Goodwin's High End

 

AC Electrical System Design

In an ideal world, your local utility company would supply your home with electrical power in the form of a pure 60 Hz sine wave. We have sampled the power lines with an oscilloscope; they contain much more than pure 60 Hz power. Electric motors, fluorescent lights, computers, and other appliances contaminate your power lines and grounding system with electrical noise. In addition, other power-hungry appliances in your home such as heaters, hairdryers, and air conditioners will cause voltage fluctuations when they are in use. The electrical noise is not minor; it occurs in a wide bandwidth, up to several Mhz (1,000,000 Hz), and it contains large (several hundred volt) spikes and dips.

In order to isolate a high-performance audio and/or video system from these electronic "pollutants", and to provide the highest quality electrical power, we can take special considerations when specifying the electrical system for your room. Of course, we need to know where the electrical outlets should be placed in the room. This implies that we know the locations of the equipment and possibly the speakers. Sometimes it's wise to add extra outlets in case the furniture arrangement changes, particularly if the room has difficult access to fish new wires later.

Typically, we run separate, dedicated, isolated circuits for the audio and for the video systems. These circuits use high-quality special A/C receptacles with shielded electrical boxes in the walls. For the main equipment location, we sometimes prefer to have multiple gangs of receptacles in order to avoid the need for power strips. The receptacles are powered by electrical cabling in the walls. Typically we specify a form of shielded cabling or conduit to prevent electromagnetic interference within the walls. We also over-specify the capacity to reduce the voltage drop that occurs when current flows through cabling.

The electrical cabling terminates at your circuit breaker (or fuse) box. We have recently found new high-end circuit breaker boxes that use heavy-duty fixed breakers in lieu of the cheap pull-out variety. If possible and appropriate for your system, we specify these boxes as the connection is mechanically stronger and more positive. In the U.S., the power delivered to your breaker box is actually two "legs" of 110 volts each. This provides the option for high-current appliances such as dryers to use both legs for a total of 220 volts. Normally, electricians distribute the 110 volt circuits on both legs. To reduce the noise potential in a high-performance system, we specify that all circuits be powered by the same leg — preferable the one that has the fewest noise-generating appliances on it.

For some systems, we suggest a balanced power system. Installed either in the room or at the breaker box, this system lowers the noise potential by -6db and provides improved immunity from induced noise (known as common mode noise rejection). Recording studios often use these systems to ensure the best possible recordings.

Your high-performance system needs a grounding system not only for safety, but to prevent hum and noise. For safety purposes, almost any grounding system will do. For performance purposes, we prefer a low-impedance isolated earth ground. Isolating the grounds for the different circuits prevent cross-contamination of the electrical power. Isolating the grounds from the rest of the electrical system prevents contamination by other appliances. In some communities, the electrical code permits a totally separate, isolated ground rod installed in the earth. The electrician drives an 8' or 10' copper rod into the earth outside your home and connects your system's ground to it. He then connects the shielding on the electrical cable to the circuit box ground.

There is another level of grounding which goes even beyond standard practices. If you have a very high end system and would like the best possible ground—a customized grounding solution can be engineered for your home. This uses very high tech ground rods surrounded by a specialty fill which is mixed for the specific soil conditions of that particular site. These are placed in very large diameter holes which are dug sometimes deep into the earth. To keep the impedance as low as possible massive custom-made ground braiding are in essence welded into place. This welding is done using custom-molds engineered for each end of the ground braid to contain a controlled mini-explosion which welds the enormous ground braid to the super ground rod array. This is the last word in ultra-low impedance grounds. However please understand that going to this level can be rather expensive!

The techniques and materials described in this section represent the electrical infrastructure of your high-performance system. You may elect to include additional power filtering, isolation, and/or conditioning at the point of use within the room. This isolates each component from each every other component in the system (as well as from the outside world) thereby preventing cross-contamination of the electrical power. Because this additional equipment is not built into your home, this equipment does not necessarily need to be planned before the construction phase of your room.

During new or complete renovation, upgrading your electrical system will cost only slightly more than standard-quality electrical work. During minor remodeling or partial renovation, the labor costs will be higher if new wiring needs to be run through existing finished walls. We would be happy to consult with you to help you determine the best plan for your project.

 


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