I've searched around for this particular problem, but haven't really found anything on it yet.
The thing is, I recently changed the head unit in my car, an Opel Vectra B -00, and after that whenever I drive and listen to the radio, the audio changes from time to time, mainly it becomes more dull and loses the higher pitches. There isn't really any distortion and the volume is the same. This seems to happen more frequently when I start or stop, indicating a bad connection? The sound from other devices is just fine.
I use an adapter to connect the car's antenna cable (some kind of ISO-plug) to the DIN-socket on the head unit itself.
I've also tried to make sure the connection between the adapter and the plug is snug. It seems to be, I even put some electrical tape to make sure it's firmly in place. In the original head unit, a CDR-500, the antenna connector was held in place with some sort of clips. This one does not have them, but it still seems to be hooked on pretty well. The other thing I thought about, considering it happens more when I brake or accelerate, is that it has something to do with electricity, but since playing through the 3,5mm AUX cable works fine, I don't see why it would affect the radio.
Much text, might be that I messed up some connection type or such in the text so if it's hard to understand tell me. Thank you for your time.