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Earth to laptop PSU when used for audio

PATGuard 3 Forum

Earth to laptop PSU when used for audio

Postby Alan Freeman » Sat Aug 26, 2017 12:16 pm

I am in two minds. My laptop has a class 1 PSU with earth continuity from the IEC earth pin to the outer of the DC plug and on the the screen of the headphone socket. Passes fine..... but....

There is a known problem with earthing of audio equipment which generates a 50Hz hum if an earthed source is connected to an earthed mixer or amplifier.

Most audio sources (CD/tape/tuners etc) are class 2 or have isolated signal earths. The earth comes down the audio lead from the mixer or amplifier.

My laptop is class 1 to the audio connector and causes a hum.

What is the thought about lifting the earth connection to the PSU effectively calling it class 2?? Very NON PAT - but the only way I can see of removing the hum loop.
Alan Freeman
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Re: Earth to laptop PSU when used for audio

Postby Grizzly » Wed Aug 30, 2017 11:53 am

Nah, don't do that Alan.
You wouldn't be 'effectively calling at a Class II'. You'd be removing the functional earth from the PSU, with who knows what results.

Better to get some sort of hum loop eliminator. Here's a cheap one from CPC:

Many others are available.
C&G 2377 -01 & -02
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