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How can I cut out 60hz reception from transformer?

  1. Sep 26, 2013 #1
    I just made an amp for a friend giving about 30 watts x2. but it is in a small project box and I am recieving 60hz coming into the input of the amps.
    I have done tests and it is the EM field of the transformer, I have 2 trimpots on the inputs to the amplifier and have been able to cut out this hum but not without losing some volume along with it.
    Is there any quick and easy way to fix the hum?
  2. jcsd
  3. Sep 27, 2013 #2


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    Gold Member

    Transformer orientation can sometimes help. Not sure about mu-metal at 60Hz (I've used it for crosstalking audio transformers).

    For the EM field to cause hum it needs to be induced into a loop somewhere. Maybe you can reduce receiving loop size. Twisting wires , etc.

    It's possible that there is 60 Hz in a ground loop and moving the transformer cancels it out?

    I'm just saying what comes to mind, of course.
  4. Sep 27, 2013 #3
    yes thank you, I have been able to cut most out by shortening the input wire configuration, but when I make amps I set the amplifiers gain very high and have a trim-pot on the input because you will get MUCH better sound quallity when amplifying small signals, so I am just going to lower the gain a bit ,

  5. Sep 28, 2013 #4
    do you have any picture of your box amplifier setup?

    I have build a few too and usually it's not that the transformer is not filtered enough it is that the field of the transformer literally induces the frequency to the amplifier and so there is this buzz.
    Basically there are either two things , put the transformer further away or make a cage for it.Basically that doesn't help much atleast in my case.
  6. Sep 28, 2013 #5
    You might try operating your amp on battery to see if the hum is still there. If so, it's probably in the power supply. Also try shorting the inputs to see if it goes away.
  7. Sep 28, 2013 #6


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    To check if it really is getting onto the input to the amp, touch one of the input leads with a screwdriver while holding the metal part. It the hum gets louder, that's where it's getting in. If nothing changes, you probably need to redesign your power supply to improve the smoothing.

    Note, that test assumes your amp is designed and built following good safely practices - I take no responsibility for what happens to you if it's not!
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