this cirquit rectifier can be used as a symetrical power supply with
+ 2 time the efficient voltage and
- 2 time " " " " "
or depending on who we place the ground
+ 4 × the efficient voltage
the two diodes (full top and full down) are not requered, these shortcut the system at the begining to solve the negative charge of the first capacitor
if these capacitor have polarity, is better to have it
