Finally the ideal charger found

Very good, I find the solution with the rubber stoppers on the bottom of the charger, it does not slip and stands firmly on the wooden shelf.
RAVPower seems to build in a high-quality charging electronics, from all terminals come out the promised amperage.

I tested all 4 ports with an iPad Air, Galaxy Alpha S3 Neo and a RAVPower Power Bank.
I have measured with a PortaPow V2 USB multimeter, here are the results in detail.

iSmart Connection 1 - iPad Air 2.4 A, Galaxy Alpha 1.45 A, S3 Neo 1.0 A, Power Bank 1.45 A
iSmart connection 2 - iPad Air 2.4 A, Galaxy Alpha 1.45 A, S3 Neo 1.0 A, Power Bank 1.45 A
Connection 1 - iPad Air 1.2A, 1.2A Galaxy Alpha, S3 Neo 1.0 A, Power Bank 1.2 A
Connection 2 - iPad Air 1.2A, 1.2A Galaxy Alpha, S3 Neo 1.0 A, Power Bank 1.2 A

When charging, the voltage was always about 5 volts, even with a load of 30W charger was only moderately warm.
No noise, that housing is made of impact-resistant plastic, the workmanship is very good, all connections are straight and do not wobble.
The LED is not overly bright, that is also good.
I highly recommend this charger very, bought two more, so can charge all your devices to a charger, the whole family.