An RCD works by detecting the imbalance in the live and neutral currents to the tune of just a few mA. If you have a fault in your amp and say the live touches some part of the metal chassis, and assuming it is not earthed in any way (eg plastic feet), the chassis will be live. When you go to adjust the volume,nor touch the chassis, you will be diverting current from either the neutral or live away to ground, and it will trip the RCD and hopefully save your life. However, in old properties that use a fuse box, you do not have this protection and the result could be fatal so that’s why I say do not used ground lifters with non RCD equipped systems, or where you do not have the outlet equipped with a proper wiring code level safety ground.
I’ve been building amps for a long time but still don’t trust myself to build a double insulated amp. It only takes one mishap or sloppy omission and you have a non-compliant device. So the general approach I take is chassis is always earthed, do not build or encourage builders to attempt double insulated construction thinking they are safe, and finally try to avoid ground lifters where possible - but if you do use them, make sure they can handle the fault currents involved.
I’ve been building amps for a long time but still don’t trust myself to build a double insulated amp. It only takes one mishap or sloppy omission and you have a non-compliant device. So the general approach I take is chassis is always earthed, do not build or encourage builders to attempt double insulated construction thinking they are safe, and finally try to avoid ground lifters where possible - but if you do use them, make sure they can handle the fault currents involved.
There is an alternative.
It's a purpose made isolating transformer which separates the house wiring from the amp or other devices.
https://en.wikipedia.org/wiki/Isolation_transformer
I think so too, always ground a metal chassis to earth with a fixed connection in a self build amp....
It is not only a isolated transformer to get safety. Cables with voltages over ac 50 volts can be dangerous for somebodys life. I have used polystyrol for many times to isolate the amp on its ground plate. I case of fire polystyrol is flame retardant, but i fear about toxic fumes i error case..
The second reason of protection earth in an amp case is functional safety and EMC, only a metal case can deliver. Other marerials need measures.
My opinion...
Peter
Thanks for this advice Bonsai.
I just received one of these that breaks on 10mA (only one I could find).
https://www.amazon.es/dp/B098XC766Y?psc=1&ref=ppx_yo2ov_dt_b_product_details
I am now connecting my stereo via this one for more safety.
