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Thread: Amplifier transformer hum

  1. #1
    Join Date: Apr 2016

    Location: Bishops Stortford

    Posts: 921
    I'm Chris.

    Default Amplifier transformer hum

    In a very quiet environment and listening near field its often a little invasive hearing mechanical hum coming from the (mains) transformers, particularly in valve amps.

    My reading tells me it's probably a small amount of DC on the mains.

    I cant find any obvious culprits in the house and believe you can buy kit that you plug into the mains, then plug your gear into that.

    Any contributions?
    SW1X Universal Music Server UMS I Signature with Power Supply Unit PSU I Signature
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    SW1X Open Baffle Speakers containing both vintage and modern alnico drivers and paper cones. All silver wired and crossover-less where possible - 4" vintage Siemens Klangfilm tweeters, 8" Supravox 215 RTF64 vintage midrange drivers and vintage 15" Altec VOTT 416 bass drivers
    Hi fi Collective twin mono ladder stepped attenuator, with Charcroft Z-foil and silver wired.
    DRD 45 single ended, 45 triode, monoblocks,
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  2. #2
    Join Date: Dec 2017

    Location: Lincolnshire

    Posts: 309
    I'm Martin.

    Default

    If it is DC you have an issue with then have a look here:

    https://sjostromaudio.net/cart/gb/ and here:

    https://www.atlhifi.com/

  3. #3
    Join Date: Mar 2008

    Location: Galashiels

    Posts: 13,111
    I'm inthescottishmafia.

    Default

    If you are handy with a soldering iron, a DC blocking IEC socket can be fitted to the amp. Failing that you can buy a filter like this-

    https://www.mcru.co.uk/product/mcru-in-line-dc-blocker/
    “Music has always been a matter of energy to me, a question of fuel. Sentimental people call it inspiration, but what they really mean is fuel. I have always needed fuel. I am a serious consumer. On some nights I still believe that a car with the gas needle on empty can run about fifty more miles if you have the right music very loud on the radio”

    Hunter S Thompson

  4. #4
    Join Date: Apr 2016

    Location: Bishops Stortford

    Posts: 921
    I'm Chris.

    Default

    https://sjostromaudio.net/cart/gb/

    DCT02 DC FILTER FOR TOROIDAL TRANSFORMERS, BUILT UNIT

    Does this mean that this unit works best with toroidal transformers or that toroidals are notoriously more noisy?
    SW1X Universal Music Server UMS I Signature with Power Supply Unit PSU I Signature
    SW1X USB II
    SW1X DAC III Special
    SW1X Open Baffle Speakers containing both vintage and modern alnico drivers and paper cones. All silver wired and crossover-less where possible - 4" vintage Siemens Klangfilm tweeters, 8" Supravox 215 RTF64 vintage midrange drivers and vintage 15" Altec VOTT 416 bass drivers
    Hi fi Collective twin mono ladder stepped attenuator, with Charcroft Z-foil and silver wired.
    DRD 45 single ended, 45 triode, monoblocks,
    Silver mains cables, interconnects and speaker cables by SW1X

  5. #5
    Join Date: Apr 2016

    Location: Bishops Stortford

    Posts: 921
    I'm Chris.

    Default

    Quote Originally Posted by Ali Tait View Post
    If you are handy with a soldering iron, a DC blocking IEC socket can be fitted to the amp. Failing that you can buy a filter like this-

    https://www.mcru.co.uk/product/mcru-in-line-dc-blocker/
    Am happy to wield a soldering iron, and a pre-built PCB looks good. This is very much to prove this is the source of the hum, so will invest in a better bit of kit later if it works
    SW1X Universal Music Server UMS I Signature with Power Supply Unit PSU I Signature
    SW1X USB II
    SW1X DAC III Special
    SW1X Open Baffle Speakers containing both vintage and modern alnico drivers and paper cones. All silver wired and crossover-less where possible - 4" vintage Siemens Klangfilm tweeters, 8" Supravox 215 RTF64 vintage midrange drivers and vintage 15" Altec VOTT 416 bass drivers
    Hi fi Collective twin mono ladder stepped attenuator, with Charcroft Z-foil and silver wired.
    DRD 45 single ended, 45 triode, monoblocks,
    Silver mains cables, interconnects and speaker cables by SW1X

  6. #6
    Join Date: Mar 2008

    Location: Galashiels

    Posts: 13,111
    I'm inthescottishmafia.

