Hey Hally. Glad I can help!
1. How long and thick do these copper rods need to be and approx how deep into the ground do they need to go?
The ones I use for this type of installation are solid copper (not hollow tubes!) about 1.5 m long, and about 1.5 cm in diameter. Bigger is better (but might be harder to work with). In Chile, you can buy them in most electrical supply stores. I would imagine that stores in your area carry something similar. Your electrician should know where to buy them. And you hammer them into the ground completely, the entire length. Nothing sticks up above the ground. You should even sink the top ends a few inches below the surface, in fact, and run your ground conductor underground.
2. At the back of the studio is my garden, can i put the rods anywhere, ie. out of sight behind a tree, do they need to be sheltered, etc?
Anywhere you like! They won't be visible, as you sink them completely into the ground, so you don't need to worry about hiding them or protecting them. It's probably not a good idea to put them too close to a tree, though, as you will probably hit a root as you try to hammer them into the ground. Just find some spot where the earth is reasonably soft, so you won't break your back with the hammering. Maybe a flower garden, or the edge of the lawn, or some place like that. It doesn't really matter where you put them, as long as they are completely buried deep down in the dirt, and have a good contact with Mother Earth.
3. How thick, what gauge does the copper wire need to be which connects the rods and runs back to the sub distribution panel... just to clarify,
As thick as you can afford! Ground conductor gauge is certainly defined by code for your area, but you can go BIGGER than that. They just give you a minimum acceptable. Bigger is safer. Bigger offers less resistance electrically, which is GOOD!. When I install machine rooms for video post houses, we use really thick braided copper cable for grounding the racks, about as thick as the cables that connect your car battery. If you can afford to use cables that thick, then go for it. If not, then see what code says, and double or triple that. You can always run several wires in parallel, if you can't buy really thick braided cable. In a pinch, you could use normal 3-core electrical cord (heavy duty) and use all three cores in parallel. That makes a great ground path.
The point is to minimize resistance, and give all that nasty hum and noise a real easy path out of your studio. Your electrician will probably look at you quizzically, and wonder if you are insane for specifying so much overkill in your grounding, but that's OK. It's your studio, and your hum, so you get to decide how much of it you want to get rid of.
You are refferring to the new sub distribution panel here?
Correct. Depending on how they wire things where you live, the sub-panel should already have a couple of long brass or copper bars in it. One is for your neutral bus, the other is for your grounding bus. The panels we get here in Chile have long pre-drilled, pre-tapped bars with screws in them: So there is a line of holes along one side of the bar for inserting the individual ground wires, and a line of screws along the top for holding them in place, then a lug on the end for connecting the conductor that goes out to the physical ground.
In some wiring systems, the neutral bus and the ground bus are actually tied together in the sub-panel or main panel! That might sound stupid, since one leg of your power is grounded, but it is actually a great idea: safer, and even less chance of hum. If your electrical code and wiring scheme allows that, then get your electrician to do it. He'll just install a thick jumper between the two buses in the sub panel. It might not be possible, depending on how things are wired and what code says, but if you can then do it.
In my machine room I will be running 4 seperate dual core PC's, Pro Tools, Giga Studio, VST's and another Giga Studio respectively. Again just to clarify, do the PC's come under "Technical"?
Yup! If it is part of your audio processing gear in any way, or even connected to it(!), then it is technical. So if you have a printer or monitor connected to one of those computers, the printer or monitor is also on technical power. Ditto if you have the computers networked through a router: the router is also technical. In short, if there is any sort of wire that connects two pieces of equipment, and one of them is technical, then the other is also technical.
The reason for all of this is to prevent ground loops. A ground loop is a situation where there are is a voltage difference at two or more points in your grounding system. If there is a voltage difference, then current flows. This usually happens when there are two or more paths to ground, and each path is at a different potential. So if you have, for example, a preamp plugged into one electrical outlet connected to ground point "A", and your console plugged into another outlet connected to ground point "B", then current will flow through the shield of the mic cable that you use to connect the preamp to the console, and that will cause hum. Or if you have your DAW plugged into your service ground, and your speakers plugged into technical ground, then once again you have a potential for current to flow through the shield conductor of the signal cable that connects the DAW to the speakers, and you'll have hum. Third case: Both your DAW and speakers are on the same ground, but the printer is on service ground: There is a potential ground loop path through the printer data cable to the DAW, and thus to your speakers too.
