Purchased in 2004 to protect the equipment of the governed against undervoltage ...
Indeed, some festivals located ultimately EDF no longer receive the 230 the night at 22:00, the voltage drops sharply when the water heater and others set off, and the lighting of the festival ... Briefly, 180V.
The amps do not care, they give less power, that's all.
But the board, some tables analog effects or do not like at all, begin to snore or worse, simply plant (if digital effects).
Nowadays, more and more power supplies accept 100V to 240V, in this case more problems. But this is not the case with all our gear, right?
So the solution I found is this power conditioner, which raises (or lowers if necessary) the mains voltage to bring it back within a few% decrease or increase acceptable to our gear.
Side benefit in case of bad connection (at 380V catch) it cuts out altogether, and it includes a surge protection / para-overvoltage.
To always be in a fly!
NB: there is a version 1200VA.