Hi I just bought my first amp, Marshall MG15FX. Everything is ok except one thing: When I plug my phone to the audio input (the jack has iPod icon), it outputs the sound in very low quality, the sound some kind filtered or cutted off or something like that, there is almost no treble, mostly deep and low quality bass sounds. It does not matter using the amp's speaker directly or with the headphone, it is same. Is this a production problem or is that the best quality I can get with this amp, maybe its price scale, I dont know. I m suspicious about the jack input since there is no difference between the speaker and the headphone. Any help would be useful. Thanks.