can someone tell me what name of this part is? i am new to this site
From the two visible capacitors and seeing where the two cables go, it should be a whatever-to-5V voltage regulator…
i research a bit i think it is some kind of amplifier.can zynth work without that?i dont even know what inputs are down and how to connect cables from sound card for that.
I can bet much more than 2 cents that that part is not an amplifier: it’s connected to the external power socket and switch…
Anyway, this part is not a required one. Zynthian can works perfectly without it 
haha ok the less parts the easier to make for me 
can you explain what is purpose for this and how to connect i am no electronic expert i just know how to solder something
It is an adjustable switching regulator …you may use a variable voltage supply from 3.2 V to 40 V and obtain a 5V (in this case) or different from 1.25 to 35 V in output…is very confortable…
…but may be it introduce some switching noise
