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Thread: Power amp transformer hum

  1. #21
    Join Date: Jan 2008

    Location: Gerrards Cross

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    I'm Tony.

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    I would suggest finding the null point of the transformer first that's always a good place to start, every TX has one you, you just have to find it.
    Coherent Systems
    Real high end sound with musicality not hifi

  2. #22
    Join Date: Apr 2012

    Location: London

    Posts: 353
    I'm james.

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    Not necessarily poor quality, these things can develop with time in EI cores at least. Another problem is manufacturers using 'tightly spec'd' transformers which work harder and more efficiently but are more prone to hum. I've had this with MF kit, annoying it is too.

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  3. #23
    Join Date: May 2018

    Location: London

    Posts: 12
    I'm Tommy.

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    Hi there. There are ways to measure the electricity in the wall socket for how much dc you have. Then there is a formula to calculate how you need too build the dc blocker. I did read a lot about the problem in Norwegian forums. But as mentioned before, this is way over my head.
    So for people that just buy a accidentally dc blocker it might be to small and not remove enough dc.

    But you are also right about the audiphile trafos. But maybe people here reacts to word as "audiophile" or "high end" trafoes .

    The truth is that it is difficult to make perfect trafoes. But when the quality is good the trafo will not "hum"
    So if you change to quality trafos, the hum will be gone.
    Of course the dc is still in your electricity net. So some high end people still believe that the best is to have dc blocker even if it is quiet.
    Quote Originally Posted by Bigman80 View Post
    Cheers Tommy, the design of the PCB is one I bought online. There may be capped for more blockage.

    How can I test what it's blocking?
    Tommy

  4. #24
    Join Date: Apr 2018

    Location: Brighton

    Posts: 6
    I'm Jason.

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    As AnthonyTD said, if the buzzing was caused by DC offset, I would expect the buzzing to vary during the day.

  5. #25
    Join Date: May 2018

    Location: London

    Posts: 12
    I'm Tommy.

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    Quote Originally Posted by blackmetalboon View Post
    As AnthonyTD said, if the buzzing was caused by DC offset, I would expect the buzzing to vary during the day.
    Yes, this is correct.


    Tommy

  6. #26
    Join Date: Jan 2009

    Location: Essex

    Posts: 17,885
    I'm openingabottleofwine.

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    If the transformer noise is due to DC offset on the mains, the 'hum' will be at 50Hz. If due to loose laminations, the 'hum' will be at 100Hz.
    Last edited by Barry; 04-07-2018 at 16:49.
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  7. #27
    Join Date: Jul 2012

    Location: Benson, Oxfordshire

    Posts: 490
    I'm Alex.

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    So, these are my transformers:

    I have no idea how they rank quality wise...?


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  8. #28
    Join Date: Nov 2015

    Location: Wolverhampton

    Posts: 5,692
    I'm Oliver.

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    I have a Noratel too. Mine is potted. Doesn't hum.

    Like I said, in audio application, you really need silence from it.

    When I first built the DIY phonostage, I could hear the vibration of the TF through the speakers. It was really bad. It was my experience that having a noisy TF like that definitely affected the sound quality.

    Spending the money on the Toriody was worth every penny IMO. Obviously, there are others with other opinions but my mind is set on only buying high quality TFs from now on.
    Quote Originally Posted by alcarmichael View Post
    So, these are my transformers:

    I have no idea how they rank quality wise...?


    Sent from my iPhone using Tapatalk
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  9. #29
    Join Date: Feb 2008

    Location: South Wales

    Posts: 6,689
    I'm NotTakingLifeTooSeriouslyTheseDays.

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    Hi Alex,
    Another aspect I have found affects Transformer noise to a lesser, or greater degree, is the over voltage aspect, most European designed transformers are wound for 230v these days...Here in the UK, the voltage can vary between 237v to just under 260v in some areas [yes I have confirmation of this] So, this in itself, will have a very noticeable affect on the transformer in some aplications, not to mention the higher secondary voltages, and their affect on the components, and circuitry design!
    A...
    Quote Originally Posted by alcarmichael View Post
    So, these are my transformers:

    I have no idea how they rank quality wise...?


    Sent from my iPhone using Tapatalk
    "Today scientists have substituted mathematics for experiments, and they wander off through equation after equation, and eventually build a structure which has no relation to reality"
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  10. #30
    Join Date: Oct 2016

    Location: Bolton, England

    Posts: 1,248
    I'm Andrew.

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    Quote Originally Posted by Bigman80 View Post
    When I first built the DIY phonostage, I could hear the vibration of the TF through the speakers. It was really bad.
    Interesting. How did mechanical buzz manage to create an electrical signal in the speakers?

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