Sam Lord wrote on Sat, 12 August 2006 22:43 |
In our all-unbalanced designs, we always separated earth/chassis ground from signal ground. Power supplies always had at least 2 secondaries on toroids to extract a center tap as the signal ground reference. Our noise was extremely low, even though cable shields were connected to (admittedly very-low-Z) signal ground. I expect that the same practice would be good for balanced gear, where signal ground inside chassis would be separate from the ultra-low impedance web of connected earth (single-point), chassis, and wire shields. However, I've read good safety arguments for a single-point connection of signal ground to earth ground at the quietest spot, like the facility's true AC ground point. Comments? Am I too far off topic? (Then please ignore...) Thanks.
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With balanced systems chassis earth and signal earth should be connected.
Because there is electrostatic coupling between chassis and the internal circuits, noise on the chassis can influence the audio signals. If you connect chassis ground to signal ground, the 0 volt reference (signal ground) fluctuates with the chassis noise and so the audio signal is virtually noise free.
It is essential that chassis earth and signal earth are connected only at 1 place. If there are more connections, noise will interfere with the audio.
Of cause signal earth can be split further into digital and analog earth etc... But they should only be connected at 1 point. This is known as the star grounding scheme.
There are 3 locations for connecting chassis and signal earth.
1 At the power supply output.
2 Between the power supply capacitors.
3 At the cable input where the cable shield is connected to the chassis.