Receiver transformer hum?

Discussion in 'AV Receivers' started by Richard Moya, Apr 24, 2003.

  1. Richard Moya

    Richard Moya Stunt Coordinator

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    When I power up my DA2ES I find a very, very low pitched transformer hum coming from the unit. It is barely audible, but I was curious if that was considered normal. The unit gets quite warm when watching movies. I wonder if the 2 are tied together. Other than that, the unit works great and I have no problems. Can someone please help?
     
  2. Chu Gai

    Chu Gai Lead Actor

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    from the unit or from the speakers? If the latter, disconnect the tv cable from the unit entirely and see if the hum goes away.
     
  3. Yogi

    Yogi Screenwriter

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    If from the unit then dont worry about it if its not audible from seating position. I am not sure how many components around the house would be having transformer hum of we stuck our ears to every one of them. Its normal.
     
  4. Arthur S

    Arthur S Cinematographer

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    Richard

    The transformers in some receivers hum and other receivers do not hum. Ideally you should not hear any hum at all. On the other hand, you will rarely if ever hear the hum when you use the receiver. If the hum really bothers you, and you are within 30 days maybe you want to rethink the Sony.

    Artie
     
  5. JackS

    JackS Supporting Actor

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    Its normal. Most amps and receivers will hum if you listen closly enough.
     
  6. Chu Gai

    Chu Gai Lead Actor

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    Sometimes, one can lessen the severity of such a hum.
    You could try placing the unit on something absorbant like a piece of soft carpeting.
    If you're willing to open the unit up and this isn't an issue with voiding a warranty, you can take a look and see how the transformer is attached to the chassis. If it's screwed down tightly, then adding isolation grommets may solve the problem. On the other hand, maybe the nuts holding it down are loose.
    Depends on how comfortable you are with going inside. The thing about noise, is once you know it's there, you zero in on it all the time. Kind of like a piece of nut stuck in your teeth [​IMG]
     
  7. Brett DiMichele

    Brett DiMichele Producer

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    If they would all use torodials encased in epoxy and steel
    we wouldn't "hear" about this problem any more.. And yes..
    The Pun was intended! [​IMG]
     
  8. Shiu

    Shiu Second Unit

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    My DA4ES hums even louder. I am sure I could quiet it down a little if I open it and do something about the mounting but I am not going to bother. I went to a high end hi-fi store and listen to a few top of the line Pioneer and yamaha products. They hum just as loud, so I thought this must be normal. Interesting enough I owned a DA1ES before, I could hardly hear the hum, same for some entry level Yamaha, the hum is much quieter than the huge high end one. I wonder if the larger transformers hum louder. By the way, people like to talk about ground loops and stuff like that, that kind of hum are usually much louder and you could hear it from the speaker. Receiver transformer hums are generally audible only if get close to it.
     
  9. Brett DiMichele

    Brett DiMichele Producer

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    FWIW my Onkyo Reciever and Power Amp do not hum. The only
    pieces I own that exhibit Transformer Hum are my tube amps
    and it's no wonder since the primary tranny is 340Volts and
    the secondary is large also.
     
  10. Shiu

    Shiu Second Unit

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    I would like to make one more point. I posted here before about my Sony DA4ES hum. A few people reported back saying that they heard no such hum. So I thought mine must have a transformer that has a loose core, or something like that. Then I went to several stores, including a high end one. I found that when I and a 2nd person,(obviously very reluctantly, but on my insistant) put our ears closed to those receivers that cost more than the 4ES, we heard similar hum, probably even louder considering the ambient noise inside the store was higher than that in my house. In fact, the two models that I mentioned was listed at prices that double that of the 4ES. After that, I stopped complaining about the 4ES. I know if I could not stand the hum (that is not noticeable unless you zero in on it and get really close to the thing), I could always go back to the 1ES. I am sure the 1ES hums too, but it obviously was quieter because it never attracted my attention. My point is, as someone else mentioned here, if you put your ears close enough to a power supply transformer (including toroidal), you will (I mean should....) hear it. The noise level will have some variability among different models, the type, and the size of their transformers.

    So, Richard, if you want to feel better about your 2ES, go to some hi-end stores and pick on say a Pioneer 45 or 49TX (not sure if I got the number right) that has a list price of at least $1,500. Make sure you put your ears very close to the chassis and that the room is quiet. Your 2ES and 4ES are great receivers for the money.
     
  11. James Edward

    James Edward Supporting Actor

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    My NAD T752 has a transformer hum also. It is not noticeable from my seating position, so I have decided to leave it alone. When I first heard it, I was annoyed, now I just don't care. My Adcom 5800 250wpc stereo amp has a transformer hum when certain other things are on in the house. Especially the humidifier... otherwise, it's quiet.

    Ironically, any cheaper equipment I've ever owned never had a transformer hum.
     
  12. Shiu

    Shiu Second Unit

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    Whether your equipment hums or not, you may be happy to see others story about it by google searching "transformer hums" or "transformer hum". If yours hum you will feel better to know you are not the only one, and that it is normal. If yours don't hum you will feel good and lucky.
     
