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    Mechanical hum: power transformer

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    2turbos

    Posts : 6
    Join date : 2009-09-20

    Mechanical hum: power transformer

    Post by 2turbos on Wed Oct 18, 2017 4:55 pm

    I have a hum problem with my Stereo 70. It's mechanical, no detectable  hum in the signal on the outputs.

    I assume it has to do with the way the transformer mounts to the chassis. If I put a heavy weight on it then the buzz stops.

    Any way to isolate the transformer mechanically?


    Last edited by 2turbos on Wed Oct 18, 2017 4:56 pm; edited 1 time in total (Reason for editing : grammar)
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    Bob Latino
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    Posts : 2579
    Join date : 2008-11-26
    Location : Massachusetts

    Re: Mechanical hum: power transformer

    Post by Bob Latino on Wed Oct 18, 2017 7:51 pm

    2turbos wrote:I have a hum problem with my Stereo 70. It's mechanical, no detectable  hum in the signal on the outputs.

    I assume it has to do with the way the transformer mounts to the chassis. If I put a heavy weight on it then the buzz stops.

    Any way to isolate the transformer mechanically?

    Get FOUR 00 (double zero) flat neoprene plumbing washers and place them between the transformer and the top of the chassis. These will absorb most of the mechanical vibrations of the power transformer. Don't overtighten on top of these washers or you will flatten them out and they will loose their ability to absorb the vibrations.

    All VTA amps have "isolation washers" between the power transformers and the chassis.

    Bob

    2turbos

    Posts : 6
    Join date : 2009-09-20

    Re: Mechanical hum: power transformer

    Post by 2turbos on Wed Oct 18, 2017 8:07 pm

    Bob Latino wrote:
    2turbos wrote:I have a hum problem with my Stereo 70. It's mechanical, no detectable  hum in the signal on the outputs.

    I assume it has to do with the way the transformer mounts to the chassis. If I put a heavy weight on it then the buzz stops.

    Any way to isolate the transformer mechanically?

    Get FOUR 00 (double zero) flat neoprene plumbing washers and place them between the transformer and the top of the chassis. These will absorb most of the mechanical vibrations of the power transformer. Don't overtighten on top of these washers or you will flatten them out and they will loose their ability to absorb the vibrations.

    All VTA amps have "isolation washers" between the power transformers and the chassis.

    Bob

    Thanks Bob. I was thinking along those same lines but wanted to check with forum members to see what they had done.
    Sounds like this problem already has a solution.
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    PeterCapo

    Posts : 455
    Join date : 2008-12-05

    Re: Mechanical hum: power transformer

    Post by PeterCapo on Thu Oct 19, 2017 9:39 pm

    Dynakitparts offers an isolation kit for the power transformer to reduce vibration http://www.dynakitparts.com/dynakit-products/hardware/POWER-TRANSFORMER-ISOLATION-MOUNTS

    There might also be some DC offset on the AC mains, and I have read posts by others who, having eliminated the DC component, had a more peaceful power transformer:

    https://emotiva.com/product/cmx-2/

    and

    http://avahifi.com/products/accessories/humdinger-dc-line-blocker

    You might also try snugging the bolts holding the transformer cover on.

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