People get confused when comparing ships to land based (e.g. building) grounds in which two or more grounds in, say a building's earthen foundation, could have very different potentials for a variety of reasons and thus ground loops can be present in shielded cables grounded at both ends. On ships, however, unless there is some strange disconuity, the ship's hull is a common potential and generally no ground loop will be generated, so you can generally have a doubly grounded cable with little risk of organic noise.
One thing I've always wanted to know: Where is the actual "ground rod" in a building/residence? How do I find it? I've assumed it was just the water pipe, but now I am not sure.
Also, don't these rods get corroded to oblivion after decades in the ground from electo-chemical reactions?
5 years ago I built my house and did my all my electrical, I needed a Ufer ground in the foundation and 2 ground rods near the meter. Being a newer area, water lines were plastic.
Rods definitely do corrode and need to be replaced regularly. ~10 years for zinc coated steel and ~40 years for copper coated steel rods.
They do get corroded and are supposed to be replaced every so often. Different materials are used depending on the type of soil to minimize the corrosion. If they're really fancy they might have a cathodic protection system to prevent corrosion.
The water pipes are not metal at our house, so they would be of no use as an electrical ground.
This was in 2014, in Poland.
- Have a central grounding point - a steel car body has higher resistance than copper wire so using multiple ground locations will introduce voltage differences.
- Use a large gauge stranded wire for your ground.
- Use the same gauge wire for the ground as you did for the power wire.
- Keep wire runs short.
- Use twisted-pair wire for audio connections.
So for a multi-amp system, you'd run a large gauge wire from the battery positive to a distribution block, and from there to the head unit and amps. The ground from the head unit & amps would use the same diameter wire and be run to a central point. The ground strap from the car body to the battery negative post would perhaps be upgraded to the same diameter as the positive wire.
He is using ground loop isolators because of the length of his cable runs. In a car, that's not a problem as anything over 3 meters would be rare.
Single point grounding makes sense, because as I said, steel is a worse conductor than copper, so you'll end up with a voltage difference between your grounds (from each to the battery) if you use more than one.
So far as twisted pair, he strongly suggests using them to provide shielding against magnetic induced noise. They also provide good shielding against RFI - remember you've got 4-8 spark transmitters running at 900 to 5000 rpm interval in the engine.
And using the same size wire for both power and ground makes sense because different gauge wire has difference resistance.
The author, Bill Whitlock, is the president of Jensen Transformers, makers of high-end audio transformers.