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Thread: Years of Amplifier Hum trouble SOLVED last night!

  1. #1

    Default Years of Amplifier Hum trouble SOLVED last night!

    I have always experienced a very unpleasant HUMMMMM when plugging in ukuleles into my small amps - the Roland Microcube and the VOX Mini.

    For years I thought this must be due to some sort of electrical mismatch between piezo pickups and amps suited for electric guitar.

    But I noticed that my Gibson Les Paul Electric guitar with humbuckers would also hum on my VOX Mini amp specifically, but not on any of my other amps. I initially thought it was because there was something wrong with my guitar, but when I took it to the guitar technician who opened it up and inspected all the wirings, it came back with nothing diagnosed...

    Last night, I decided to try an experiment and used a different power supply plug on my VOX for the first time..

    AND VOILA! NOISELESS AMPLIFICATION.
    On both my guitar AND all my ukuleles!

    I feel kinda angry that VOX would provide power supplies that would cause prominent EMI hum...

    But I feel greatly relieved that a dilemma I've been having for years is solved.

    If you get nasty hum on your amplifier, try changing the power supply!


  2. #2
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    So to be clear, you replaced the entire supply and just didn't fit new the plugs at either end?
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  3. #3
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    I need this advice, kissing. How does one change the whole power supply?

  4. #4

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    Yes, I replaced the entire power supply with a generic one from the electronics store:



    Though the strange thing is, some adapters seem to emit hum more than others.
    I had some other generic adapters lying around.. and they generated hum.

    The one in the picture seems to be the "lucky" one that doesn't generate hum..

  5. #5
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    Thank you, that photo helps. It's incredible that the generic, no name rather cheap appearing power supply made that much difference. Wow. But my amps hum, too, so maybe I'll have to try other power supplies. I think they sell power "conditioners" that change the waveforms from the wall plug or something. Maybe those work, too.

    Rick Turner has always said to monkey with the power supply, as that's the culprit. The power going into the amp. I guess that's right.

  6. #6
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    Thanks for the info. Humm is usually a ground problem and I would typically think it's before the amp.

    Glad to hear a low $$ fix chased the gremlins away.

  7. #7
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    I use batteries in those amps. No hum. Ric

  8. #8
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    I feel kinda angry that VOX would provide power supplies that would cause prominent EMI hum...
    It's highly unlikely that a small power supply like this would generate any level of EMI (electro-magnetic interference) hum, there simply isn't the power available to do so. However, a poorly designed power supply, with insufficient smoothing, or indeed an overloaded power supply (one that doesn't have sufficient power output capability for the job in hand) very often will cause hum. Alternatively, there may be other equipment in the vicinity that is generating EMI and this is being picked up by the power supply and fed to the amp.

    Presumably the original power supply is the correct one for the job and hasn't been interchanged with an inferior unit, possibly by mistake. Does the power output rating on the power supply match the power requirements for the amplifier? If so, I suspect you may have just been unlucky and were supplied with a faulty unit originally Did you ever take up the issue with the original supplier?

    Pleased you've got your problem sorted now
    Last edited by kypfer; 09-20-2014 at 02:34 AM.
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  9. #9
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    I've had good luck with the Danelectro DA-1 power supply. Everyone I bought is quiet. I bought one of the fancy brands, ones with multiple plugs and it hummed. You would think it would be better than the 1/3 price DA-1, it wasn't.

  10. #10
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    From my experience most of the time hum problems come from the power related issues. It could be not properly grounded outlet or faulty power supply. I also had problems with my amp - very loud hum whern instrument plugged in, but when I touched the amp chasis the hum would disapear. The problem was of course on the power side - but when you perform somewhere you never know what to expect on the venue. I have found a solution to that problem - Electro Harmonix Hum Debugger pedal - it just removes hum from the signal, even if it is bad grounding fault, and doesn't change the tone. I always take it with me when I play/perform in unknown place and it saved my life (or rather my tone) many times.
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