I hope this is the right place to ask and you guys can help me. I obtain a strange noise, most likely originating from my amplifier. I tried to record it with my phone, so the quality is not really good. Have a listen here.

I am using a Technics SU7700K. The noise is strongest when listening over the phono mode but still notable in tuner/aux mode. You have to put to volume near maximum though. I tried to unplug everything (!) and the noise or signal is still there. I tried to use different power sockets and first I thought is was gone...but then it was back again. I unplugged the speakers and checked over headphones. Still there. I even tried to remove potentially disturbing signals like WiFi or mobile phones. Still there. So...I guess I can safely say the problem is within the amplifier. But I still have no idea what the problem might be. Hope you guys can help. Maybe someone had a similar problem!?

PS: Sorry for my english, it's my second language. If anything is confusing please ask and I try to clarify. Also, thank you very much for your help in advance.

2 Answers 2


Sounds like induction whine to me, certainly not a ground loop, which is always at either 50 or 60Hz, depending on what country you're in.
50Hz can be seen on a guitar tuner as roughly G#, never tested what 60Hz looks like.

Induction whine is generated by some external device, TV, fridge, lighting, even something like a phone or wifi, though phones tend to have a distinctive 'hunting' noise rather than a continuous tone.

Your only real test is to switch off absolutely everything else in a 20m radius & also disconnect all audio peripherals except speakers or headphones, make sure the noise is gone - otherwise it could be self-generated, which would mean you're out of luck - then power up one at a time til you find the culprit.

  • 1
    Well, this sounds like a good idea. And actually I already tried this, but probably not to a satisfying degree. Couldn't find the source so far. But what I discovered yesterday, my guitar amp has the same noise, which kind of confirms that theory of yours.
    – mijc
    Jan 5, 2016 at 10:23
  • 1
    even change the position of the amplifier ( ie rotating it 90 degree ) can change if it is n induction problem Jan 5, 2016 at 11:07

That sounds like ground noise to me https://en.wikipedia.org/wiki/Ground_noise

One way you can check if it's a ground issue is try putting your hand on the amplifier while you listen to the noise. If the sound stops or changes in any way when placing your hand on it, it's most likely a ground issue.

  • Unfortunately, I don't hear any difference in the signal when I am touching the amp.
    – mijc
    Jan 4, 2016 at 19:07

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