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Help! Humming Harman Kardon AVR4550

Discussion in 'AV Receivers & Amplifiers' started by smp, Nov 25, 2003.

  1. smp

    smp
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    I get an audible mains hum through all speaker channels on my new Harman Kardon AVR4500. [-oops it's a 4500 not a 4550 as per eariler post, sorry automatic mental upgrade :) ]

    This happens with no inputs connected, with the volume turned right down to the end stop minimum and even happens when I took it to a friends house (to eliminate any potential RF or mains problem in my house).

    I find it very audible, but I think I'm very sensitive to this frequency band (I can normally hear the hum of a transformer in the room). To me it seems very loud. We also have a small room which might make it more obvious.

    Anyone know whether this is a 'feature' or should I box it up and demand my money back?

    This also seemed to be a feature of my previous sherwood surround processor, I put it down to it being a cheapy model that was slowly going wrong.

    This is doing my head in
     
  2. alexs2

    alexs2
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    Interesting problem,esp.since you've already tried removing all the inputs and even gone to the lengths of trying it in a different environment.

    It's true that there will be a small element of mains related interference on all mains powered equipment,but it should be of a low enough level not to be intrusive.

    Another factor is having very sensitive speakers,which will make background noise and hum more obvious.

    Other than that,it may be worth checking the earthing arrangements on the receiver,and ensuring it is properly earthed,unless it is not earthed(as some receivers,eg. some of the Denons have only a live and neutral supply via a 2pin to 3 pin adaptor plug).
     
  3. hornydragon

    hornydragon
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    You could try getting dealer to swap it with another unit, does it hum if no speakers are connected??? If the unit is not at fault you could try a mains conditioner or similar, if you are sensitive to 50Hz or one of the harmonics then it may be a very worth while investment!
     
  4. smp

    smp
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    The HK isn't earthed, it has a 2 pin like the Denon, I'd already tried a suggestion of earthing the chassis but that didn't make any difference.

    Currently it hums through all of:
    Monitor Audio Silver S1
    Monitor Audio Silver Centre
    Tannoy 663 (my outgoing speakers, though less noticeable).
    JPW Mini Monitors (my outgoing rears).

    However it didn't seem to hum through my friend's Kefs...

    Maybe it is just down to speakers that are senstive in that range? (Unfortunate then that I'm sensitive in that range!).
     
  5. alexs2

    alexs2
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    I think from what you've said that you may well find that it comes down to either your speakers being more efficient than your friend's KEFs,or that your room reinforces the 50Hz hum....you could try moving the speakers around a little and seeing if that reduces the problem to an extent.

    I do also agree with hornydragon's suggestion of getting another receiver from your dealer for a trial.
     
  6. smp

    smp
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    Maybe hum's a little when no speakers connected, certainly a little bit of a tiny thump when you first switch on (I took that to be the transformers). It's the hum through the speakers that drives me wild though.
     
  7. smp

    smp
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    It hums at my friends with my speakers which I took with the unit, I've moved them around a few times as well at home and still get the same effect, have also laid out the speaker cable so that it was no where near any mains cable.

    I think it's looking like a trip to the shop...
     
  8. hornydragon

    hornydragon
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    If it hums with no speakers and volume at low could be a faulty component, you can try loads of stuff but start with the cheapest.
     
  9. alexs2

    alexs2
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    I think you've pretty much exhausted all of the easy cures,and a trip to the shop is definitely the next step....best of luck,as I know how irritating a hum problem can be.
     
  10. smp

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    One other thought? Could it be down to speaker impedance? My new MA's are rated at nominal 6ohms, but my friend's Kef's (which didn't hum, or at least not as loudly) are rated at 8.

    The weighty tome of a user manual for the HK only mentions its power output at 8ohms, it doesn't mention an impedance range for use with the amp.

    (Note that it does hum still with my Tannoys and the other speakers, so maybe the Kef thing is a red herring....).
     
  11. hopefulharmon

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    i also had a problem with hums though all speakers with an avr5500 . b+ w 600 series. what was your outcome?
     
  12. smp

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    hopefulharmon, sorry haven't visited in a while so excuse the delay ahem, in the end I swapped the HK for a Yamaha. I tried another unit and it hummed too. We've come to the conclusion that my hearing is very sensitive to the 50hz frequency band and so I pick it out - I can hear even the quietest transformers. I don't find the Yamaha so 'musical' as the HK, though it does movies very well, so I run the front channels via a pre-out to my existing stereo Amp. The CD-player is hooked into the stereo amp direct for listening to music.
     

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