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Ground Loops explained


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Great discussion. How do battery based PSU fit into the ground loop equation? I'm think of supplies such as the SOTM battery PSU which has a 2-prong plug (so no ground)

 

The battery based PSU provides only power like 5/12Vdc. It does not provide an audio signal from a dac to an amp. Ground loops occur with signal cables of unbalanced designs where the source and the receiver are both connected to the safety ground.

 

If you use the battery PSU as is, it will not add or subtract to the existing ground loop problem, but, the AC charger depending on the design, can generate 50% of the AC mains on the output, and that's another dilemma and issue.

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This video only covers a small portion of "ground loops" and how they effect audio systems.

 

There was a wonderful paper on this several years ago where someone setup several high end home audio systems, with three pin AC, 2 pin AC, mixed 3pin/2pin, RCA interconnects, XLR interconnects and measured the heck out of them, seeing where noise entered the system, what caused it, how it was propagated etc.

 

The results of this flew in the face of conventional wisdom on the subject, the subject of the video, noise caused by safety ground potential differences turned out to be almost irrelevant in most "home stereo" configurations. The big culprit was leakage current through the power transformer to the chassis, this happens whether the plug is 3 or 2 prong. Because different boxes have different leakage amounts, there will be potential differences between boxes that usually cause current flow through the interconnect.

 

One of the interesting findings of this study was that in many situations using balanced interconnects made it worse not better!

 

Unfortunately I cannot find the paper on this study, I did some searching today and don't see it anywhere.

 

Note that this was standard good old fashioned audio systems, computer audio adds a whole new dimension to this, high frequency noise from digital systems behaves very differently due to the impedances caused by the inductances involved. I don't know of any study that has delved into this aspect with audio. There are lots of studies on high frequency noise in purely digital interconnect systems but I don't know of any that concern themselves with how the high frequency noise interacts with common audio interconnect systems.

 

John S.

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The battery based PSU provides only power like 5/12Vdc. It does not provide an audio signal from a dac to an amp. Ground loops occur with signal cables of unbalanced designs where the source and the receiver are both connected to the safety ground.

 

If you use the battery PSU as is, it will not add or subtract to the existing ground loop problem, but, the AC charger depending on the design, can generate 50% of the AC mains on the output, and that's another dilemma and issue.

 

Thanks. What is mean by the comment that I've put in bold?

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