ive run into a bizzare problem. I recently got a alpine 9883 HU with the Alpine tua-t500 hd radio tuner installed in my car. However, it looks like the HD tuner bypasses the head unit's built in tuner, so when you are listening to a non HD station, the sound quality is worse than regular FM; when you do listen to a station that broadcasts in HD(or when the radio switches from regular fm to HD), the quality is amazing.

I would expect the regular FM should not suffer if a HD signal is not being broadcasted.