Instruct: Classify Amazon reviews into positive or negative sentiment
Query: poor FM sound

The Insten FM-10 I got has a extremely annoying whine that is present all the time. At first I thought it was a ground loop problem but the whine is present whether the car is running or not. Unfortunately the online seller I bought it from hasn't responded to any emails so I don't know if mine is defective or not. I suspect they are all of very poor quality and mine is representative. On the upside it does work well as a charger.