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buzzing

Discussion in 'Pickups & Electronics [BG]' started by Mofo-Kang, Aug 29, 2007.


  1. Mofo-Kang

    Mofo-Kang

    Aug 26, 2006
    Modesto, CA
    Rather than continue to hijack that poor guy's thread about drop-in preamps, I thought I'd start a new one for a problem I've run across.

    Okay, I ordered both an Audere drop-in preamp and Dimarzio Ultra Jazz pickups. Both came, and I put them in. Much struggle, much big fight, much pain in the butt, but I finally got all the wiring and battery and everything to fit in the control cavity of my GL J-Bass. Plugged it in, and it works! In fact, it sounds great. One problem: there's a small, but noticable buzzing/humming sound. One that goes away when I touch the knobs or control plate or metal parts of the cable going to the amp. What would be the cause of that? Grounding? It doesn't seem like it'd be a shielding problem (why would it go away when I touch the knobs if it's interference from the electrical wiring in the walls, for example). What do you guys think?
     
  2. Foamy

    Foamy

    Jun 26, 2006
    Sac Area
    Sounds like a grounding problem, like a ground loop. Make sure you only have one common ground.
    One other thing - but DO NOT do this unless someone else here says it's OK. I've read that if one is using a preamp, that some part of this type of buzz/hum can go away.
    I have never done this, and I am not sure if it is dangerous or safe to do.
    That said, I also have an active bass - the Jag - and I do get some buzz when it is active, and it goes almost all away when I touch the strings. I don't get the hum unless I turn on the pre-amp.
     
  3. I had this same problem with my Lakland 55-02 bass at a gig and at my house. I had a razzy buzz that I could not get out of the bass at one of my gigs. As long as I kept my hands on the bass it was alright or touch any metal part on the bass, but as soon as I let go the buzz came back.

    The guys at Lakland said that this was more of a shielding problem rather than grounding. The buzz did not happen at all gigs is why they thought that. They sent me some copper foil shielding to line the inside of the control cavity. This seemed to help a great deal for the most part as I have not had the buzz problem at any gigs since. But I have noticed some light buzz at my home when I get close to those new Swirly light bulbs or a Halogen torch lamp.

    You can find the copper foil at parts places on like guitarparts.com or allparts.com ect. I would just google to find the stuff.

    Best of Luck,
    Ace
     
  4. Mofo-Kang

    Mofo-Kang

    Aug 26, 2006
    Modesto, CA
    I already have some copper foil/tape on order from Warmoth. I guess it can't hurt to try it.
     
  5. That's kinda the way I felt, that I would at least give it a try, but It did make a difference.

    Ace
     
  6. Audere

    Audere Supporting Member Commercial User

    Apr 7, 2005
    South Beach, OR
    Owner: Audere Audio
    I think I already sent you this link but maybe you did not receive it
    Audere Hum and Noise

    Look at the top left of the drawing with human in it.
    What is happening is the power lines are creating noise on your body.
    How much noise? Depends on your environment and actually your body (how conductive you skin is etc).

    Now when you touch the strings you take some/most of this signal off your body.
    It goes though your strings to the bridge grounding wire to the jack to the cable to the amp to the 3rd lug on the wall jack blah blah blah into a rod driven 8' deep in to the ground at your location.

    So the hum/buzz goes away...

    Back to the drawing, on the top right this time, your body is also coupled to your pickups.
    The wood will not stop the coupling.

    So to solve the overall problem you can either
    1) Always be touching ground - not practical in general - sometimes used in a recording studio
    2) Disconnect your body from the pickups by using a grounded shield in-between your body (the noise source) and the pickups

    I suggest shielding the backs and sides of your pickups with that copper tape - this will reduce the noise by removing most of the coupling. The better you shield (really the larger a percentage of area you shield) the more the noise will go away... You must ground the shielding or the problem could be larger not smaller.

    If you have a grounded shield then you will have created the lower drawing with the human.

    More info and measurements etc. is on the web page.

    Good Luck - David
     
  7. Foamy

    Foamy

    Jun 26, 2006
    Sac Area
    Wow, great information! Thanks, David! I'd never thought of or heard of shielding the pickups themselves.
     
  8. Mofo-Kang

    Mofo-Kang

    Aug 26, 2006
    Modesto, CA
    Thanks for the replies everyone. Yes, I got that email from you, David. I just thought I'd ask around a couple of places before I go unscrewing everything again--try to keep the assembly and disassembly to a minimum. :) Thanks for your help, looks like I'll see what the copper foil does.

    I'm also looking around at copper-based shielding paints, which look easier to apply than foil tape.
     
  9. Mofo-Kang

    Mofo-Kang

    Aug 26, 2006
    Modesto, CA
    okay...progress report. I had a bit of a delay because I went and had lasik surgery on my eyes, and so I haven't been working on the bass lately. :) That's okay--it gave me time for the parts to arrive.

