Several drivers have intensity regulation.

Also possible to do pwm control.


With a power outage, everything is black and the audience do understand why they will not get any performance. When some equipment is broken, the audience will think: So why didn't they have spares - aren't we important enough. And the musicians will think the public is unfair, and instead try to focus their frustration on the specific equipment - or the supplier of that equipment.

When they notice the problem with a broken brick 30 min before the event, but manage to get everything going again by picking up another power brick, they will just get an adrenaline kick and then a funny story to tell over a beer. When their equipment goes up in smoke or just refuses to power up with the power bricks they can find, they will not remember the event as a funny anecdote but will tell other musicians about their experience. So even if they are responsible, by just forgetting to bring the correct brick, they will still blame you if they can't get the equipment running with other similar power bricks.

Next thing - if your power brick have a long cable, then you have multiple possibilities that someone drops something heavy on the cable and shorts it. Or someone get their foot snagged and rips out a wire. When something bad happens that kills the mains, then they can often get help from the people responsible for the premises to replace a fuse. And when the city gets pitch black because of a major power outage, no one will blame you. Your consern is the cases that may reflect back on you.