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Thread: Power amp transformer hum

  1. #11
    Join Date: Nov 2015

    Location: Wolverhampton

    Posts: 5,699
    I'm Oliver.

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    A DC blocker is unlikely to eradicate the problem. I use one and they still buzz, although it does reduce it *very little*

    I have transformers which have Mechanical buzz, which is what you have.

    The ONLY way to entirely rectify it, is to replace the TFs with audiophile quality ones. Airlink and Toriody (I like Toriody) have audiophile quality TFs but drop them an email and specify that's what they are for.

    I've used multiple cheaper Chinese alternatives and ended up throwing them out due to the noise they make

    They buzz because the laminations arent glued together 100%. Whilst this has no bearing on functionality, it does make them noisy.

    This one is in my valve phonostage, after chucking the noisy Chinese bought one. Worth every penny.
    Analogue: Technics SP10 MK2 > Phonomac AT-1010 MK5 tonearm > Ortofon Kontrapunkt b > Wizard Jfet MC Valve Phonostage (Telefunken Valves)
    Digital: Firebottle modded Xiang Sheng DAC (Telefunken Valve)
    Amplification: Nelson Pass DCB1 & Firebottle Monoblocks (Telefunken Valves) & Monarchy Audio SM-70 Class A Amplifier
    Cables: Fisual S-Flex Speaker Cable & SPOTFIRE IC Cables & NEW SPOTFIRE Tonearm cable
    Speakers: Pioneer CS-77A

  2. #12
    Join Date: May 2018

    Location: London

    Posts: 12
    I'm Tommy.

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    You could be right about this.
    But maybe your dc blocker was not removing enough dc volts?
    Some only removes 0.5 volts. Others removes up to several volts.
    If you have dc 2 volts and use a dc blocker that removes 1 volt you will notice a difference. But the hum only gets lower .
    This is possible to measure and build a blocker that is strong enough.
    I'm not shore about hove much the one I linked to removes. But I think I did read somewhere it is in the range of somewhere between 2 and 4 volts.
    It's easy to calculate if you have the skills, I don't.

    In my case in an acoustic treated (quiet)room I could hear the hum from 4 meters. Of course the noise was depending on howe mutch dc it was at the moment. But worst case cenario 4 meters.
    With the dc blocker it's always quiet. Or the truth, if I put my ear dawn on the top of amplifier and the room is totally quiet I might sometimes hear it. But that is good enough.
    Quote Originally Posted by Bigman80 View Post
    A DC blocker is unlikely to eradicate the problem. I use one and they still buzz, although it does reduce it *very little*

    I have transformers which have Mechanical buzz, which is what you have.

    The ONLY way to entirely rectify it, is to replace the TFs with audiophile quality ones. Airlink and Toriody (I like Toriody) have audiophile quality TFs but drop them an email and specify that's what they are for.

    I've used multiple cheaper Chinese alternatives and ended up throwing them out due to the noise they make

    They buzz because the laminations arent glued together 100%. Whilst this has no bearing on functionality, it does make them noisy.

    This one is in my valve phonostage, after chucking the noisy Chinese bought one. Worth every penny.
    Tommy

  3. #13
    Join Date: May 2018

    Location: London

    Posts: 12
    I'm Tommy.

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    Forgot to tell that my amplifier is fully balanced and have 4 toroidal trafos. 4 times 500va.
    And I suspected first bad quality trafos since they are 20 years old. And in that case the dc blocker as mentioned above will not help.
    But all 4 is quiet now.

    Tommy

  4. #14
    Join Date: Feb 2008

    Location: Down South

    Posts: 2,236
    I'm Neal.

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    ^^^ Exactly. Also Torodial transformers donít have Ďlaminationsí as such, the core generally being wound from a single continuous strip of nickel iron or moulded to shape from a ferrite material.
    Listening in a Foo free Zone...

    Only a Sith deals in absolutes.

  5. #15
    Join Date: Oct 2016

    Location: Bolton, England

    Posts: 1,249
    I'm Andrew.

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    Quote Originally Posted by Bigman80 View Post
    I have transformers which have Mechanical buzz, which is what you have.
    The ONLY way to entirely rectify it, is to replace the TFs with audiophile quality ones. Airlink and Toriody (I like Toriody) have audiophile quality TFs but drop them an email and specify that's what they are for.
    I think you're over-stating the problem a bit, there. E-I transformers can rattle/buzz very badly, but the problem isn't that hard to cure and you don't need "audiophile" transformers. The bolts that hold the laminations together can be be tightened (or even loosened in some cases) which can have a beneficial effect. Also, potting the transformer in varnish should eliminate rattles and buzzes. That's something which can be done at home with ordinary oil-based varnish.
    However, toroids are constructed differently so the same methods as used for E-I transformers don't apply.

    Bear in mind that the problem might not be the transformer itself anyway. I've known steel enclosures to rattle due to induction from the transformer. The cure is to move the transformer within the enclosure (if that's even possible) or to tighten or loosen fixing bolts or somehow damp the movement of the enclosure.

  6. #16
    Join Date: Feb 2008

    Location: South Wales

    Posts: 6,689
    I'm NotTakingLifeTooSeriouslyTheseDays.

