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jaycee · 08-01-2007, 01:23

The noise you are hearing comes from the power supply. Some cheaply made transformers used in high frequency switched mode supplies are not impregnated with polyurethane, so what you hear is the windings of the transformer vibrating at whatever the power supplies frequency is (probably 20KHz)

08-01-2007, 01:23	#6
jaycee Inactive Join Date: May 2005 Posts: 304	Re: high pitch noise The noise you are hearing comes from the power supply. Some cheaply made transformers used in high frequency switched mode supplies are not impregnated with polyurethane, so what you hear is the windings of the transformer vibrating at whatever the power supplies frequency is (probably 20KHz)