  13. Yogi

    Yogi Screenwriter

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    It is the nature of transformers to hum so dont worry about it.
     
  14. Mike Up

    Mike Up Second Unit

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    It depends. My Yamaha RX-V793 never had transformer 'buzz'. My Yamaha RX-V995 upgrade had a noticeable buzz, but that was when only inches from it. Otherwise it wasn't heard. The Yamaha RX-V2095 upgrade was 'dead' quiet. No transformer buzz at all, as with the RX-V793. My Denon AVR-3803 has no transformer buzz at all, but has a very high pitched(15Khz?)hum that can be heard if about 5" away. Further away it's unheard. I think this is due to some other electronics but I don't know what.

    All receivers have operated perfectly. The RX-V995 worked well for a year and 2 months before it was upgraded by the RX-V2095.

    Televisions also have this. I have a JVC AV36D302 which is dead quiet. I bought a JVC AV27D302 which had a loud transformer buzz. Thinking it was defective, I returned it. I then bought a much cheaper Magnavox television(it's only for the bedroom but wish I stuck with the JVC [​IMG] ) and it's transformer buzz makes the JVC AV27302 sound quiet!! None of these electronics had a problem with their transformers so reliability may not be questionable. Getting a loud or quiet transformer seems to be hit or miss.

    Have a good one.
     
  15. Brett DiMichele

    Brett DiMichele Producer

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    Parasound has an interesting solution to transformer hum in
    the Halo line. They use a steel container around the toroid
    transformer and they pour some kind of resin between the
    transformer and the steel case (no noise what so ever..)

    Speaking of TV's...

    My RCA 61" CRT RPTV hums like a sumbitch for the first 20
    second when you turn it on.. Actually it's a high pitched
    vibration and I am fairly certain it's a charge capacitor
    that might be vibrating.. When I get the chance I will fix
    that with some hot glue.. But it's not really that bad since
    I have the TV on most of the time and you only hear it right
    when it's fired up for the first time [​IMG]
     
  16. Jonathan M

    Jonathan M Second Unit

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    Transformer hum in more expensive products is due to the fact that they use larger transformers. As Brett aluded to above, if toroid based transformers are used then hum can be further minimized. Thus, some more expensive gear that uses toroid cored transformers may hum less. Note that most equipment will hum most when first turned on - I get a nice bit of hum when my 300W DIY sub amp gets power - it has a 300VA toroid in it. Toroids are worse for this than E-I cores. My NAD T752 also has a slight hum from it's transformer - I can only just hear it though with my ear close to the thing.

    If you really want to hear some hum, just try walking past a sub station or local step-down transformer for your mains networks. You can hear them from about 20metres or more away.
     
  17. Brett DiMichele

    Brett DiMichele Producer

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    Jonathan,

    Heh substations hum big time! I work for the power company.
    I don't work with lines but I have friends that are lines
    men and also power control and they tell me about all the
    neat stuff they do [​IMG]

    Toroids do seem to hum more than E-I Cores, how come? I am
    no electronics expert so I don't know the reasoning behind
    why. My Tube amps primary and secondary transformers hum
    when powered on. They hum pretty loud when first powered
    up and then it decreases to a gentle hum that can't be
    heard unless you are real close to them. It's the nature
    of the beast I guess.
     
  18. Shiu

    Shiu Second Unit

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    Would any one be interested in google (or any other search engine) searching for "offset killer" , read about it and let me know what you think? It claims to kill mechanical (60 hz) hums that are made worse by incoming power that has an "offset" in it. Thanks
     
  19. Michael R Price

    Michael R Price Screenwriter

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    I think it might be something to do with the transformer's sensitivity to DC components and other variations in the power supply. I don't know enough about how a transformer works to discuss that, though. I read somewhere that even a few millivolts of DC on the line can make some toroids buzz. My big Plitron toroids don't buzz except on turn-on; the little one in my old amp did buzz imperceptibly. Anyone know a lot about electricity and magnetism?
     
  20. Chu Gai

    Chu Gai Lead Actor

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    Torroidal transformers have a certain susceptibility to humming as a result of this offset voltage. Their use in so many amps and receivers is due to their relatively low cost (economies of scale) and that they don't radiate much of a magnetic field. Makes life easier for the designer.
    A/C power is sinusoidal. Ideally, it crosses at the 0 Volts mark. However, there can be an offset, either positive or negative, that'll displace the sine wave up or down repectively. You still have your 120 volts though, it's just that it's displaced.
    If the offset is sufficiently large, it causes the transformer to hum, growl, because it saturates on one half of the AC cycle and not the other. A 120 to 120 isolation transformer will get rid of this offset and bring it back to zero. Maybe that's what the offset killer is but that's speculation on my part.
    I'd still take a stab at seeing how the transformer is connected as that's likely to be the easiest and cheapest approach to attenuating any hum.
     

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