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Old 1st December 2010, 03:24 AM   #1
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Default Stop feedback from capacitors into power...

First I have poor wiring in my apartment...

I have a problem with AC filter capacitors feeding back into my system, or the other power around.

I had to get rid of the neutral to ground filter all together because the ground was so poor that it would feed back into the neutral and give extensive noise in all of the system. It sucked. I think it was a case of looking for least resistance or something because in the past it has been the best digital filtering I have achieved.

The mains however... anything not on the AC filter (ever seen a Audience Adept, that is essentially what I made without teflon capacitors) gets noise... way too much.

I am starting to wonder if there is a way to flatten what is filtered out. Know what I mean? I am thinking of the attenuated signal by the capacitors being turned into DC, bled off through a resistor/light-bulb, something... hell I even thought about wiring a battery in that provided the current but one I am unsure how long it would last. (mains positive and battery positive connected with large resistor, and negative of battery connected to negative of capacitors, with positive of capacitor connected to mains positive) Sounds plausable huh? Two however is that I have never seen 115v batteries.

Unfortunately I am not coming up with any decent solutions, so I was thinking maybe someone on here would have an idea. Basically it does not matter how the frequency of voltage changes in the attenuated range so long as it is not re-entering the house circuit. If I solve this I can get the better digital filtering with the neutral to earth ground.
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Old 1st December 2010, 03:38 AM   #2
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If your apartment building is very old you may not have a ground(earth) connection(green or bare wire). My buddy sold his old house last year and he had to pay for an electrician to rewire his house. It had the old knob and tube wiring all through the house. ie 2 bare wires in the wall seperated by ceramic knobs and tubes where the wires passed thru walls. All of his electrical outles were 2 prong not 3. Take the cover off of an outlet and look inside you should see 3 wires a bare copper(earth) black ( hot) and neutral( white). Measure between all three. 110 between black and white, 110 between black and bare, zero or almost zero between white and bare.
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Old 1st December 2010, 03:44 AM   #3
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Way ahead of you buddy. Earth ground is the grounding of the conduit due to "updates" in the basement to allow a modern heating unit to regulate the steam system.

It is not proper earth ground and you are not posting any sort of relation to my question. As I said before I had to remove the neutral to earth ground filter because the earth ground is so poor that I got nothing but huge noise being fed back into the system.

Now I am wondering if I connected it back up but put a resistor inline with the neutral pre-filter, if it would then dump the noise into the conduit "earth ground". The challenge is that the resistor would have to be less than any given piece of equipments resistance and I am not sure if the value would be high enough.
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Old 1st December 2010, 11:17 AM   #4
AndrewT is offline AndrewT  Scotland
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I think the current UK regulations do not allow the conduit to act as the Earth.
There must be a direct wire link all the way back to the Earth on the distribution board. This PE link must be tested to prove it meets regulations before the system can be commissioned. The test involves a high test current and not exceeding a specified voltage drop.

The important part is the copper wire PE from every socket back to the distribution board. I think it is not allowed any joints that can deteriorate.

I am not an electrician, so much of this is from reading what is around.
You need a qualified electrician to check your system. He may recommend improvements or he may condemn it until it is repaired.
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Last edited by AndrewT; 1st December 2010 at 11:19 AM.
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Old 1st December 2010, 06:35 PM   #5
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Right... I am pretty sure my landlords do not care.

The majority of sockets in the place do not have a three prong socket. A few do, and very few if any besides mine have it wired to the grounded conduit. (I installed a better socket and more in one location)

However I would like to point out my aims have little to do with the electrical system itself. Remember this topic is about preventing feedback and or burning off the attenuated signals.

Essentially I am wanting to either change the source of electrons for the attenuated signal or I want to flatten the signal. It matters not if it is changed from the 60hz it is now.
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Old 2nd December 2010, 04:54 AM   #6
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Borrow an isolation transformer and power all your audio equipment from it with all the earth wires single point connected back to the token building earth. That should fix your mess. Do not use a mains filter on the isolated side of the transformer, keep it on the mains side
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Old 3rd December 2010, 12:20 AM   #7
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In the US EMT (Electrical Metal Tubing) conduit is a permitted method of grounding outlets. This is a lighter conduit held together with set-screws, there is also a heavy duty conduit with threaded pipe ends. In any case EMT will carry much more ground fault current than a wire. The rules get interesting if a ground wire is run in the conduit.
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Old 3rd December 2010, 12:30 AM   #8
Enzo is offline Enzo  United States
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The other side of that coin is that a wire will usually maintain its integrity, while conduit clamps can come loose or apart.
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Old 3rd December 2010, 01:17 AM   #9
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The conduit does not give 115/120v in my building.

Borrow a transformer? Yeah maybe... I am more interested in developing ways to attenuate then dissipate unwanted signal though at the moment.
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Old 3rd December 2010, 08:13 AM   #10
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Quote:
Originally Posted by Destroyer OS. View Post
The conduit does not give 115/120v in my building.

Borrow a transformer? Yeah maybe... I am more interested in developing ways to attenuate then dissipate unwanted signal though at the moment.
That is what you are doing with an isolation transformer, massive attenuation. No need to dissipate it, why make work for yourself fighting a capacitive ground loop when it can be cut.
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