Ground Loops, Background Noise; Cleaning - Ecler AMI2-70 Notice D'utilisation

7.6. Ground loops, background noise

You must always avoid interconnected grounds between signal sources. It means grounds must
never arrive by two or more different ways, since this could produce "hum" ("ground loop") that would
even interfere with the sound reproduction quality.
Cable shielding, when connected to the chassis, must never be interconnected, so as to avoid
ground loops.
The AMI2-70/TR amplified mixer has been conceived to obtain the lowest possible background
noise. Independently of the electronic design the background noise will directly depend on the correct
use and installation of the mixing unit.
I. e.: setting a channel VOL to "2" and the output to "10" is not the same as the other way round. In
the first case, the signal coming to the mixing amplifier - which has got its own noise - is low, and so is the
signal-to-noise ratio (low signal). When the output amplifier boosts the whole signal we will get a very high
background noise. In the second case - with the channel fader at maximum - the mixing level is high, and
so is the signal-to-noise ratio. When the signal reaches the VOL OUTPUT and is boosted, it will keep a
much better signal-to-noise ratio than in the preceding case.

7.7. Cleaning

The front panel should not be cleaned with dissolvent or abrasive substances because silk-
printing could be damaged. To clean it, use a soft cloth slightly wet with water and neutral liquid soap;
dry it with a clean cloth. Be careful that water never gets into the unit through the holes of the front panel.
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