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Preamp in my G&L L-1500 picks up a radio station!

Discussion in 'Pickups & Electronics [BG]' started by bassdude51, Jan 8, 2012.


  1. bassdude51

    bassdude51 Supporting Member

    Nov 1, 2008
    Central Ohio
    I've searched through TalkBass and can't readily find info on this problem. I tried! (I can't remember where I read it but others have had this same problem too.)

    I just bought a used G&L L-1500, year 2000 and when I turn on the preamp switch, I can hear a faint radio station. The preamp really kicks up the treble to an extreme level and when I take it down, the radio station pretty much can't be heard.

    The radio pick up is worse when the G&L's pickup is in parallel and less when in series.

    When the preamp is off and the bass is in passive mode, there is no radio noise.

    I noticed that there is ZERO shielding in the cavity. Nothing! Would shielding paint, copper, brass or aluminum inside the control cavity get rid of the radio noise when the preamp is on?

    I don't want to modify this bass (for reselling purposes) with shielding unless if it'll clear up the radio noise. Seems strange G&L didn't do any shielding!

    Thanks for your help.
     
  2. SGD Lutherie

    SGD Lutherie Banned Commercial User

    Aug 21, 2008
    Bloomfield, NJ
    Owner, SGD Music Products
    Yes, shielding would help a lot.

    Another thing to try of that doesn't fix it is to get a small value capacitor, like 15-20 pF, and connect that between the input of the preamp and ground. That should shunt the RF signals to ground.
     
  3. Sorry I can not help on this one. However I did get a chuckle out of this, sorry. Reminds me of spinal tap!!
     
  4. Alternatively, you could use this to your advantage.

    Find out exactly which frequency your bass picks up. Buy a small hobby RF transmitter made for the FM frequency range (if it is, in fact, in the FM band... you could get an AM one, too, I guess) and set it to that frequency.

    Record your bass lines PERFECTLY and arrange them in your band's setlist with the appropriate pauses and whatnot that normally happen during a live show.

    Now here's the good part: Bring a small .mp3 player and load it up with your bass tracks. Hook it up to the radio transmitter during a gig and keep it nearby - the nearby transmitter's signal will wash out the signal from the faint station it picked up before. Turn on the preamp, flip the switch to parallel. Sit back and relax and do your best playing air-bass while the pre-recorded tracks flow from your bass' pre-amp to your amp, sounding *just like* your playing.

    Continue to drink past your level of playability or... just fall asleep. Maybe focus on stage presence and don't worry about getting the notes right! Run, jump, throw your bass through the air - whatever!
     
  5. kellyrojo

    kellyrojo

    Feb 16, 2011
    South Carolina
    when you solve this problem let us know how ya did it! Thanks!
     
  6. I had the same problem on my L1500. Shielding does the trick, in passive mode the bass is dead quiet and even in active-parallel with the tone open wide, the noise is now negligible.

    I wonder why a brilliant company like G&L doesn't use any shielding, it would seem like the obvious place to get ahead of the competition. I had it done cheap, but in a way I feel like a premium instrument should be complete from the purchase.

    Martin
     
  7. SGD Lutherie

    SGD Lutherie Banned Commercial User

    Aug 21, 2008
    Bloomfield, NJ
    Owner, SGD Music Products
    Same reason Fender and Music Man didn't. No shielded cables either. I guess Leo didn't think it was needed.

    They they rigidly stick to tradition. Fender now does some shielding, but it's generally not executed well. I don't know about the EB MM basses.
     
  8. willsellout

    willsellout Supporting Member

    Aug 13, 2002
    Fort Wayne, IN
    My recent L1505 has a layer of paint in it but that's it. I shielded the cover. I'll probably take everything out and finish the paint job on it at some point. Although it's pretty darn quiet right now.
     
  9. Yeah, that's my assumption as well. I think that G&L, being the least well known of the Fender brands, might have established themselves as the perfect blend of tradition and progress, but when it comes to shielding they miss out on easy points. Silly, if you ask me.

    Martin
     
  10. bassdude51

    bassdude51 Supporting Member

    Nov 1, 2008
    Central Ohio
    G&L L-1500 radio interference has been completely removed!

    Thanks to all of you that gave me advice to shield the control cavity.

    Saturday, Jan. 21, 2012, I took off the mounting hardware for the pots and switches and had to unsodder the output jack. I lifted all of this out of the cavity and laid down adhesive aluminum tape insided of the cavity, totally covering everthing including the black plastic cover plate.

    With a voltmeter, I tested for electrical contact of all over lapping pieces of the aluminum tape that were used to cover the inside cavity. It's important that all pieces have metal to metal contact because the back side of the aluminum tape has a thick adhesive that hinders electrical contact.

    Success! The L-1500 no longer picks up the annoying radio station when the pre-amp is turn on! Dead quiet!

    It was worth the effort to shield.

    Thanks to all of you TBers for your advice!
     

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