Shielding a Jazz Bass

Discussion in 'Hardware, Setup & Repair [BG]' started by audiomann1973, Dec 29, 2012.


  1. audiomann1973

    audiomann1973

    Joined:
    Oct 19, 2012
    Location:
    Italy - Naples
    Hello All,

    this post doesn't want to be a tutorial on how to shield a Jazz Bass there are tons of document online, but is the way I did it.
    Mine is Jap JB that I bought as my first bass in beginning of the 80's, firstly I defretted it then changed the PUs with SD SJB-2 Hot. The instrument has always had little noise, but lately was not playabe at all. So I decided to shield it and redo the electronic with blend pot.
    I have used the aluminium tape, I couldn't find the copper one.

    [​IMG]

    [​IMG]

    [​IMG]

    What I did differently, is the following :

    1) Keep all ground wires separate, from the 2 PUs you can see two white cables. The Electronic is connected direct to POTs cover.

    2) I did not solder the POTs cover as is already on ground, bolted on the cover, this is in order to avoid any loops.

    3) Used simple telephonic cables, white are ground on the right side and red hot on the left side. Routed in this way to prevent any noise induction. Also I have twisted the original cables of the PUs.

    4) Under the mid POT I have bolted a copper connector where I soldered all ground cables, using a single point. Also the jack connection has only the HOT wire.

    [​IMG]

    As capacitor, I have used a Philips 0.047 orange drop good quality one. The schematic I used is the one from SD website.

    In this way I solved the problem, no hum, no hiss anymore even at maximum volume. And I like the blending scheme, having both PUs on the same POT helps me to have a precise tone.

    That's it. Hope it helps someone to fix the noise.

    Saluti
    Francesco
     
  2. DiabolusInMusic

    DiabolusInMusic Functionless Art is Merely Tolerated Vandalism Gold Supporting Member

    Joined:
    Dec 22, 2010
    Location:
    Saskatoon, Saskatchewan
    Looks great, very clean job. Aluminum tape does work but copper works MUCH better (just check the resistance). For future reference you can source copper foil tape locally from stained glass supply shops, I did far too many basses before I learned that.

    I also like to shield the pickup covers and ground them to the control cavity shielding. I usually solder to the cavity shielding, but you cannot solder to the aluminum tape, only copper. I also like to bring my cavity shielding up over the edge so it covers the screw holes, ensuring a nice contact. I have never added a cap for shielding, I am guessing you did it for tone?

    I bet you love that bass even more now, I hate a bass with a hum myself. As far as I am concerned a bass that buzzes isn't stage worthy.
     
  3. audiomann1973

    audiomann1973

    Joined:
    Oct 19, 2012
    Location:
    Italy - Naples
    I could achive 0.8 ohms with aluminium, the connection has been done with the wire on the foil and I sticked another piece of foil on top pressing a lot. I play it LaBella Nylon string, and need a good shield as they are isolated as you know. Normally I use aluminium boxes even when I built tube amps for HI-Fi. I didn't add any capacitor to ground, only the tone one. I also put the foil under the screw hole of the PUs, now the screws are grounded.
     
  4. P Town

    P Town Guest

    Joined:
    Dec 7, 2011
    The statement above regarding not being able to solder to aluminum tape is not accurate. I will be using copper for my shielding work, but I did a test solder joint on aluminum tape, and was surprised at how easy it was to do. I don't remember if I used any flux other than what was in the solder core, but there are "flux pens" available that contain a clear liquid flux, and work almost like a felt tip marker, that I would use to make it even easier. Very little residue left on the work with these pens. Try it yourself.
     
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  6. audiomann1973

    audiomann1973

    Joined:
    Oct 19, 2012
    Location:
    Italy - Naples
    I have tried to solder on aluminium foil, with no luck. But I searched the web and there are some kind of Flux that can do that. I didn't know... there is always something to learn.
     
  7. uOpt

    uOpt Supporting Member

    Joined:
    Jul 21, 2008
    Location:
    Boston, MA, USA
    A couple points:

    You don't seem to have a shield around the pickup wires, that is the way between pickup cavity and electronics cavity. That is a major source of hum.

    You should observe whether the pickup cavity route shielding changes the sound. It can have an effect similar to using a lower value volume pot.

    You can't produce "ground loops" in a guitar that would cause audible hum. But you are right, the pots' cases are best grounded by putting them into a grounded thing, as opposed to soldering to their backs.
     
  8. audiomann1973

    audiomann1973

    Joined:
    Oct 19, 2012
    Location:
    Italy - Naples
    There is no shield on the PUs cables, but are twisted from the source to prevent hum. At the moment I am quite happy with the sound and no hum at all... I am going to leave as it is now. Last thing is, putting some clear nail varnish on the magnets of the PUs.

    Francesco

    P.S. By the way, how would the sound change with shielded cables? More on mids or bass?
     
  9. tabdog

    tabdog

    Joined:
    Feb 9, 2011
    Copper vs aluminum as shielding is one of those
    old arguments that seems to crop up often and I
    have seen no decisive evidence that one works
    better than the other, or that conductance is the
    deciding factor in the effectiveness of shielding.

    For a cheap bass, why go through all that trouble?
    Who's gonna see it anyway? Seems like over kill
    to me.

    To start, I just cram one unbroken piece of heavy
    duty foil down in there and screw a wire to the foil
    and solder the wire to ground.

    [​IMG]

    This usually works and just takes a few minutes
    once the strings are off.

    If that don't do tha trick, then I start looking into
    the source of the problem.

