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Acceptable Level Ground/Earth Noise

Hi Everyone
I have a dedicated earth for my audio system.  I was digging a bore for water and lost the rod so decided to dedicate that bore for Earth.  It is about 100 feet deep an is in water.  The line runs straight to my dedicated audio room and is shared among the various audio components.  
I am running a Clearaudio DC preformence through an Avid Phallus phone stage hooked up to a ML No.  38s pre.  The cartridge is a clear audio virtuoso MM.  The ML volume level goes to 92 and the hum appears at 60. Previously when the earth was shared the hum was almost unbearable at 60 but now is significantly reduced. 
My question is that is the hum just part of the analogue experience or should it be absolutely quite? 
srafi
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almarg
8,673 posts
 
I have also taken another wire and connected it to a copper bus bar to which the analogue equipment is grounded through individual wires such as the earth wire attached to the RCA wire plug the earth plug at the bottom of the table as well as the earth on the phono stage. All the 3 pin sockets are also grounded in the sockets as they would be normally....

I did forget to mention it gets louder when I touch the tone arm so could be something else.
What I would suggest trying, if you already haven’t, is disconnecting everything in the system from the copper bus bar, and connecting the earth terminal on the bottom of the turntable directly to the earth terminal on the phono stage. With that connection between the turntable ground and the phono stage ground being as short and direct as possible, and in particular not routed anywhere near your power amplifiers.

Also, if the power supply of what I presume is the Avid Pulsus phono stage (I’m guessing that your auto-correct software changed "Pulsus" to "Phallus") is located right next to the phono stage unit itself try moving them a foot or two apart. And make sure that all power cords are separated from the cable carrying the phono signals by at least several inches, and preferably more. If a power cord and the phono cable must cross at some point, have them cross at right angles.

If those things don’t resolve the problem, as an experiment try putting a cheater plug (a three-prong to two-prong adapter) on the AC power plug of the phono stage's power supply, to temporarily defeat its safety ground connection. Let us know the results if you do that.

Jim (Jea48), thanks for posting the Henry Ott writeup. I’ve seen that before and I always get a chuckle out of it, especially no. 8. For others who may not be aware, Mr. Ott is one of the world’s leading authorities on grounding and various other aspects of electronic design that often tend to be mysterious even to trained EEs.

Regards,
-- Al
gs5556
769 posts
 
Connect that ground to where the house ground and lightning ground are connected thereby creating a star ground. This way the voltages across the ground rods will be the same in the event of a lightning strike. As a bonus, the (somewhat) equal voltages will deter stray currents into the neutral and lower that hum even more.
erik_squires
5,268 posts
 
Srafi, you should follow local laws. If they are not enforced, you still should bond any ground to your service ground. Otherwise you defeat the purpose.

As for humming, start a new topic, but depends on your equipment, and if you have DC on the line.

DC can be caused by dimmer switches.

Here, the usual source of hum and ground loops is external TV like Cable or an antenna, and PC's. In both cases the best solution is a ground loop isolator.

Best,

Erik
jea48
2,944 posts
 

gs5556 said:

Connect that ground to where the house ground and lightning ground are connected thereby creating a star ground. This way the voltages across the ground rods will be the same in the event of a lightning strike.


gs5556,

I stand corrected. The lightning electrode system shall be connected, bonded, to the grounding electrode system of the electrical service.


Q. Please explain how I’m supposed to ground a service on a building that has a ground ring used for the lightning protection system grounding electrode?

A. If a lightning protection system is installed on a building/structure, it must be bonded to the building/structure grounding electrode system as per 250.106. The grounding electrode for a lightning protection system must not be used as the required grounding electrode system for the buildings or structures [250.60].

http://ecmweb.com/qampa/code-qa-grounding-lightning-protection-system

//


Principles of Grounding of Lightning Protection Systems per NFPA 7803.

Grounding

A. There are several types of lightning grounding, used separately or in combination, as selected by the installation contractor. Ground rods, perimeter (ring) bare wire, radials, plates, and concrete (rebar) encased designs all constitute acceptable earth electrodes. The lightning grounding electrode is a dedicated part of the lightning protection system. No other ground shall be used as a lightning ground (see section 4.13.1.3).

B. Other (non-lightning) systems requiring grounding shall be integrated (bonded or connected) to the lightning ground to form a common ground potential (see section 4.14). This is to protect electrical equipment from voltage rise mismatches where separate grounds are employed. Under lightning attachment conditions, the lightning ground will function independently of any other grounds. Should electrical system grounds not be connected to the lightning ground, the overall lightning protection system will still function as designed.

http://lightningsafety.com/nlsi_lhm/grounding_principles_NFPA780.html

For the US anyway, per NFPA780 as well as NEC 250.106 and 250.60.

If my understanding is correct each grounding electrode system shall have its own grounding electrode/s. The two systems are then connected, bonded, together. I assume by a minimum #6awg copper wire. In other words lightning rods cannot be installed and directly connected to the electrical service grounding electrode system. Is that your understanding as well? 

Jim

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erik_squires
5,268 posts
 
@srafi

Your utility pole does not provide a ground, it provides a neutral. It’s up to the service entrance to provide a suitable ground. You MUST bond ALL grounds together, and bond that to the neutral coming off the pole.

Having said that, you may use as many ground rods as you’d like. :) What you cannot do is arbitrarily use one rod for one room and another for the rest.

The reason for this is that is prevents the safety ground from working correctly. If a short develops to a case, and this independent ground rod is 10 feet from the house ground rod it can be many volts different than your neutral now. 10s to hundreds. It’s worse with dry soil.

The safety ground should guarantee that the case of your electronics is 0 volts, but if it's at some other, random point, it could be quite higher than 0. That's where you loose your life. :)
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