02-02-2013 12:31 AM
The company I work for recently relocated. They were going to scrap a 7' aluminum rack tower. .So I, got to take it home.
Before I get to powering up any of my rack gear, should I tie all the grounds to the tower?
Then, if the tower is connected to ground, should I set some some sort of insulation underneath the base of the tower so it is not directly on the floor in case of accidental spills or the rare occasion where water gets into the basment and gets the carpet wet?
02-02-2013 05:31 AM
Most rack gear is grounded together via their audio connections. Both low and high impedance connections should connect to frame ground inside the rack unit some place. Screwing the rack units into a metal frame also grounds the chassis of the units together so there shouldn't be any reason to go further unless some problem with hum arises.
Depending on the type or rack units, design, condition they may not like being on the same ground as all the other units. I have an old Yamaha effects unit or example that has a built in power supply that tends to hum more when Its grounded so I bypass the ground plug when I have it in a rack with other units. There's likely a defect in the power supply and I should open it up and fix it, but I don't use the unit a whole lot. So long as It functions properly I'm not too worried about it.
In your case you could ground the chassis but you'd have to ground all your gear to the same potential to avoid having a ground loop. I'd just let it float myself and seek its own ground potential via the rack unit chassis. Its possible to create a ground loop that can not only damage gear but be a rick of shock.
A ground loop works like this. Say you ground the chassis so there's zero resistance to ground. Its has the best path to ground possible being perfectly grounded.
Next you have other gear in the room, guitar amps, amplifiers, computers etc that are plugged into normal outlets. Those outlets have house wiring that go back to the fuse panel. The ground is provided at the fuse panel and you have maybe 50~100' of wire between your gear and the fuse panel.
This long distance of wire has more resistance in the wire so the ground isn't a low as the rack unit that has zero resistance. What you have now is a difference in electrical potential between the rack and other gear on a normal outlet. If you hold onto guitar strings plugged in and touch the rack you may have current flow and get a shock. Electricity will take the path or least resistance to ground. If the rack is grounded better than say your amp, your body provides the path to a better ground for the amp and you get zapped.
It may not be a shock either. Since these are rack units passing audio, and you'll have many cables from other gear, current may pass from one piece of gear to another seeking a better ground through the shielded cables. This can produce hum and noise in the signal wires and even cause premature component failure when your AC power has spikes or outages and the power supplies of your gear see spikes.
What I suggest is just using a power filter to plug all your gear into and try to keep things on the same outlets. If you find excess hum then troubleshoot the problem by process of elimination. Most racks like SKB cases have metal strips the rack gear mounts to via screws. Few need additional grounding. Just mounting the rack units in there provides the AC ground and grounds all the units together. If one chassis has allot of paint on it and isn't securely screwed into place so the ground is a little weak the others will likely have a good ground to the chassis so its no big deal.
02-03-2013 09:00 AM
So basically, it's just business as usual then. Pretty much what I expected. I just wanted to be sure.
I was mainly concerned that there might be more noise interference because the tower is made from much more metal then the rack box I currently have my components mounted in.
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