    Over kill is fine for a nice bass. Over kill is fine for
    a cheap bass, but it ain't my idea of time well
    spent,

    Tabdog
     
  10. uOpt

    uOpt Supporting Member

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    Jul 21, 2008
    Location:
    Boston, MA, USA
    What I do is wrap foil around single coil cables (and ground it). The twisted cables still pick up a whole lot of noise, they kind of invalidate your other efforts.

    There is no chance that using shielded wire or another shield around the pickup wires between pickup cavity and electronics cavity changes sound. It is way too short to build up significant capacitance.

    The foil in the pickup cavities (and hence inside the magnetic field) has a much higher chance (because of eddie currents), if you are concerned about sound changes that is what you should investigate.
     
  11. DiabolusInMusic

    DiabolusInMusic Functionless Art is Merely Tolerated Vandalism Gold Supporting Member

    Joined:
    Dec 22, 2010
    Location:
    Saskatoon, Saskatchewan
    uOpt, that is good to know about getting certain flux to solder onto aluminium foil tape, I couldn't get it to work for the life of me.

    Although I will never use aluminum tape again, seriously take an ohm meter to copper foil tape and then aluminum tape, there isn't even a comparison is the resistance values. I don't know why somebody would think there is no difference, I have shielded many basses with both and I can tell you a difference from working with them without even attaching an ohm meter. The cost difference is negligible, maybe a few dollars, and is money well spent. I would also be quite impressed if that shielding job actually worked tabdog, I have never been able to get away with such minimal shielding on any bass I have worked on.

    Twisted cables actually works to do shielding from what I have been told by the folks at kimber kable (I used to run an electronics warehouse, saw a lot of speaker wire reps), and shielding also has zero effect on tone. Do as many side by side tests as you want, there won't a difference. I also have never once shielded the actual wires inside the bass and I remove all the hum every time. I don't even bother twisting the wires inside of my basses.
     
  12. uOpt

    uOpt Supporting Member

    Joined:
    Jul 21, 2008
    Location:
    Boston, MA, USA
    I didn't say anything about soldering the foil.

    I think you are assuming too much here.

    Any conductor, no matter how thin, will do the job equally well. Aluminium is a better conductor than copper, BTW, so your resistance values are more likely to be a result of measuring difficulty.

    If you never shield and don't twist the wires either then there really isn't any point in worrying about which tape to use.
     
  13. Stone Soup

    Stone Soup

    Joined:
    Dec 3, 2012
    Since when?
     
  14. TWISTEDSTRINGS

    TWISTEDSTRINGS Supporting Member

    Joined:
    Oct 13, 2012
    Hi all, I`m having the same hum buzz with my `05 Amer Del Jazz V and just ordered the copper tape(Stewmac is my answer for any and all guitar parts). For those that don`t know they have anything you could possibly need http://www.stewmac.com/ now that I`m done endorsing them I have a question for audiomann1973 or anyone who could answer...I`m a little confused about these ground loops your talking about. Could someone please elaborate on what I need to do with them ? Are you saying separate all the ground wires but run them to one common ground ? Remove all the pot grounds from one another and just ground the cover ? Then make sure that the copper tape is grounded to the common ground ?Any and all help would be appreciated. I`m not to proud to accept a step by step walk through..lol Thanx
     
  15. audiomann1973

    audiomann1973

    Joined:
    Oct 19, 2012
    Location:
    Italy - Naples
    Hello, well I will try to explain as easy as possible step by step what I did...

    1) Put the foil in the PUs cavities , then solder a thin cable of the shield done.

    2) Put the foil in the electronic cavity with a piece of foil outside it long enough to make contact on the chrome POT plate, best if goes up to one screw.

    3) Screw all POTs to the plate and under the middle one put something in copper or brass, where you can easily solder all ground cables. I've used of these :

    [​IMG]

    4) Twist all PU's cables from the source, and run them trough the cavities holes

    5) Assembly all electronic without soldering any ground on the back of the POTs and on the output jack. As all these are bolted on the metallic plate which is the common ground.

    6) Once the electronic is ready, solder the Hot cable of the PUs to the POTs and the groung to the copper part that you have put under mis POT.

    7) Solder the other ground cables coming from the cavities as well as the bridge one to the some point.

    8) Close the electronic part making sure that a good connection is made from shielding copper foil, and check with the multimeter that everything is connected, (Bridge, screws of the PUs and metal plate).

    Something that I haven't done, is to ground the PUs poles, this can be easily done putting a bit of foil under the magnets and connect it to cavity shield.

    Hope I made it clear, but if you help let me know.

    Greetings from Italy and happy new year to everyone!
    Francesco
     
  16. audiomann1973

    audiomann1973

    Joined:
    Oct 19, 2012
    Location:
    Italy - Naples
    Aluminium resistance is around 26 nOhm and copper 16 nOhm. I personally think that if the shield is done in a good way, then the result is good with both metals.
     
  17. uOpt

    uOpt Supporting Member

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    Jul 21, 2008
    Location:
    Boston, MA, USA
    Yeah aluminium is better per weight, not per volume.

    Still, there's no way to get noise through a non-ripped layer of kitchen aluminium foil.
     
  18. audiomann1973

    audiomann1973

    Joined:
    Oct 19, 2012
    Location:
    Italy - Naples
    In fact aluminium is used for High Voltages cables, where is easy to transport for big for big volumes and easy to put in place. Why to use kitchen foil, when the aluminium tape is selling around €5 for 9m by 5cm...
     
  19. uOpt

    uOpt Supporting Member

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    Jul 21, 2008
    Location:
    Boston, MA, USA
    Well if you are concerned about eddie currents then the thinner the better, for the shielding around the pickups.
     

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