The headphone jack is an adjustable output, meaning that it’s affected by the volume control of the ipod. The dock connector will provide a consistent low level output, which is perfect for a powered stereo. If you had to use the headphone jack for some reason, make sure the ipod volume is set to 50% or less, and do the volume adjustments from the actual stereo. If you turn the ipod up too much, the input will be too powerful and it will sound distorted.