New Dedicated Line - Almost No improvement

If you say you have a dedicated line and are getting noise from the AC then you dont have a true dedicated line. A true dedicated has to be brought in independent from the street. At the very least you are sharing a ground on your dedicated line.

A true dedicated has to be brought in independent from the street.

Good luck getting that...

At the very least you are sharing a ground on your dedicated line.

Per code the EGC (Equipment Grounding Conductor) of a branch circuit shall be ran in the same conduit or cable and connect the equipment ground bus in the same panel the branch circuit originates.

Exception, when a branch circuit is fed from a subpanel where an isolated ground receptacle is used an insulated isolated ground EGC can be extended and connected to the main electrical panel equipment ground bus.

No dedicated isolated ground electrodes allowed... They serve no purpose and can be electrically dangerous to life.

An Auxiliary ground rod is acceptable per NEC provided it is connected to the EGC of the branch circuit wiring. (NEC 250.54)

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From Bill Whitlock,  (https://www.prosoundweb.com/author/bill-whitlock/)

"In reality, most of the reports of fantastic noise reduction attributed to earth ground rods are actually the result of the separation of various ground wires and their connection to a single point. It is the separation of the ground current paths that eliminates the common-impedance coupling of noise from noisy equipment into quiet equipment. It is extremely rare for an additional earth ground connection to solve a noise problem."

Fact!
Mother earth does not possess some magical mystical power that sucks nasties from an audio system.


Grounding Myths

"Electromagnetic Compatibility Engineering" by Henry Ott

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

My ground rod is bigger than your ground rod.😁 Fact. In the interest of getting the best, most consistent ground, I used the 25 ft long/deep iron drill pipe for my water well. Damned thing is very thick, and hard to drill a hole for the bolt used to connect the copper wire to. Now it is a done deal, and I don’t worry about having a good enough AC ground for my panel.

 And yes, it is only a couple of feet from the electrical panel.

@jea48 , while I agree in principle that an earth ground connection is generally not the cause of noise, it is not always not the cause, and when one considers emitted EMI, it can be critical. The earth ground connection (in theory) holds the metal in the equipment, cable shields, etc. to the same potential as earth, but we can call it a ground plane. Now as noted, that connection is more than just cable resistance, it is also impedance. If you remove the earth ground connection, then all the metal floats, and it floats in comparison to earth ground, which means you have a capacitor to earth ground and a "new" path for EMI that you would not have if connected to earth ground. This will never be an issue at analog audio frequencies, but it can be an issue at higher frequencies even with the higher impedance to earth ground.

You know what is really foolish? Those ground boxes filled with dirt that don't connect to anything.