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Star Ground and Shielding works!

Discussion in 'Pickups & Electronics [BG]' started by superfly, Dec 26, 2004.

  1. superfly


    Aug 4, 2004
    I picked up a Mexi p bass at GC a few days ago, black w -tortoise pick guard( I changed it out), I also changed the p'ups to Duncan Vintage basslines.
    I wanted to get rid of that annoying hum, buzz that happens when you dont' have your hand on the strings or knobs. I checked out the procedure at the "guitarnuts " website concerning star grounding and cavity shielding.

    I used the aluminum tape method (home depot) to shield the control cavity and the pickup cavity, star grounding method, and I shielded the entire back of the pickguard with aluminum foil.

    I'll be darned, it worked! The bass is totally silent now whether I am touching the bass or not.

    Also, I can't say enough good things about these Fender Mexi P basses. They are relativley cheap (I paid $325 out the door), they stay in tune, and they adjust well. Its the 2nd one I've owned, and they have both been fun to play and mess with.
  2. RyanHelms


    Sep 20, 2003
    Cleveland, OH
    Welcome to the fold my shielded, star grounded bretheren.

    (too much?)

    The only thing to be aware of with the hardware store aluminum tape is that it's backed with non-conductive adhesive. The only way to assure that the pickguard foil is part of your grounding plane (it's still doing it's sheilding job, though) is for it to make contact with that piece of cavity foil that's directly sharing the star ground lug. Know what I mean?

    Sounds like you're good to go, regardless, if the bass is quiet now. Isn't it wonderful putting it back together, plugging in, and your bass is completely quite? And you did it yourself!?!?!

    Myself, I like to do a little dance. :hyper:
  3. pdusen


    Aug 18, 2004
    I have a problem with star grounding.

    My Ibanez GSR200 has a bit of a humming problem when I am not touching the strings, tuners, or bridge. From what I've read, I figure it's a grounding issue.

    My dad and I opened up the cavity a few days ag and found (thank the gods) it was already shielded with some form of aluminum foil. Which takes care of that.

    I have two issues with star grounding. First, the guitarnuts guide is made for stratocasters, and I'm having a HELL of a time trying to figure out how it would apply to my Iby.

    Second, we gave it a twice-over, and my dad and I can't find any way we'd be able to ground the bridge in any case. There is no hole or route leading from the bridge to the cavity. I would really, REALLY hate to drill holes in this bass.

    Can anybody help me?
  4. RyanHelms


    Sep 20, 2003
    Cleveland, OH
    The concept is pretty straight forward - anything that's supposed to connect to ground should do so on it's own wire and all those wires should meet at a ring terminal attached to the inside of the shielded control cavity. This then makes the foil's job twofold - to shield from RF, and establish a grounding plane.

    As for grounding the bridge, the jury's still out. Check out this thread - it tends to get off the subject of quiting your instrument, though, and more into how to avoid electrocution should there be an equiptment failure... You may find that star grounding (done correctly, with good shielding) eliminates hum.

    Drilling for a bridge ground is really not that hard, even though you might want to hold your breath while you're doing it ;) Use a 12" long 1/8" drill bit and make sure the angle is shallow enough that you'll come out in the control cavity and, um, not the back of the bass. First, sink just the tip of a larger bit straight down, that helps to get the angle started. I have yet to drill out the back of an instrument. (now that I said that, the next one will probably come right out the back...)
  5. A9X


    Dec 27, 2003
    Sinny, Oztraya
    Congrats. Another convert.

    Recently a workmate gave me her guitar to change the output jack, and commented in passing that "it's always been noisy", like that was SOP for all guitars. When I looked inside the cavity, I could see why; the factory wiring was a dogs breakfast. Now this was a vintage instrument, so I removed everything except the pickups* and replaced the pots, jack and wiring with a star earth setup. I also soldered up a little brass 'shell' the shape of the cavity and made an acrylic cavity cover with brass sheet glued to the inside to complete the box. The pots were Spectrol and Bourns and the jack Switchcraft. It's now silent.

    * all the wiring/pots were removed as an assembly, so with about 6 solder joints, the whole lot could be reinstalled as it was to make it 'authentic vintage'.
  6. todd 4ta

    todd 4ta

    Apr 3, 2003
    Sadowsky bass preamp installs (and Nino's too) are great examples of a star ground. I'm curious though that the wiring diagram for the onboard Sadowsky preamp tells you to solder the ground wires to the back of the treble pot lug.

    Hey Nino, if you haven't done it before can you post a wiring diagram for one of your installs with star ground (preferably an OBP-1 with vol-pan-treble-bass, that's what I'm doing right now).

    What are you using for the eyelet that everything grounds to?
  7. RyanHelms


    Sep 20, 2003
    Cleveland, OH
    Do tell. I like audio quality ring terminals (gold plated look real spiffy), with the crimp connection spread apart. It's perfect to hold a tidy pool of solder for all the ground wires. The only bugaboo is if it ever needs re-worked, a 30 watt iron takes forever to melt that since the ring terminal, all the lines, and the foil are sapping the heat...

    Say Dharmabass, you wouldn't happen to be on Her Majesty's side of the pond, what with the "earth" reference? I remember first seeing that in a manual for one of my VW's, something about "confirming a solid connection to earth" and I'm thinking "yea man, all four wheels are touching the ground"... :rolleyes:
  8. A9X


    Dec 27, 2003
    Sinny, Oztraya
    We're still in the Commonwealth, but I try not to think of it that way; Australia.
    Well, you're obviously not driving fast enough. Oops, sorry, forgot you mentioned it was a Volks.......
  9. RyanHelms


    Sep 20, 2003
    Cleveland, OH
    LOL! True, true ;)

    Back on topic - snipping open the ring end of a ring terminal so it can slip under a pot or under the inside nut of a long shank output jack is a quick and easy alternative to actually screwing the terminal to the inside wall of the control cavity...