Malaysxi схема

Correct, the delta output is always the same. Wrong, there is no safe position as long you can not garantie what is live/phase or neutral! It can be swaped anywere, at plug, at outlet, distribution box, fuse box or even outside your house. No garantie!

I said there's no guarantee for safety. It's extremely dangerous, using this method. Did you use a translator to translate what I've written, because i did the same and probably what i meant is lost in translation.

Google translator App

I used it to. So nothing from the original meaning has been preserved :D

Accurate translation please.

Basically this is as good topology as any, it directly uses the mains to step down the voltage and power a regulator. This method is very lossy, with the 2.2k resistor alone dissipating 10W of power to power a single 40mW LED, but thia method uses no power transformers which are costy and bulky. Basically this method has been used up to the 1990s to power the CRT of TV's and earlier to supply the High Voltages needes by vacuum tubes. The biggest disadvantage is that the circuit is sensitive to how you plug in the mains. In one case everything will be fine, the chassis will be grounded and it'll work perfectly. The other way (click the switch) the chassis will be charged at mains potential which makes it essentially lethal to the touch. The circuit will still be working, because thw potential difference between the two rails will always be 17V (in this example), but the chassis will be connected to live and not ground making it lethal. I hope this clears it up a little

Using a power transformer physically (galvanically) separates the live and ground of the primary from the secondary, thus allowing you to chose a permanent ground position for your circuit, no matter how you connect it. This is the only way to galvanically separate the maina from the circuitry, capacitors won't do the job. Imagine this. In old TV's the chance is 50% that the chassis will be charged, so half the time when you connect a headphone 🎧 it'll become charged at mains potential. Imagine putting this on your head. It's like getting the electric chair :D. So they'd use an isolation transformer to create a separate ground point with a permanent position for the headphones to always be safe upon connecting.