single coils noise

Discussion in 'Basses [BG]' started by mellow yellow, Dec 3, 2013.

  1. Hi from Italy,
    the title of this thread maybe it's incorrect, but anyway I'll try to explain.
    I have a beautiful 1961 fender jazz custom shop, stacked knobs and that horrible brass flatwire ground junction from the bridge pickup to the bridge itself.
    When I use this bass with my Epifani Ul501 there's a sort of electrical noise, with mainly high frequencies. It's annoying, a couple of days ago I was playing with a big band and when the conductor was speaking to the audience I had to engage the mute button of the Epifani. I don't think that is the single coils hum (I mean I have that hum and I can hear it when I lower the volume of one pickup, but this is a low freq noise) anyway I have this situation:
    1961 fender jazz with ul501 = noise (in studio where I have a good ground connection and without TV and any sort of RFI, live concert, and so on)
    1961 fender jazz with ebs classic60/Acoustic 115 = smaller amount of noise than with the Epifani
    lutherie jazz bass with bartolini hum cancelling with ul501 = no noise
    So I'm thinking that for sure single coils are prone to capture RFI but also the UL501 could be the guilty, and this is very bad because the Ul501 is a very good sounding amp.
    any suggestion?
    thanx in advance and sorry for my english
  2. The Bass Clef

    The Bass Clef Formerly "thebrian" Gold Supporting Member

    Nov 17, 2010
    You may have a ground wire that came loose somewhere. I'd check to make sure that the bridge ground strip isn't dug into the wood and check that it is still making contact with the bridge. Then make sure that strip is still connected to the ground plate under the bridge P/U. Then make sure that the 2 P/U ground plates are connected to the control cavity ground plate. And lastly, make sure the control cavity ground plate is connected to the casing of one of the pots. That's about all I can think of that could make the sound you describe.
  3. WoodyG3


    May 6, 2003
    Colorado, USA
    Are the pickup and control cavities shielded? If not, shielding has made a huge difference for me with several basses that I have owned.
  4. Today at a repair shop, with my 1961 fender jazz custom shop connected to my UL501, there is a loud noise, lowering one of the pickups there is another noise summed at the first noise, the typical hum from the pickups non hum canceling. The tech inspected the bass, but nothing bad about soldering and so on.
    If I put my hand on the strings the bass is quieter. If I lower the volume of the two pickups at zero the noise is present, at the same amount if I set the two volumes at full. This is strange, because with another bass, a passive P, the noise is presents, but with the volume of the bass at zero the noise disappears.
    The tech says that could be a problem regarding the use of the ul501 with this type of bass, the UL501 switching transformer seems to be picky about high frequencies and so it starts to oscillates with only 50% of gain, with the pot at "twelve" or mid position, if I increase the gain the preamp section of the head goes in overload, with the bass connected but without playing any note.
    So the guilty seems to be the uL 501, but this fabulous sounding head works very well with active basses and well with passive hum canceling basses.
    For strange that it could be, right now the words of the tech they seem something quite truthful.
    A strange situation, but returning to home I was thinking if the pursuit of the single coils gorgeous sound is worth all these things.
    I'm just depressed about this situation, both fender jazz and the ul501 are beautiful instruments and I don't want to sell one of them.
  5. Scottkarch


    Sep 11, 2012
    I have a number of single coil basses that will hum when in certain places. I purchased a Hum Debugger and it works fantastic. It uses AC power, ( it's a AC step down power supply, not AC to DC... it's labled AC-AC ).. this way the device knows and can follow the AC sine wave and know how to eliminate the additional frequencies correctly. I cant hear any lost signal, just a loss of the HUM. I put it first in line from my bass...

    Bass - HumDebugger - compressor - amp.

    I don't know if other have used this, but I highly recommend it.

  6. Dbassmon


    Oct 2, 2004
    Rutherford, NJ
    Single coil pickup are susceptible to noise. They are noisy but they sound great, aggressive and forward.

    As other suggest... improve the shielding of the bass, power conditioner can help clean up noise coming for the AC power source... play with both pickups up...they become humbucking.

    You are going to have to deal with some noise if you like single coil pickups.
  7. ok, so today a brief check with a simple fender rumble 25 and my non hum cancelling single coils 1961 fender jazz custom shop and my lutherie clone with hum cancelling bartolinis.
    the only difference between the two passive basses was the hum that started when I lowered one volume on my 1961, besides this, the noise was identical in terms of loudness.
    So this drive me to think that the guilty could be the ul501.
    Luckily the tech has charged the head for an assistance duty.
    The only thing that comes to mind, in this strange situation, besides some failure in the ul501, is that the pickups of the 1961 fender jazz custom shop could be turned to have microphonic issue, but the bass it is barely two years old and it's quite impossible.

    I'll tell you when I'll know more.
  8. bassbenj


    Aug 11, 2009
    First you need to discover the kind of hum and noise you have. Does the noise change or go away when you touch ground? If so, then it is a shielding problem. And it means the bass needs internal shielding (or the ground on the intermal shielding is disconnected). Copper foil is best in my opinion.

    Single coil hum (which also can pickup high frequency noises from electronic supplies, dimmers etc.) acts as you are already aware. It tends to go away when both pickups are on full, it does NOT depend on touching the strings (ground), and will vary with the orientation of the bass where if you move it around just so (not necessarily a playable position) you can find a sort of "null" where noise is minimal or gone.

