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Hum trouble with JP Marcus Miller Jazz Bass

Discussion in 'Hardware, Setup & Repair [BG]' started by Frode Hansen, Jan 17, 2014.

  1. Frode Hansen

    Frode Hansen

    Jan 8, 2014
    Hello, I'm new here and I hope for some help.

    I have quite a problem with hum from my MIJ Fender Marcus Miller Jazz Bass. The amount of hum varies between venues, but the last time I was asked by the sound guy to play another bass because he was unable to hide the noise. It's clearly a grounding issue.

    I've seen articles about totally rewiring the bass, but I'm unable to find them again.
    Are there any of you who have succeded in mending this rather usual problem, or know of any good articles/threads that show solutions?

    Thanks a lot for your help.
  2. Turnaround

    Turnaround Commercial User

    May 6, 2004
    Toronto Canada
    Independent Instrument Technician, and Contractor to Club Bass and Guitar - Toronto
  3. DiabolusInMusic

    DiabolusInMusic Functionless Art is Merely Tolerated Vandalism Supporting Member

    Your bass needs a shielding job, the guide I use is for that particular bass, if you would like a copy PM me with your e-mail, I will shoot you a pdf.

    EDIT: Just clicked the link above, it is the same PDF.
  4. Frode Hansen

    Frode Hansen

    Jan 8, 2014
    Thank you so much, both of you.
    Let's see if I can fix this thing.
    Have a great weekend :)
  5. basskal77


    Jan 14, 2014
    Isn't the first time I hear about hum issue on Marcus Miller Jazz Bass. I think all the electronics on that bass need to be redesigned from the Fender Team.
    You should have a good electronic guy o luthier check the bass and see what is wrong..
  6. f64


    Oct 31, 2009
    Often the most common issue is one pot becoming loose and a leg grounding against something that it shouldn't be touching. I'd check for this first. I've had that issue on both a Fender American Deluxe Zone and a Beck. The MM is similar in having a lot of non-standard Jbass circuitry under the hood.
    A question is also if the hum disappears when you touch the strings. If so take a look here:http://www.talkbass.com/forum/f18/electric-noise-17593/
    If you pop the cover off and don't see something obvious then the best is to have a pro take a look at it. Good luck!
  7. DiabolusInMusic

    DiabolusInMusic Functionless Art is Merely Tolerated Vandalism Supporting Member

    Well by your logic the electronics on %75 of Fender's products are faulty and need to be re-designed. In reality, they are perfectly designed but Fender fails to provide adequate shielding jobs on most of their products. It is an easy fix, it is a shame Fender never does it.
  8. Frode Hansen

    Frode Hansen

    Jan 8, 2014
    Thanks a lot you guys.

    Would you (or anyone else) know of any wiring diagram of this? English is not my first language, and the article does not go in depth of were each wire go. Plus the images are quite small.
    So any elaboration on this would be great.

    Thanks :)
  9. speeves


    Apr 18, 2008
  10. Frode Hansen

    Frode Hansen

    Jan 8, 2014
    Thank you for that, speeves - my bass is not wired quite like that, although the wiring consists of the same components. For example, the little switch features one more lead and a jumper between two of the lugs.

    Could any of you please take a look at that pdf article located here:
    I'm not able to get my head around what it says regarding fixing the ground loops. Does it in essence say that I want to gather all the groundwires together and solder them to the groundlug on the output jack? Or do what he refers to as "signal ground" and "equipment ground" go to different places?

    From what I've gathered, he means putting all the groundwires from the "signal ground" (pickup negative and the lugs on the pots that are soldered to the shell of the pots) together in one bunch, and putting all the "equipment ground" (bridge ground, shield ground and negative batteryside) in another bunch. But do they go to the same point in the end?

    Also, the article mentions wrapping copper around the singlecoils for shielding. Will aluminumtape work as good as copper in that respect?

    Thanks a lot for your input.
  11. DiabolusInMusic

    DiabolusInMusic Functionless Art is Merely Tolerated Vandalism Supporting Member

    Frode, I am not an electrical expert but I have shielded many basses. Here is an extremely simplified version

    1)Line ALL cavities with copper foil (or whatever you chose to use, I recommend copper foil, it can be sourced locally from stained glass supply shops) This includes control cavities as well as both pickup cavities. I personally do not do the battery compartment but it may be required. Line the pickup covers as well, wrap the pickups with electrical tape so they cannot make contact with the copper. I like to bring some of the copper foil around to the outside of the cover, you will see why. Also if the control plate is not metal, line it as well. Ensure the control cavity foil comes up over the edges, I like to bring it over a screw hole so the screw pierces both pieces of foil when screwed down

    2) Ground all copper foil, this means running a wire from each pickup cavity and each pickup cover to a common ground (back in the control cavity, coming from the bridge)

    You can re-assemble the bass now and see if the issue persists, if it does check all connections, including under the bridge. I like to run copper foil tape under the bridge so the ground gets a good connection, this step is usually not needed. Again, I have never had to line a battery compartment, but you might have to, so line and ground that as well if needed. I am pretty sure the fellow who made the mentioned guide does this step but I cannot remember.

    Aluminum foil works just as good but it is really hard to solder to, the extra few dollars is well worth it on copper foil. I did many basses with aluminum tape before I learned stained glass supply stores will carry the product.

    I hope that helps, I will try to keep popping back in if you need help. Please let me know if and when you do remove it, I hate hum and try to remove it from every bass in the world. Basses that hum are not stage worthy instruments in my opinion.
  12. Frode Hansen

    Frode Hansen

    Jan 8, 2014
    DiabolusInMusic, thank you so much for that elaborate guide - I will try that.
    I read another place that someone claims that the ground loop problem on these basses was a myth - that you need two grounds to create a ground loop. He said that the bass only consists of one ground, and therefore it would be impossible to have a ground loop in the bass. He claimed that rewiring the whole thing wouldn't help at all since it all ends in one ground (cable and amp), and whatever improvements would be due to proper shielding.
    I should probably correct myself, because my problem isn't so much 50-60hz hum, it's more like a higher frequency sizzle.

    Again, thank you all.
  13. speeves


    Apr 18, 2008
    could you post a pic of your cavity and wiring?
  14. 96tbird

    96tbird PLEASE STAND BY Supporting Member

    There is only one ground. That comes from the amp via the jack ground. All metal items on the bass need to be touching ground.

    Shielding will help but if your grounds on all items are not good, even the shield won't help. One weak link will mess the entire thing up.
  15. Frode Hansen

    Frode Hansen

    Jan 8, 2014
    Thanks for that.

    Here's my wiring and cavity, hopefully.

  16. DiabolusInMusic

    DiabolusInMusic Functionless Art is Merely Tolerated Vandalism Supporting Member

    Is your buzz affected by you touching metal/strings/bridge? If the noise goes away when touching metal you have a shielding issue, if the noise gets louder you have a grounding issue. If the noise remains constant, you have a deeper issue, but I would first ensure the ground wire under the bridge is making good contact before diagnosing it as a deeper issue.

    I still imagine it is a shielding issue as you can see in the pics, the shielding job is pretty weak to non-existent.
  17. walterw

    walterw Supportive Fender Gold Supporting Member Commercial User

    Feb 20, 2009
    uh, does the noise go away when you turn both pickups up full?

    if so, then none of this is relevant, you're just hearing normal single coil hum.

    also, are you cranking the treble EQ knob way up? that's gonna add a bunch of sizzle and hash too. it's best to be gentle with both EQ knobs, they're both boost-only as i recall and shouldn't be turned all the way up.