However, this alone may not be sufficient for a solid safety earth bond. All panels should be
earthed directly, either with their own direct connection to the earth tag on the power inlet, or
via the modular's earthed metal mounting rails and suitable toothed washer and screw. If you
have a wooden case with wooden mounting rails and you are toying with the idea of using a
mains transformer in your DIY power supply project then you may want to rethink your plans.
You will also need to provide earthing to any exposed transformer core. This does not apply
normally to toroidal types but EI types should have their metal frame earthed.
It is possible that by earthing the front panel you may introduce earth loops when you connect
your mixer to the sockets of one of the modules. The outcome of this is audible humming at
50/60Hz and its harmonics. It is produced by earth currents travelling down the screen of the
connecting cable(s). This can be avoided by careful studio wiring and/or by using balanced
audio lines to pipe signals to and from the modular and mixing desk. Most mixing desks will
have balanced outputs and inputs.
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