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Wednesday, October 19, 2011
Bill Whitlock
10/19/11 10:12 AM,
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When a system contains two or more pieces of equipment that are grounded, whether via power cords or other ground connections, a “ground loop” will likely be formed. See Figure 1, below. Although ground loops often involve power line safety ground connections, disabling them is both highly dangerous and illegal. However, devices called “ground isolators” can be inserted in the signal path to break the loop safely. This approach attacks the problem at its fundamental roots, while tampering with safety…
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Wednesday, June 01, 2011
Mike Sessler
06/01/11 02:42 PM,
2 Comments
This article is provided by ChurchTechArts. The topic for today’s post comes from a reader, Jonathan Mould. He wanted to know more about the electrical side of sound. This is an interesting topic because sound is both electrical and physical. Sound systems turn physical movement of air into electrical signals, then process and amplify those signals (sometimes changing them into streams of 1s and 0s and back), and finally turn those amplified signals back into physical air movement. It’s…
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Monday, May 16, 2011
Bill Whitlock
05/16/11 09:13 AM,
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Previously (see here and here), we’ve looked at how unbalanced audio interfaces work, as well as how grounding-related noise can actually couple into the signal path. Of course, under fortuitous conditions, audio systems may be acceptably quiet in spite of poor techniques. But physics will ultimately rule and noises may later appear for no apparent reason – remember, noises that disappear by themselves also tend to re-appear by themselves! Most systems consist of more than two pieces of interconnected equipment,…
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Friday, March 11, 2011
Bill Whitlock
03/11/11 05:05 PM,
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While hum and buzz are often blamed on “improper grounding,” actually, this is rarely the case. Properly installed, fully code-compliant AC power distribution systems will develop small, entirely safe voltage differences between the safety grounds of all outlets. These normally insignificant voltages cause problems only when they couple into the signal path at a vulnerable signal interface. Let’s look at why unbalanced interfaces are extremely prone to this coupling and cause noise problems even when no safety ground connections exist.…
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Friday, March 04, 2011
Bill Whitlock
03/04/11 11:55 AM,
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“A cable is a source of potential trouble connecting two other sources of potential trouble.” The humor in this statement may be lost on those who regularly assemble sound systems. But a reality of sound systems is that a signal accumulates noise as it flows through equipment and cables. And once noise contaminates a signal, it’s essentially impossible to remove it without altering or degrading the original signal. For this reason, no system can be quieter than its noisiest link.…
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Wednesday, February 09, 2011
Bill Whitlock
02/09/11 01:29 PM,
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After teaching seminars for more than 15 years now, it still amazes me how many otherwise competent professionals don’t understand the importance of proper equipment safety grounding. Even more shocking (pun intended), many routinely and casually disconnect safety grounds to solve noise problems! Generally speaking, the purpose of grounding is to electrically interconnect conductive objects, such as equipment, in order to minimize voltage differences between them. National Electric Code (NEC) requires that 120-volt AC power distribution in homes and other…
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