Center tap transformer grounded through caps - diyAudio
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Old 9th November 2013, 11:34 AM   #1
Niquel is offline Niquel  Spain
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Join Date: Feb 2012
Default Center tap transformer grounded through caps


I have a Mosfet guitar amplifier which power supply is shown in the following schematic. The power supply for the power amp section is +50V 0 -50V and feeds the preamp power supply through 470Ohm 5W and 1K 5W resistors. But I don't understand the purpose for the 0,1uF caps between the 0V line and earth instead of linking it direct to the chassis as other amp builders.

Thanks in advance.
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Old 10th November 2013, 01:49 PM   #2
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This ist done due to ground the amplifier's ground bus RF-wise, but all for that to avoid ground loops if another grounded device will be connected to it.

Best regards!
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Old 11th November 2013, 06:01 PM   #3
Niquel is offline Niquel  Spain
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Join Date: Feb 2012
Thank you kay Pirinha for your help!
I found this web site where everything is clearly explained
I suspected it had something to do with noise but I still don't understand if it is a safe way, as it cuts the path to ground.
Thanks once more.
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Old 11th November 2013, 06:41 PM   #4
jcx is offline jcx  United States
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floating/isolated mains device safety depends on the component's rating, proper construction

the transformer needs to be built to "double or reinforced insulation" standards for the mains V and pass a 4kV Hipot test

all line side wiring, parts must be secured so that they can't short to the chassis with any "single fault"

legal commercial equipment should have safety standards labels including wording or symbol for floating output
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Old 12th November 2013, 02:40 PM   #5
Niquel is offline Niquel  Spain
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Join Date: Feb 2012
Thanks jcx,
It is a little bit more clear.
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