Just think in terms of: Is there any wire at all that connects your audio equipment to something else? If so, then consider either putting that "something else" on technical power and technical ground if you can, or using an isolation device of some type to separate the signals, such that there is no ground path. There are opto-couplers available for some types of signal, and isolation transformers for others. Infra-red links and radio links are also possible, but those are pretty exotic, expensive, and I doubt that you'll need those!
In any event, the point is to make sure that there is only ONE path to ground for your entire studio, and only ONE ground conductor from each wall box to that central ground bus. This way, when you connect a mic cable from the preamp to the console, both ends are at the exact same ground potential already, so no current flows in the shield conductor, and no hum! That's the object of the exercise: keep all of the grounds at the exact same potential, so that no current flows, and there is no hum.
Believe me, you absolutely do want to do this to eliminate all chances of ground loops and hum. If you don't, then tracing and fixing it later will be a nightmare. I speak from first-hand experience: Trying to identify where hum is coming form in a machine room is really, really hard, and solving it can be really, really expensive.
When using this method to run cable is it still neccessary to use conduit, ie. plastic pipe, if so what size pipe would you reccommend and thickness?
Once again, that depends on your local code. In Chile, conduit is required, but even if it wasn't I would still use it, for several reasons. First. it protects the wiring and cabling, but most important for me, it provides an easy way to
replace cables and wires, and to install new ones at some point down the line. If you have conduit, and you need to upgrade a circuit to handle more power, or replace a faulty wire or cable, then its really easy to pull the old wiring out, and use that to pull the new wiring in through the same conduit. if you DON'T have conduit, then you have the very sad task of contemplating making large holes in your US$ 5,000 soundproof studio wall... Install conduit for everything: You'll be glad you did. The extra expense is negligible, and the benefits far outweigh the cost. In fact, I normally run a few extra pieces of empty conduit, especially meant for future expansion. It's really cheap to do during installation, and really expensive to do six months down the line when you realize that you just have to have a ______ (fill in the blank) in your live room, and there is no way to get power or signals to it, since your existing conduits are full....
if so what size pipe would you reccommend and thickness?
I normally use at least 20mm conduit for normal electrical wiring. Code here only requires 10mm, but 20mm makes it a lot easier to pull wiring through, and leaves plenty of space for future expansion. If 20mm would be cramped, then go to 25mm or even 32mm.
And DO NOT USE ELBOWS! Just bend the conduit in nice long gentle curves. No tight corners. Tight corners are a death trap for pulling cables. They should be prohibited on pain of death. You can buy "bending springs" at most electrical supply stores for this very purpose: It's a very long metal spring, maybe 50cm long, that is slightly smaller in diameter than the interior of the conduit. You attach it to a piece of wire (so that you can get it out again after the pipe is bent), and let it slide down inside the conduit until you get it to the place where you need the bend, then you gently warm the conduit (I use a small propane blowtorch on a very low setting, playing it back and forth slowly over the conduit) until the plastic becomes soft: Then you bend the conduit to the shape you want (the spring prevents the walls from collapsing or pinching), hold it in that position for a few seconds while the plastic cools and hardens again, then you use the wire to pull the spring out. Presto! Instant gentle bend! That might not be the way to do it where you live, but it is prety much standard here.
Use the largest conduit (within reason!) that you can afford, and that fits in your wall / floor / ceiling while still leaving space for acoustic treatment. At least 20mm for electrical, and bigger for signal and data. Oversize always!
Don't forget that "conduit" is an open pipe, and sound loves to travel down open pipes. So any conduit that links two rooms in your studio, or that runs from outside your studio to inside it, needs to be plugged somehow at both ends (but not permanently!), and needs to have a couple of bends in it, even when they are not needed to get from "A" to "B". No straight pipe runs: always throw in a few curves.
Hope that helps!
- Stuart -
