Installation of new AC lines......best way to ground to avoid loops and noise

@ jsautter


Mother earth does not posses some magical, mystical,  power that sucks nasties from an audio system


Grounding Myths

From Henry W. Ott’s big new book "Electromagnetic Compatibility Engineering"

3.1.7 Grounding Myths

More myths exist relating to the field of grounding than any other area of electrical engineering. The more common of these are as follows:

1. The earth is a low-impedance path for ground current. False, the impedance of the earth is orders of magnitude greater than the impedance of a copper conductor.

2. The earth is an equipotential. False, this is clearly not true by the result of (1 above).

3. The impedance of a conductor is determined by its resistance. False, what happened to the concept of inductive reactance?

4. To operate with low noise, a circuit or system must be connected to an earth ground. False, because airplanes, satellites, cars and battery powered laptop computers all operate fine without a ground connection. As a mater of fact, an earth ground is more likely to be the cause of noise problem. More electronic system noise problems are resolved by removing (or isolating) a circuit from earth ground than by connecting it to earth ground.

5. To reduce noise, an electronic system should be connected to a separate “quiet ground” by using a separate, isolated ground rod. False, in addition to being untrue, this approach is dangerous and violates the requirements of the NEC (electrical code/rules).

6. An earth ground is unidirectional, with current only flowing into the ground. False, because current must flow in loops, any current that flows into the ground must also flow out of the ground somewhere else.

7. An isolated AC power receptacle is not grounded. False, the term “isolated” refers only to the method by which a receptacle is grounded, not if it is grounded.

8. A system designer can name ground conductors by the type of the current that they should carry (i.e., signal, power, lightning, digital, analog, quiet, noisy, etc.), and the electrons will comply and only flow in the appropriately designated conductors. Obviously false."

Henry W. Ott

Right jea48. That's why I said it may or may not be better.

Right jsautter except unfortunately you have to slog through 43 pages to get to page 44 where finally they show what I clearly explained in far fewer words: plugging connected components into different outlets can cause noise. So plug all your gear into one circuit. Voila! No ground differential. No hum. Geez how hard was that?

millercarbon443 posts

03-19-2019 6:40pm

Right jea48. That’s why I said it may or may not be better.

Right jsautter except unfortunately you have to slog through 43 pages to get to page 44 where finally they show what I clearly explained in far fewer words: plugging connected components into different outlets can cause noise. So plug all your gear into one circuit. Voila! No ground differential. No hum. Geez how hard was that?

@ millercarbon ,

Please read pages 31 through 36.

https://centralindianaaes.files.wordpress.com/2012/09/indy-aes-2012-seminar-w-notes-v1-0.pdf

In most cases where the building electrical branch circuit wiring is the cause of ground loop hum it is due to the type of wiring used and or the type of wiring method that was used.

I have two 20 amp branch circuits, (10-2 with ground Romex), that are 75ft each for my 2ch audio system. My audio system is dead quiet. No ground loop hum whats so ever. No difference of potential, voltage, between the two equipment grounds measured at the wall duplex outlets.
Jim


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jea48

In most cases where the building electrical branch circuit wiring is the cause of ground loop hum it is due to the type of wiring used and or the type of wiring method that was used.

I have two 20 amp branch circuits ... My audio system is dead quiet ... No difference of potential, voltage, between the two equipment grounds measured at the wall duplex outlets.

I’ve had similar experience. My system is complex and biamplified, so it uses a bunch of dedicated 20A lines. Each amp is on its own line, plus there are separate lines for digital and analog sources. There are no ground loops.

millercarbon

plug all your gear into one circuit. Voila! No ground differential. No hum. Geez how hard was that?

It’s not that simple, because you can get ground loops even if everything is running on the same circuit. That’s because ground can also flow through interconnects and if they are different types, or have different lengths or impedance, you can have different potentials in the grounds, which results in hum. In some instances, you may need to use a grounding block to eliminate the noise, such as this. But as jea48 noted, the real cause is often the building wiring scheme itself.

Another key element to good AC is the use of tight, clean connections, from the receptacle all the way back to the service panel. I have also seen breakers with bad or corroded contacts - replacing them can not only reduce noise, but can also reduce their internal resistance and improve current delivery.

The two rows of breakers in the box, each row connects to one of the hot legs.

No, this is also mistaken. Typically, the legs alternate within each row. That’s how a 240VAC circuit is wired.

Whichever leg you use, make sure all your system components connect to that leg.

This is common advice, but it’s debatable. I have my digital gear connected to a different leg than everything else in the system. It seems to sound better that way, but I wouldn’t want to have to prove that to anyone.

I’ve experimented with putting each of my amplifiers on different legs, but couldn’t detect any difference.

Thanks for all for the advice and links!