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Tweakers' Asylum Tweaks for systems, rooms and Do It Yourself (DIY) help. FAQ. |
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Tweakers' Asylum Tweaks for systems, rooms and Do It Yourself (DIY) help. FAQ. |
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In Reply to: RE: Has anyone made an audiophile grade cheater plug? posted by Awe-d-o-file on July 1, 2007 at 08:42:17:
I've got the scars to show what that causes.
The third wire (AC safety-earth, aka "ground") in the present USA domestic wiring scheme is there to keep a faulty appliance from killing someone. Appliance manufacturers have the choice of making their products with two or three power wires. A two-wire appliance is "double-insulated," which means there is adequate internal insulation to keep any conceivable internal fault from bringing the user into contact with the hot wire. A double-insulated appliance such as a hair dryer can still be lethal if dropped into a bathtub, which is why we also have ground-fault interrupters on AC outlets near plumbing fixtures required by code.
Unfortunately for audiophiles, most fancy gear is made with three-wire power cords. The ground loop is the circuit connecting amplifier audio ground to source audio ground through both the interconnect cable ground as well as the AC safety-earth wiring. Hum results if there is any voltage generated within the safety-earth wiring, as it appears in series with the audio signal as far as the amplifier is concerned. Lifting the AC safety-earth connection with a cheater plug breaks that side of the audio ground loop, and cures the hum problem. However, it removes the safety aspect of the equipment design.
How dangerous is this? It is difficult for users to evaluate their risk in defeating a safety measure that only functions rarely. How likely is a party guest or child to spill liquid into your equipment? How likely is your equipment to contain a design blunder, that causes equipment to fail after a long period of use? I've owned four solid-state amps in my life, and one had such a blunder, so my guess is 25%. What is yours?
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- In the bad old days, cars did not have seatbelts, either. - Al Sekela 14:18:45 07/01/07 (0)
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