend doing the wiring was doing for next to nothing, so I was trying to keep the job and labor as simple as possible.


    That's exactly what the new pickup is like, and the old pickup hastwo windings that cover all four strings. I hope this doesn't automatically rule out out using these two pickups with each other. I could replace the top humbucker with another Jazz or a P-bass style pickup, but I really don't want to do the work. I have put much more time and energy into this bass than it is worth, and I really hope I can can find a way to have the to pickups work together. Would adding a blend knob help the phasing problem? I wuold probably have a blend that was more bridge than neck, but I would like a little of that neck sound.

    Thanks,
    Mark
     
  9. i think the 6 year old would be just as happy without the bridge pickup....:)

    man to think if i started at six instead of last year...:cool:
     
  10. tuBass

    tuBass

    Dec 14, 2002
    Mesquite, Texas
    probably, but I'm the one who has to listen to him. I don't like the sound of a neck-only setup, so the modifications are more for me than him.
     
  11. dprives

    dprives

    Apr 22, 2002
    SF Bay Area
    I could be wrong, but it sounds like you’re hosed. A blend knob wouldn’t help any. You still have the fundamental problem. You’d just be changing the degree of the problem with a blend knob, blending in and out the out of phase signal. You could do a switch, with an either/or option but I don’t think there is a way to have them both work at the same time. You need a different pup with a compatible configuration. Maybe one with a phantom coil if you are worried about noise (I don’t if there is such a thing in a jazz pup but I seem to recall it from somewhere). Or just a straight jazz and live with the noise. He’s not playing loud or under a lot fluorescent light is he?

    D
     
  12. tuBass

    tuBass

    Dec 14, 2002
    Mesquite, Texas
    well, I have a standard p-bass pickup lying around here. I could make a new pickguard and replace the dimarzio easily enough. Hoefully I will have more luck with it. Any reason why it wouldn't work? This time, since I am going to have to make a new pickguard(again), I will leave enough space for a volume, blend, and a tone knob, or I may just get a stacked knob. Haven't decided yet, but my wiring guy wants another crack at it before we give up on the dimarzio.
    Any other words of wisdom for me?
    anyone, anyone?

    Mark
     
  13. tuBass

    tuBass

    Dec 14, 2002
    Mesquite, Texas
    I talked to a repairman today, and he suggested reversing the wires on the new pickup and adding a stacked pot to separatly control the volume. Darn, I hope I can get this think going, I have spent way too much time, energy and money on a cheap short scale. Oh the things we do for our kids....
    THe neck I got off ebay for it came in the mail today, but I have to get it from the apartment office tomorrow. This thing will be swet when I finally get it together.
    Mark
     
  14. dprives

    dprives

    Apr 22, 2002
    SF Bay Area
    Huh. I would think that reversing the wires would transfer the problem to the d&g strings. But, what do I know. Let us know how it works. I’m interested to see what the effect is.

    Good Luck.

    D
     
  15. tuBass

    tuBass

    Dec 14, 2002
    Mesquite, Texas
    problem solved, but I don't know how he did it. We did add stacked knobs, but there was a phasng problem that was more complicated than switching the wires.

    for pictures, go to this thread.
    "basses" thread


    Thank to all for the help and suggestions.

    Mark
     
  16. Schwinn

    Schwinn

    Dec 4, 2002
    Sarasota, FL
    I was searching for an answer to a problem I have and found this thread...same problem I think TuBass had. Any solutions?

    I have a Bart Jazz and a Bart MM wired using a blend pot and the signal of each pickup is fine everywhere except in the center. It's not the typical out of phase problem because the volume loss is only on the G and D strings. When I installed this stuff I "reverse wired" the MM pickup because, the pickups are definitely out of phase when the wiring instructions are followed. I believed this to be true because the neck jazz I have is really wound to be a "bridge jazz". The pickups weren't bought as a set. Any ideas? FBB you were on it, but how do I fix it?

    If it's not fixable I won't be too sad, since it is only dead center on the blend pot that the problem exists.
     
  17. tuBass

    tuBass

    Dec 14, 2002
    Mesquite, Texas
    I still don't remember what was done to fix the problem, and I've lost contact with the guy who did the work. Sorry.

    Mark