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my amp is a radio

Discussion in 'Amps and Cabs [BG]' started by fretbuzz, Nov 27, 2002.

  1. ok, whats the best way to stop my amp from picking up local radio? btw, its an old tube fender and i can hear radio with or without my bass plugged in, thanks for your help.
  2. FretNoMore

    FretNoMore * Cooking with GAS *

    Jan 25, 2002
    The frozen north
    I don't know anything first hand about this, but a quick Internet search gave this up (from http://guitarrage.virtualave.net/amplifiers/repairs/fault_finding.html):

    Symptom: Radio signals can be heard through the amplifier.

    Cause: Radio interference is normally from radio stations in the AM band. Electronic circuits are notorious for picking up stray signals, especially active circuits.

    Solution: The first thing to do is make sure that it is the amplifier and not the guitar. If it's the guitar, then try shielding the guitar. If it's definitely the amplifier. You should check that all of your amplifiers grounds are connected properly. If they are, you can try soldering a 10 to 100pF capacitor between the HOT input lead of your amplifier and ground. This will shunt radio frequencies to ground. If this still doesn't solve the problem, it's a job for the local technician.
  3. arizonabass


    Feb 6, 2002
    Tucson, AZ
    As Anders says, it's really a job for a technician, but only one who is well versed in Radio Frequency Interference (RFI). You didn't say whether or not your instrument CORD is plugged into the amp while its receiving radio signals. ?
  4. NO, the cord is not plugged in.
  5. Yikes. It's usually the guitar cable that's the cause.

    Ok, so have you flipped the Polarity switch to see if that helps? If not, then probably time for a tech.

    Have you tried tying a knot in the power cord? Slight chance that that might help.

  6. THANKS, ill try the knot. and yes ive tried to switch the ground. i think that in my area, we have a local radio transmitter so it might be something that i have to live with. is it possible that a power conditioner might help?
  7. arizonabass


    Feb 6, 2002
    Tucson, AZ

    Go to this website. This company has a good reputation for their filters. They sell an AC line filter, which *might* help, but you will have to somehow determine whether or not the signals are coming in through the AC line. (Radio Shack also sells an AC line filter. Typically they will let you return it if it doesn't "work.") If not, then it could be a "simple" case of what's called fundamental overload. That would typically occur if the transmitter is relatively close to your amp, say, maybe a few blocks away. I have another suggestion: Move the amp to a different room and see what happens. The AC lines could be acting as antennas - even your power cord could be acting as an antenna. Here's another suggestion: Plug your power cord into an extension cord and see if "extending the antenna" changes anything. You may need to go through quite a process to eliminate all possibilities until you are sure you have found where the signal is coming in. At the worst, you may have to physically shield the amplifier itself.
  8. thanks, ill work on it this weekend

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