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Thread: Bucking Transformer - Lower Mains Voltage by 20v

  1. #1
    Join Date: Aug 2008

    Location: Tyldesley Manchester

    Posts: 294
    I'm David.

    Default Bucking Transformer - Lower Mains Voltage by 20v

    This is useful on most vacuum tube amps from China. Most are rated 220V even though they state can be used on 240V UK. Measure your internal heater voltage and it will be typically 6.8v for regular tubes and if you are running something like 845's much higher. This shortens the life of the tube a lot and stresses the other components leading to failure.

    This was made for a 845 china made amp to drop the UK voltage 20V. It is suitable for any pre-amp and even the big 300B/ 845 power amps etc. It works different to a step down isolation transformer so don't let the size fool you. You can make your own quite easy if you have a suitable transformer. UK plug and regular iec on the end.

    Clearing out some bits...

    £15 + parcel2go postage

    Image :-

    https://drive.google.com/open?id=1r4...W6yedWwVwI9LEV
    David.

  2. #2
    Join Date: Jun 2015

    Location: London/Durham

    Posts: 6,861
    I'm Lawrence.

    Default

    PM sent!

  3. #3
    Join Date: Aug 2008

    Location: Tyldesley Manchester

    Posts: 294
    I'm David.

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    Sold I think to Lawrence.
    If you want to make one and why you should...

    http://www.dms-audio.com/bucking-transformer-diy
    David.

  4. #4
    Join Date: Jun 2015

    Location: London/Durham

    Posts: 6,861
    I'm Lawrence.

    Default

    Thought there'd be a high demand for this. I've just bought a Chinese pre so buying this in case..

  5. #5
    montesquieu Guest

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    Quote Originally Posted by Lawrence001 View Post
    Thought there'd be a high demand for this. I've just bought a Chinese pre so buying this in case..
    Yes I was beaten to the draw ... this would have been handy to have kicking around. Sadly I don't have the skills to put one together.

  6. #6
    Join Date: Jun 2015

    Location: London/Durham

    Posts: 6,861
    I'm Lawrence.

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    Ah sorry Tom, I've been after one for a while since I read some threads on here a while ago, I've had 4 Chinese valve integrateds over the years and was always worried about the strain put on them.

    Ps haven't had a chance to try the Gate pre yet, were you very keen on it?

  7. #7
    Join Date: Feb 2013

    Location: W Lothian

    Posts: 99,005
    I'm Grant.

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    Can also use a variac to do same job. It has other uses too of course Got mine on end of my Japanese market amp. It's worth more than the amp most likely
    Regards,
    Grant .... ؠ ......Don't be such a big girl's blouse

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  8. #8
    Join Date: Oct 2012

    Location: The Black Country

    Posts: 6,088
    I'm Alan.

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    Quote Originally Posted by montesquieu View Post
    Yes I was beaten to the draw ... this would have been handy to have kicking around. Sadly I don't have the skills to put one together.
    I can put one together for you Tom when you need one, at minimal charge.
    Cheers, Alan

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