audio interference from earth ground (update) - Page 1
Forum section: electronics / general

author: Tidwell420
author_rank: Contributor
timestamp: April 04, 2013, 08:25:31 pm
content: i have yet to try any of the solutions suggested to remove noise from the computers audio connection to my stereo but i have been doing some work to the house here and found something a little interesting. seems the last time the wiring on the house was done which was about 50+ years ago for most of it i found a short going from neutral to ground and after swapping the outlet with a new one and not shorting neutral to ground like it was done on the old outlet. the buzz i used to hear on the audio seems to be less noticeable. i'm thinking that there may still be a neutral to ground short elsewhere in the house. from what i was reading on several websites this neutral to ground short is not up to code and could possibly cause someone to an electric shock. i was also doing other work in the same room and it seem something went wrong with my ceiling fan as after i finished painting i was putting the fan back together and decided to test it and i heard a zap and a saw some sparks fly i quick switched it off but what scared me more was the fact the circuit breaker for the fan never tripped i do not know why. i am beginning to think a total house rewiring is needed. i am also wondering if neutral to ground was ever a good idea or was it something someone did just to save some time. any thoughts or ideas would help. thank you

author: madires
author_rank: Super Contributor
timestamp: April 04, 2013, 09:04:25 pm
content: The audio problem is caused by a so called "ground loop". The ground of your PC is connected to the chassis and the earth pin of the power cable. If your stereo also has a connection to earth you'll get a nice hum :-) The common solution is to use an audio transformer (1:1). And regarding your power wiring you should consult a licensed electrician who knows your local safety and installation requirements. In most cases you got earth and neutral connected in (front of) the main distribution.

author: lemmegraphdat
author_rank: Frequent Contributor
timestamp: April 05, 2013, 02:10:00 am
content: The neutral wire is carrying full circuit current. What this means is that if the neutral wire, which is actually a hot wire, is connected to the safety ground and you get between the safety ground and lets say a water pipe, you are gonna get creamed. The safety ground is now a live conductor.

author: Monkeh
author_rank: Super Contributor
timestamp: April 05, 2013, 02:10:06 pm
content: Quote from: lemmegraphdat on April 05, 2013, 02:10:00 amNot generally, no, you're not going to get 'creamed'..

author: ddavidebor
author_rank: Super Contributor
timestamp: April 05, 2013, 02:15:37 pm
content: and also no if the safety earth work fine.

author: Unknown
author_rank: Unknown
timestamp: April 05, 2013, 02:36:32 pm
content: QuoteAlso, any audio system that has separate units, and individual Earth Tags/Terminals for each unit, only one Earth is required to the mains supply.The rest of the system picks up there Earth's via the interconnected audio fly leads; so if you have made two mains Earth connections from individual units, then an Earth-Loop has been created, and only one needs to be removed.The transformer 1:1 ratio is valid, in situations where voltage differences exist between equipments, and can be just 20 mV or less to induce mains HUM on median gain input stages... if a PC is used along with your Hi-Fi system, then a 1:1 transformer is recommended, between the audio in and output feeds.

author: jpb
author_rank: Super Contributor
timestamp: April 05, 2013, 02:43:07 pm
content: The neutral is normally connected to earth at the point where the power enters the house (the consumer unit) I believe. If it is connected elsewhere there is a danger that the earth wiring will start carrying some of the return current which would cause any residual current devices to trip as well as meaning earth potential could rise above true earth which is not a good thing but is unlikely to be as lethal as the live wire.I recently bought a Fluke SM300 to test some sockets I'd added to my workbench. One thing that does is test for raised earth voltage as well as generally checking no earth leakage and that RCDs are working. If you're worried about your wiring it may be worth getting one and doing a few checks.

author: lemmegraphdat
author_rank: Frequent Contributor
timestamp: April 06, 2013, 12:29:17 am
content: Quote from: jpb on April 05, 2013, 02:43:07 pmWell I'm a little cautious. I flipped on a 100 amp 3 ph breaker once and the whole plant went down. The whole freakin' plant. The outlet that the other guy wired shorted 3 phases to the box. What a freak out.

author: Tidwell420
author_rank: Contributor
timestamp: April 06, 2013, 06:18:26 pm
content: who was the idiot that thought cloth was a good way to insulate wires?installed a new ceiling fan yesterday and found the reason i saw sparks it was some cloth covered wire that had some bare spots that were grounding out. I'm glad i found this problem cause if I hadn't I'm sure it may as well caught fire

author: Tidwell420
author_rank: Contributor
timestamp: April 06, 2013, 06:33:48 pm
content: Quote from: jpb on April 05, 2013, 02:43:07 pmafter some research it is electric code here to normally connect neutral to earth at the point where the power enters the house and yes there could have been potential for someone to get shocked but seeing how it was done about 60 years ago its surprising no one has

author: kaindub
author_rank: Regular Contributor
timestamp: April 07, 2013, 10:23:46 am
content: If your house has cloth insulated wiring, I'd say the wiring is more than 50 years oldPVC insulated wiring has been in use for some 60 or 70 years.I'd say your house probably needs a rewire - to get rid of old style wiring and to bring it uo to code

author: Tidwell420
author_rank: Contributor
timestamp: April 10, 2013, 03:44:40 am
content: Quote from: kaindub on April 07, 2013, 10:23:46 ami'd love to see this house rewired but sadly i think its out of this household's budget at least for now

author: ddavidebor
author_rank: Super Contributor
timestamp: April 10, 2013, 05:07:32 am
content: Well, a safety check from a PROFESSIONAL (aka a real one, with his name on the car and funky expensive test equipment) electrician should be a good idea.