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    Just to add to the below comment from Andrew, try to establish if the noise gets worse at paticular times of day/night, and if the frequency changes slightly.
    Quote Originally Posted by RothwellAudio View Post

    Bear in mind that the problem might not be the transformer itself anyway. I've known steel enclosures to rattle due to induction from the transformer. The cure is to move the transformer within the enclosure (if that's even possible) or to tighten or loosen fixing bolts or somehow damp the movement of the enclosure.
    "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"
    Nikola Tesla



    We Send our kids to school to be Educated, not Medicated!

  7. #17
    Join Date: Nov 2015

    Location: Wolverhampton

    Posts: 5,699
    I'm Oliver.

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    Quote Originally Posted by RothwellAudio View Post
    I think you're over-stating the problem a bit, there. E-I transformers can rattle/buzz very badly, but the problem isn't that hard to cure and you don't need "audiophile" transformers. The bolts that hold the laminations together can be be tightened (or even loosened in some cases) which can have a beneficial effect. Also, potting the transformer in varnish should eliminate rattles and buzzes. That's something which can be done at home with ordinary oil-based varnish.
    However, toroids are constructed differently so the same methods as used for E-I transformers don't apply.

    Bear in mind that the problem might not be the transformer itself anyway. I've known steel enclosures to rattle due to induction from the transformer. The cure is to move the transformer within the enclosure (if that's even possible) or to tighten or loosen fixing bolts or somehow damp the movement of the enclosure.
    I don't think I am, I bought a Airlink TF for my BMU, it buzzed like a bee in an echo chamber. I sent it back after trying to bolt it tighter, adding rubber washers under it, doubling the isolation etc and in the end, the only way to rid myself of the buzzing was to specify it had to be silent. I've been in this situation on 3/4 occasions and this solution is the best remedy.

    TFs dipped in varnish have remained noisy IME
    Analogue: Technics SP10 MK2 > Phonomac AT-1010 MK5 tonearm > Ortofon Kontrapunkt b > Wizard Jfet MC Valve Phonostage (Telefunken Valves)
    Digital: Firebottle modded Xiang Sheng DAC (Telefunken Valve)
    Amplification: Nelson Pass DCB1 & Firebottle Monoblocks (Telefunken Valves) & Monarchy Audio SM-70 Class A Amplifier
    Cables: Fisual S-Flex Speaker Cable & SPOTFIRE IC Cables & NEW SPOTFIRE Tonearm cable
    Speakers: Pioneer CS-77A

  8. #18
    Join Date: Nov 2015

    Location: Wolverhampton

    Posts: 5,699
    I'm Oliver.

    Default

    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?
    Quote Originally Posted by 2fastgt4 View Post
    You could be right about this.
    But maybe your dc blocker was not removing enough dc volts?
    Some only removes 0.5 volts. Others removes up to several volts.
    If you have dc 2 volts and use a dc blocker that removes 1 volt you will notice a difference. But the hum only gets lower .
    This is possible to measure and build a blocker that is strong enough.
    I'm not shore about hove much the one I linked to removes. But I think I did read somewhere it is in the range of somewhere between 2 and 4 volts.
    It's easy to calculate if you have the skills, I don't.

    In my case in an acoustic treated (quiet)room I could hear the hum from 4 meters. Of course the noise was depending on howe mutch dc it was at the moment. But worst case cenario 4 meters.
    With the dc blocker it's always quiet. Or the truth, if I put my ear dawn on the top of amplifier and the room is totally quiet I might sometimes hear it. But that is good enough.

    Tommy
    Analogue: Technics SP10 MK2 > Phonomac AT-1010 MK5 tonearm > Ortofon Kontrapunkt b > Wizard Jfet MC Valve Phonostage (Telefunken Valves)
    Digital: Firebottle modded Xiang Sheng DAC (Telefunken Valve)
    Amplification: Nelson Pass DCB1 & Firebottle Monoblocks (Telefunken Valves) & Monarchy Audio SM-70 Class A Amplifier
    Cables: Fisual S-Flex Speaker Cable & SPOTFIRE IC Cables & NEW SPOTFIRE Tonearm cable
    Speakers: Pioneer CS-77A

  9. #19
    Join Date: Jul 2012

    Location: Benson, Oxfordshire

    Posts: 490
    I'm Alex.

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    With regard to a poor quality transformer being the potential cause, surely a company as highly regarded as Avondale would use good quality transformers?

  10. #20
    Join Date: May 2016

    Location: Notts

    Posts: 1,422
    I'm Geoff.

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    Quote Originally Posted by bumpy View Post
    If the hum is mechanical and if you feel,comfortable, this is what I would do.

    Put the amp on till it hums then remove the top to see if this in itself has had an effect. Then bare down on various parts of the chassis and transformer with a wooden stick. You may well find that tightening down or a new rubber washer will sort things out.

    Good luck
    Unless you have a fully paid up funeral plan I would not start poking around a powered up valve amp with a wooden stick or anything else for that matter! For your education I am attaching a picture of a rat that tried to chew one of my "live" hifi power cables in Malawi!

    Rat Explosion.jpg

    Pay careful attention to the emission trail to the right of the photo!

    Geoff

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