    And lastly there is RF (radio frequency) noise which gets into amps. It's really an amp problem. Sometimes you can actually hear radio stations. It's tricky stuff because this noise can actually travel down the OUTSIDE of the cable! The standard fix for this noise (or should I say the first thing to try because it can be a nightmare to fix) is 100 pico Farad caps solder across the bass output jack and the amp input jack. Those are supposed to shunt noise to ground but are small enough as to not effect tone.

    Once you figure out what kind of noise it is you can start to take steps to eliminate it. One answer that may or may not be easy is to just change your location away from the noise source whatever it is.
  9. MVE


    Aug 8, 2010
    Well, it sounds like you have definitely isolated it to the amp. (I am assuming you have already tried different cords...)

    Could be any number of things inside the amp, a cold joint somewhere/anywhere can easily introduce a hum.

    Your tech will find the hum on his scope and work backwards along the signal chain to isolate it and try to determine what the problem is.
  10. many thanks to everyone. I doubt that a fender custom shop could needs a shielding job in the cavity, I'd tend to not modificate the bass, first of all when it is in full warranty. The tech spoke with the shop owner and the latter was kind enough to give him another ul501, a new one, to check with my fender.
    It's strange, but I have the suspect that the guilty could be the bass, a sort of microphonic issue, the ul501 preamp section goes on overload if I set the gain pot over the half.
    I'll check my fender with the 2 Ul501 side by side and I'll tell you something more.
  11. MVE


    Aug 8, 2010
    How close to the amp are you standing???

    If you are standing within the magnetic field of your transformer (within 5ft or so) then you will introduce a hum that is separate from the standard single coil hum.
  12. BlueTalon

    BlueTalon Happy Cynic

    Mar 20, 2011
    Spokane, Washington
    Endorsing Artist: Turnstyle Switch
    The side-by-side amp test will be useful.

    When did you buy the bass? Do you not want to modify it only because of the warranty? If you don't want to modify it, that will limit your options.

    I recommend shielding it. I also recommend switching pickups from single coils, to hum cancelling dual-in-line single coils, such as the Bartolinis in your other bass. There are many companies that make such pickups -- I have Fender super 55 pickups in my bass (the one in my avatar), and I love the sound of them.
  13. Jim Carr

    Jim Carr Dr. Jim Gold Supporting Member

    Jan 21, 2006
    Denton, TX or Kailua, HI
    fEARful Kool-Aid dispensing liberal academic card-carrying union member Musicians Local 72-147
    Hi Roberto—
    I have a '61 duotone Custom Shop Jazz Relic. I have not had the problem you describe. I love this bass, as you must love your bass. I wish I could offer some help, and am hoping you isolate the problem to be an easy repair needed in your Epifani amp. BTW, I have 3 Epifani cabinets, and they are very good. Keep us informed! :cool:
  14. Roberto, unfortunately most of us are from the U.S. and our electrical power is 120v 60Hz. Yours is 230v 50Hz. Because of that, you may experience specific issues that we might not experience with exactly the same equipment. I don't know if the higher voltage mains may lead to the possibility of more interference than our 120v, or if equipment (like your amp) that is designed to be used with either voltage may actually be more susceptible to such issues with one voltage source than the other.

    Perhaps some of our U.K. friends have some info here. Or what about you Aussies or Kiwis???
  15. Thanks Jim,
    this is the 3rd CS jazz bass and I'm absolutely sold on it, hey it's a 1961 my birth year ah ah ah
    Anyway I hope to solve my problem because I don't want to sell neither the bass nor the head.
    I have this Ul501 and a DIST 112 cabinet and, besides this problem, I'm very happy with this rig.
    Mark Bass, Epifani, Bergantino, these days it seems that for bass amplification italians do it better ah ah ah
    I have to admit that I've owned a Mesa Boogie Walkabout and that was a built like a tank head, unfortunately it was too rock oriented for my taste so I sold it. Epifani is more comfortable to me, I play jazz and fusion either in big band than in small combos, so a clean but somewhat tone is requested.

    What is Duo Tone?



    Attached Files:

  16. ...ehm somewhat FAT tone is requested, sorry for my scholastic english
  17. Jim Carr

    Jim Carr Dr. Jim Gold Supporting Member

    Jan 21, 2006
    Denton, TX or Kailua, HI
    fEARful Kool-Aid dispensing liberal academic card-carrying union member Musicians Local 72-147
    Roberto—as we know, ALL music is "in Italian." :D

    The duotone CS basses are just called that because they are built from three planks (wood boards). An Alder wood plank is in the center, and the side "wings" are Ash wood. Why? I don't know, but I like the sound of my instrument very much. :D
  18. Jim Carr

    Jim Carr Dr. Jim Gold Supporting Member

    Jan 21, 2006
    Denton, TX or Kailua, HI
    fEARful Kool-Aid dispensing liberal academic card-carrying union member Musicians Local 72-147
    I am playing Big Band Jazz, too, but use mostly upright. Here is a pic of my CS Jazz with my oldest Epifani cab: Jim's%20CS%20Jazz%20relic_1.
  19. beautiful bass, is quite similar to mine, mainly in the electronic side, I mean stack knobs. They are more versatile than the vol vol ton circuit, but more difficult to operate, especially in live situation. When I lower the neck pickup volume, to play over the bridge pickup, jaco sound, I end to unintentionally move also the tone external knob.
    I didn't know the Duo tone thing, very interesting. For sure it has to have a particular sound. About fender CS replicas I don't like at all the bridge, too thin, and the machine heads, not smooth as schaller or hipshot. They are era correct but they lack in functionality. In the near future I think to upgrade them.