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Author Topic: 60hz hum using step up transfo  (Read 4043 times)

Ray Soly

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60hz hum using step up transfo
« on: November 02, 2018, 12:30:44 pm »

 Hi all,
I 'm trying to understand why, when using a 110v to 230v step up transfo and switching a speaker to 230 v (for a planned euro trip with canadian equipment) i get a 60 hz hum when i insert the signal (signal source gear is plugged into 110 direct no transfo) but, when going from the (step up) 230 to another transfo in step down 110 and reverting the selector on the speaker to 110 the same audio signal is clean ? 

For this test all the ac plugs are 110 and the speaker ac is  powercon....

Thanks

Ray
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Art Welter

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Re: 60hz hum using step up transfo
« Reply #1 on: November 02, 2018, 12:54:52 pm »

...i get a 60 hz hum when i insert the signal (signal source gear is plugged into 110 direct no transfo)
Does the speaker hum with no signal plug inserted?
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Ray Soly

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Re: 60hz hum using step up transfo
« Reply #2 on: November 02, 2018, 02:56:41 pm »

Does the speaker hum with no signal plug inserted?

no its clean

R
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John Roberts {JR}

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Re: 60hz hum using step up transfo
« Reply #3 on: November 02, 2018, 03:53:27 pm »

are any audio cables near the transformer?

JR
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Ray Soly

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Re: 60hz hum using step up transfo
« Reply #4 on: November 02, 2018, 04:40:25 pm »

are any audio cables near the transformer?

JR

no!

in both cases tested there is atb least one transfo, all ^paths for audio are the same as weel as the physical cable paths. only difference is using the one 110 to  230 vs a 110 to 230 back to a second transfo 230 to 110 ..

R

R
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Jonathan Johnson

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Re: 60hz hum using step up transfo
« Reply #5 on: November 02, 2018, 07:49:48 pm »

If the transformers are wound 2:1, you can't go from 110 to 230. You can go from 110 to 220, or 115 to 230, however. /nitpicking

Does either transformer bond a lead to the chassis of the transformer or an equipment grounding conductor (earthing conductor if not in North America)?

Does either transformer bond one of the input leads to one of the output leads (as in an autotransformer configuration)?

Is the 220 winding center tapped, and does it bond the center tap to ground or chassis?
« Last Edit: November 02, 2018, 07:52:09 pm by Jonathan Johnson »
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Ray Soly

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Re: 60hz hum using step up transfo
« Reply #6 on: November 03, 2018, 02:14:49 pm »

If the transformers are wound 2:1, you can't go from 110 to 230. You can go from 110 to 220, or 115 to 230, however. /nitpicking

Does either transformer bond a lead to the chassis of the transformer or an equipment grounding conductor (earthing conductor if not in North America)?

Does either transformer bond one of the input leads to one of the output leads (as in an autotransformer configuration)?

Is the 220 winding center tapped, and does it bond the center tap to ground or chassis?

I stand corrected on the 120 to 240 ...local french slang is "cent dix" (110) even though it,s actually 120...old habits.....

will check the leads next week ,although at this point I only needed to check the speakers did work on the selected voltage...which is either 120 or 230..

thks

Ray
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Steven A. White

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Re: 60hz hum using step up transfo
« Reply #7 on: November 29, 2018, 11:27:10 pm »

I'm interested in the step-up transformer.  Reason, I setup my home audio system rack with a 240 to 120 step down transformer.  In the end, I picked up a used "Industrial Transformer" that worked great.  Rated at 2KW.  In the evolution of the project, I picked up a "Power Converter" hoping to use that.  What the thing was is a tapped Autoformer and not a true "Isolation" type transformer.  I junked it and picked up a true isolation type transformer with 2:1 windings ratio and separate primary/secondary windings that are floating.

If what you have is an autoformer, that could be the problem.  The autoformer was in a black box, don't remember the brand.
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