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RE: Really Victor? I didn't know that..

Posted by jea48 (A) on August 20, 2014 at 10:27:55

In Reply to: RE: Really Victor? I didn't know that.. posted by Victor Khomenko on August 20, 2014 at 05:40:47:

Simply disconnect the equipment from each other and then measure the AC voltages between their chassis and between their signal grounds, in many cases you will see significant voltages present. Sometimes because the signal ground is, in some way, connected to the safety ground, sometimes due to induced potential, but it is often there.

Agree.

But it should be said the difference in potentials is not always caused by the branch circuit wiring. Sometimes the potentials are caused because the primary winding of the power transformer of a piece of audio equipment was not checked for the proper AC polarity orientation when it was installed and wired into the circuit of the equipment. Due to coupling capacitance of the primary to the secondary of the transformer there is a very good chance there will be a difference of AC potential, voltage, measured from the signal ground of the reversed AC polarity of a piece of equipment to one that has its AC polarity orientation correct.

Sometimes the proper AC polarity orientation is caused from an improperly wired aftermarket power cord where the hot and neutral conductors are reversed at either the plug or the IEC female connector. Usually the reversal is at the IEC female connector.
Also an improperly wired AC power receptacle can have reversed AC polarity.

Wire and wiring methods used for audio branch circuits.

Quote:

The “Conduit Transformer”
• This finally explains what drives 99% of all ground loops!
• Load current in line and neutral produces opposing magnetic fields
since instantaneous current flow is in opposite directions
• Imperfect cancellation magnetically induces voltage over the
length of the nearby safety ground conductor
• Strongly affected by geometry and proximity of wires
• Highest voltages with randomly positioned wires in conduit
• Lower voltages with uniform geometry of Romex®
• Voltage is directly proportional to load current, wire length, and
rate of change in current or ΔI/Δt
• Mechanism favors high-frequency harmonics of 60 Hz
• For constant current in L and N, induced voltage rises at 6 dB/octave

The “Conduit Transformer”
Wires randomly positioned in conduit
produce the worst possible results!

Bill Whitlock, 9/4/2012 Overview of Audio System Grounding & Interfacing

Using the proper wiring materials and method of installation is important. Use NM cable (Romex is a trade name NM cable) or MC Cable with an outer aluminum armor jacket. This is a must for long branch circuit runs.
If using NM cable sharp bends should be avoided. Do not coil up any excess power cabling.

Putting in the sub-panel pretty much eliminates this.
Victor

A sub panel can be beneficial if the user has a place out of sight of the living quarters. There in a mechanical room. If installed in the audio listening room and the user later decides to put his home up for sale how will the appearance of the electrical panel appeal to a potential buyer?

And then there is the added cost of the electrical panel, feeder wiring materials, installation labor costs. Especially if the user only wants or needs 2 dedicated circuits installed.

• http://centralindianaaes.files.wordpress.com/2012/09/indy-ae   (Open in New Window)

Edits: 08/20/14 08/20/14 08/20/14 08/22/14

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