Wrapping up ground

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We've likely spent enough time on grounding and I wanted to wrap this up so we can move on to new territory. I had mentioned in yesterday's post the problem with cable TV and its ground interference with stereo systems that often causes hums and buzzes. If you do run into that problem you can always disconnect the third wire ground of your power amp with an AC cheater plug - but that's not always the best way to go. In fact, there would be many that argue it's not a good way to go at all, less safe than following the rules. The alternative solution is to disconnect the ground from the cable TV, but to do that you'll need an isolation transformer. The one I used to recommend was available at the Parts Express here, but I see it appears to no longer be available. Here's another inline version for less than $10 and looks similar though I haven't tried it. If you want the finest solution out there, you'll need to pony up a few bucks. Jensen Transformers makes the Cadillac of them all, known as an IsoMax, and is available here. Using any one of the transformers disconnects ground and galvanically isolates your stereo system from ground nasties provided by your friendly cable company. I had read somewhere that cable companies score lowest on customer satisfaction surveys, lower even than airlines whose customer service people are rumored to still wear clip on ties so they're not jerked over the counter by some irate customer. Here's some bottom line tips you can use for best grounding practices.
  • Star grounds are best. A star ground is a collection of grounds all meeting at the same point in a system. Most well designed audio equipment utilizes star grounding internally, but when you hook together products as a system, it's best to try and utilize one ground point if possible.
  • Dedicated AC lines form star grounds. In the PS Audio Music Room we have multiple grounded AC receptacles on dedicated lines. That means that each AC receptacle has its own wires running back to the central breaker box where the main ground is also located. If each piece of gear is plugged into its own dedicated outlet, then you've formed a star ground.
  • Plug equipment into a common plug group. A Power Plant, a power conditioner, even a well designed power strip all share a common ground. This helps keep everything on the same ground potential.
  • If you're really dedicated, run a separate earth ground. Not for the faint of heart, but if you've a dedicated room, it's good to have a dedicated ground stake tying it all to one point in a special conductive slurry pit, using exothermic welding bonds and so forth. Best to hire an electrician for this operation, because you want to be safe. You can refer your electrician to this document for guidance.
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Paul McGowan

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