Used a 2pin 250volt power cable with my Beyer A20 , caused Coil Whine(noise) ?!

[omidelf]

can someone explain this please ?

i bought a Beyerdynamic A20 amp , and one of the power cables were missing from the box (2pin cable) and since in my country power cables are all 2pins , they gave me A 2pin power cable from their shop(it was in their A2 box i think)

then i had some Coil whine issue when i played video games only , the higher the fps the higher the noise so i thought it was my GPU causing this

turns out that it was actually my power cable somehow!!!!!!!
when i used the 3pin version that was included in the A20 Box , and used a 3pin to 2pin converter , the noise was gone

so i have 2 questions

can this damage my A20 ? considering the 3pin cable is 125volt ? considering i'm using a 3pin to 2pin converter and the default power cable is 2pin in my country
and why did this happened ?

 

[xapoc]

There are appliances that require 2 pin and are better insulated and 3 pin which pin 3 is your ground and not so well insulated. Every country has different code for that hence the difference. Also having 2 pins is cheaper to run lines in different country's then 3 pin.

So with equipment being better grounded will eliminate certain feedback or interference.