Electrical isolation for A/V

On Wed, 31 May 2006 21:26:38 -0500, "Les" Gave us:

turning other items on or off in the house, do not affect audio (ie, such as ceiling fans or items like that).

heard others say that everything needs separate grounds. So what's the right approach to avoid any interference with audio/video equipment?

Put an exercise bike with an AC alternator hooked up to each one, and feed each unit its own power source.

Of course, you need lots of naked women on the bikes when you need it all fired up at once.

All that, just to watch a movie!

turning other items on or off in the house, do not affect audio (ie, such as ceiling fans or items like that).

heard others say that everything needs separate grounds. So what's the right approach to avoid any interference with audio/video equipment?

As a general rule and practice, AC circuits should follow the National Electric Code (or local variant) with standard safety grounding procedures.

Pro-Audio circuits are generally balanced mic level and line level signals that should be run in audio cables with a shield (audio ground) and drain wire. The connectors are typically XLR or Stereo

Whether the audio ground should be connected to the device or not depends on the circuit, the presence or absence of jack fields, etc. but generally there is a break in the audio ground connection either at the jack field or the device.

Consumer and Semi-Pro audio devices are often unbalanced (typically connected with RCA connectors). These are less desirable for long distances and sometimes more prone to picking up hum from external fields (especially if cheap cables are used). It's hard to avoid these since there are so many inexpensive devices that used unbalanced connections.

Microphone cables often require special consideration since the audio level is typical -40dB from a line level connection and more easily prone to pick up hum and noise from external fields.

Some Pros use a special balanced mic cable with 4 conductors and an audio ground arranged something like this.

• + - (Audio Ground/Shield not shown)

The beauty of this arrangement is that the geometry cancels the magnetic fields (both induced and projected) of the mics + and - connectors and the line is especially quiet when it comes to noise.

Keep any audio cables away from inductive devices (fluourescent lights, fans, motors, computer power supplies, transformers, etc. and you should be OK.

Of course the ultimate connections are now digital and fiber-optics in many cases, the latter having the advantage of not having any interference with AC circuits whatsoever.

Beachcomber

Use common sense. You don't want to run any audio cables parallel to power lines (such as wire tying them to electrical conduits).