Last post/update for now
After reading the first reply, I redid all my joint and double check all the wiring.
Resistance and voltage checks were good.
I plugged the amp through an extension cord to test with headphone, I still heard loud buzzing.
I suspected that the extension cord is at fault, therefore I plugged the amp straight into the wall outlet.
With just headphone connected, all buzzing noise went away and the amp is dead silent.
So Buzzing was due to extension cord.
I am wondering if extension cord is the culprit for both the buzzing noise and the shocking, perhaps due to bad ground?
I didn't do anything more with the amp, because I am treating the top of the case as a possible shock hazard.
So is there anyways to test the top of the panel without touching it?
I am too scared to do anything more with the amp currently, really wished I could listen to it instead of being fearful to it
P.S. Is it normal to hear a crack/pop sound from the headphone when plugging in to the amp.
Thanks and sorry for double posting.
Just panic and impatient and didn't know what to do.