    I got the copper tape and paint on the same day, and decided to go with the paint. I double checked the ground wires, and saw that they weren't connected. So I soldered them and THEN crimped them. So the cavities are shielded by copper paint and the ground wires are done up the way they're supposed to be (I hope)...so let's plug it in and check it out.

    Hey, it works! Sounds brilliant, the buzzing is gone--in fact the whole thing is dead silent, even turned up all the way. The Audere and the Ultra Jazz pickups work together very well. I can't play right now as much as I'd like because of my tennis elbow and waiting for the neck to settle in after going for a few days with no strings, but the problems I was having are all fixed. Thanks for the advice, guys. :) And I would highly recommend this Audere if you have a passive J-bass you want to give a little boost to.
     
  10. Mofo-Kang

    Mofo-Kang

    Aug 26, 2006
    Modesto, CA
    Re-reading this thread, I realized I made it sound like the Audere was a big fight and hassle to install. I didn't mean it that way--it was actually fairly easy. What I was referring to with all that drama was the tangle of wires and crap involved in swapping the pickups. :)

    The Audere was actually pretty smooth--the one issue I had was the control cavity being slightly too small for the 9v battery. Also, the way the screw holes lines up, part of the circuit board was coming up against the side of the cavity, making it a tight fit. But we're talking maybe 2mm at most, and 10 minutes with the Dremel shaving the paint down fixed it right up. That problem was with the bass body, not the Audere unit.
     
  11. I just wanted to say a big "thank you" to Dave for the information about noise coupling into (bass) guitar pickups. I've been looking for a long time for a clear explanation and fix for this problem. I'm very excited to see this info (and I'm very curious about the preamp products...)
    I generally don't have a problem with this on my (active) Carvin basses until I attempt to solo one of the pickups. Is the phase wiring of the pickups responsible for the fact that the noise is not present at the output when the pickups are both selected?
     
  12. Audere

    Audere Supporting Member Commercial User

    Apr 7, 2005
    South Beach, OR
    Owner: Audere Audio
    If both pickups:

    1) Have an equal Load
    2) Equal vol
    3) Equal number, size, and shape of windings
    4) Gets an equal sized signal from a noise source

    Then they will cancel at all frequencies.

    1) Is not too much of a problem - unless you have a 5 way Z-Mode switch.

    Sometimes pots will have a lot of variation.

    At a more refined level - your hand is a capacitive load on the pickups and you often will be playing closer too one pickup than the 2nd pickup - all depends on how hard you want to look at the noise levels.

    2) Some cheap balance pots can be really bad...
    I have seen dual balance pots off 20-30% in absolute resistance in the center.

    3) Often causes problems
    Pickups vary a lot from manufacture to manufacture as to how well they cancel - I have seen 12 dB to 40 dB.

    In general, the very uniform machine wound pickups on plastic bobbins cancel the best. Often these are not considered ideal by many players.

    As the frequency gets higher most pickups are less identical to each other...

    4) This only happens when you bass is directly facing the 1 noise source which is a "long" distance away. But that 1 noise source is not allowed by electrical code... you have to have x outlets per Y space of wall etc.

    This is why if you listen you can rotate a bass around and get different levels of noise. You could use the "old style" metal enclosed cabling (like you see on the surface of some walls) and kill the noise from the wires in the wall but no one does because this is too expensive. If I were going to build a special sound studio I would spend the $s to do it.

    Same thing happens with hum buckers as 2 separate pickup but the 2 coils are located much closer together so they tend to get the same signal more often.

    The out of phase connection does help but it would be better to remove it from each pickup coil...
     
  13. bgartist

    bgartist Supporting Member

    Feb 4, 2004
    Chicago, IL
    I have the same problem on a Lakland DJ5 I just installed an Audere in. Thanks for the info!
     
  14. bgartist

    bgartist Supporting Member

    Feb 4, 2004
    Chicago, IL
    My DJ5 had no shielding at all. I lined the control cavity with copper foil tape-dead silence. Thanks for the tip!!!

     
  15. Mofo-Kang

    Mofo-Kang

    Aug 26, 2006
    Modesto, CA

    Is it a big pain to use that foil tape? I got some along with copper shielding paint, and wound up using the paint because it looked easier.
     
  16. dives

    dives

    Sep 3, 2007
    I've posted a couple of threads about this problem...cause i couldn't find one earlier...anyway had no replies. I was real happy to find this one. although I shielded the control cavity of my custom built bass, I never thought about the pickup cavity. I'm gonna try that this weekend...hope it works.
    Thanks for the tip(s), guys.
     
  17. bgartist

    bgartist Supporting Member

    Feb 4, 2004
    Chicago, IL
    It was very easy. Completed in 5 minutes.

     

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