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Thread: Sjostrom DC Blocker

  1. #1
    Join Date: Sep 2011

    Location: Kilmarnock, Ayrshire, Scotland

    Posts: 533
    I'm stuart.

    Default Sjostrom DC Blocker

    Recently I've stated getting hum from the transformer in my amp. It would come and go, sometimes loud, sometimes quiet and sometimes silent.

    After a bit of googling I decided to try a DC blocker and came across a rather nice bare PCB from Sjostrom Audio. They also sell a populated version but it's hardly a difficult thing to build - 4 connectors, 2 diodes and 2 caps.

    PCB duly ordered and parts purchased to let me house it in as small a plastic box as I could find (120mm x 95mm x 35mm). Took about an hour to make and it looks like it has done the trick, no more humming transformer!

    Total price was around £35.




  2. #2
    Join Date: Apr 2012

    Location: N E Kent

    Posts: 51,624
    I'm Geoff.

    Default

    That looks a handy gizmo.
    It is impossible for anything digital to sound analogue, because it isn't analogue!

  3. #3
    Bigman80 Guest

    Default

    Has it worked?

    Sent from my EVA-L09 using Tapatalk

  4. #4
    Join Date: Jan 2009

    Location: Essex

    Posts: 31,848
    I'm openingabottleofwine.

    Default



    Quote Originally Posted by Bigman80 View Post
    Has it worked?

    Sent from my EVA-L09 using Tapatalk
    Quote Originally Posted by Killie99
    Took about an hour to make and it looks like it has done the trick, no more humming transformer!
    Barry

  5. #5
    Bigman80 Guest

    Default

    Ah lol, 🤤

    Sent from my EVA-L09 using Tapatalk

  6. #6
    Join Date: Sep 2011

    Location: Kilmarnock, Ayrshire, Scotland

    Posts: 533
    I'm stuart.

    Default

    yes, it works a treat. Very simple and very effective.

  7. #7
    Join Date: Mar 2010

    Location: Sheffield

    Posts: 2,898
    I'm Simon.

    Default

    I have a pair of them, very handy.
    Kuzma Stabi/S 12", (LP12-bastard) DC motor and optical tacho psu, Benz LP, Paradise (phonostage). MB-Pro, Brooklyn dac and psu, Bruno Putzeys balanced pre, mod86p dual mono amps, Yamaha NS1000m

  8. #8
    Join Date: Apr 2011

    Location: London

    Posts: 4,419
    I'm Robert.

    Default

    Got one of these too - DC blocker or dc trap as they are known.

    'Quote' - With modern appliances all over the place doing strange things to the mains waveform (especially hair-dryers on half power and the like) you can end up with a DC component on what should be a pure AC voltage. Doesn’t even have to be in your house – could be your neighbour or somebody three doors away!

    Large toroidal transformers like the daddies in my Sansui AU-919) don’t like DC voltages, so they complain by growling or humming.......

  9. #9
    Join Date: Oct 2008

    Location: Glasgowshire

    Posts: 9,656
    I'm Gary.

    Default

    Interesting...

    Started powering my 300B SET amp from the Balanced Mains Unit and theres a bit of intermittant buzzing on the transformer?
    Its in the next room out of earshot so not annoying, but be good to eliminate it in case the DC is affecting sound quality.

    A good shout, and not too spendy, be picking one up.
    Thanks for posting Stuart.
    AC POWER
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  10. #10
    Bigman80 Guest

    Default

    Could one of these be placed at the front of a multi plug ?

    Sent from my EVA-L09 using Tapatalk

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