Hi I do believe I read something before about there being a amplifier for the aerial which an after market head unit such as sony can't power. I have 99 A4 and in my previous 95 A4 I had perfect repcepiton with the same head unit. Can anyone tell me whether I definately need an adaptor for the aerial amplifier and how much it is. I asked in my local car audio shop and they said the aerial power feed output just turns it on off the loom, but this doesn't seem to work! Any help much appreciated!! Also has anyone else noticed that you get less bass from a sony cdx-mp40 head unit wired directly to the rear speakers than the standard concert head unit with active rear speakers.