Sound problem
 

hello there ,in the last 2 weeks i have a problem with my sound system,how my amplifier was burn out i put a nother one buy it from ebay
but after fitting in the car only my bluetooth works,i have been to audi to for coding but they say is no need for coding because the problem is the aerial
antenna.Is possible that my mmi system is not working because of that (cd dont work)

You need to do loop back testing and get a VCDS scan to determine where the fault lies. Start leveraging the SEARCH on how to do these, but here is one to get you started:

https://www.audiworld.com/forums/a6-...a6-c6-2884658/

as for what is component protected read through this: https://www.audiworld.com/forums/a6-...095-a-2918091/