    Default

    Quote Originally Posted by bumpy View Post
    https://sjostromaudio.net/cart/gb/

    DCT02 DC FILTER FOR TOROIDAL TRANSFORMERS, BUILT UNIT

    Does this mean that this unit works best with toroidal transformers or that toroidals are notoriously more noisy?
    Toroids are less tolerant of DC than IE types.
    “Music has always been a matter of energy to me, a question of fuel. Sentimental people call it inspiration, but what they really mean is fuel. I have always needed fuel. I am a serious consumer. On some nights I still believe that a car with the gas needle on empty can run about fifty more miles if you have the right music very loud on the radio”

    Hunter S Thompson

  7. #7
    Join Date: Jan 2018

    Location: blackpool

    Posts: 217
    I'm neil.

    Default

    I have a similar problem - but maybe more severe,the mains seems to be very noisy particularly when the boiler is on, I can't use the Phono when it is on !!
    I have a valve amp and Phono-I have found SS phonos are also affected but not to the extent of the valve one
    I am trying to get my engineer to look at the phono to make sure its ok - just wondering if the DC blockers would help in the meantime
    Would this do https://www.atlhifi.com/shop/fully-a...-2-ac-outlets/
    Would I be able to plug in the Amp and Phono?
    Cheers
    Sorry to gatecrash the thread

  8. #8
    Join Date: Dec 2017

    Location: Lincolnshire

    Posts: 309
    I'm Martin.

    Default

    Just need to make sure it's DC that's your issue otherwise it probably won't do all that you need.

  9. #9
    Join Date: Oct 2016

    Location: London

    Posts: 223
    I'm David.

    Default

    Quote Originally Posted by bumpy View Post
    In a very quiet environment and listening near field its often a little invasive hearing mechanical hum coming from the (mains) transformers, particularly in valve amps.

    My reading tells me it's probably a small amount of DC on the mains.

    I cant find any obvious culprits in the house and believe you can buy kit that you plug into the mains, then plug your gear into that.

    Any contributions?
    Hi,
    I think it's a little more complex than the above replies imply. Many valve IE transformers hum, just ask any Radford STA 25 owner! In some cases this may be because of DC on the mains but IME it's down to transformer design /build. EG my Leben CS 1000p with Hashimoto transformers does not hum at all whereas the Radford transformers I've used in a Radford STA 100 monoblock build hum like a New Orleans gospel choir, as do the Edcor EI transformers I used in the past in my pre builds and Cannonball power amps. A couple of things I've learned are:

    1. DC blockers have no effect on the hum in these transformers and I have heard they kill the sound on valve amps but havn't expereinced that myself. But for the cost it's worth a try.

    2. Toroidal Transformers
    Again, whether they hum or not seems to be down to transformer design. Decent ones don't hum whilst some cheaper ones do and DC blockers don't tend to help these either. But DC blockers do seem to work well on large solid state amps with big toroidal transformers without any impact on SQ.

    @enrae8 You say the 'mains is noisy' but are you referring to transformer buzz or something else?

    David

  10. #10
    Join Date: Jan 2018

    Location: blackpool

    Posts: 217
    I'm neil.

    Unhappy

    Quote Originally Posted by AD Audio View Post
    Hi,

    @enrae8 You say the 'mains is noisy' but are you referring to transformer buzz or something else?

    David
    Hi - I have a bit of transformer hum - but I can live with that
    The mains problem - loud pops, I guess when switches relays are activating in the boiler also loud buzzes maybe from the pump, pops also occur when other things are used, electric carving knife, blender etc..I've tried extension lead from upstairs etc..The Kitchen diner has its own board as it was refurbed a couple of years ago - the boiler is ancient, we should be getting a new one and having it on its own feed should have happened last year

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