ok so i have and f 700 series, with an amp for subs and some Boston acoustics speakers.i used the good RCA and have well well ground, all cables have been routed correctly including i pod. So every time i switch track on the ipod source it makes a weird whistling noise and i will do it in the back ground but gets 30 times louder when i switch tacks, does not do it on cd or fm, and i tried unpluging the usb and using as an av and it doset make the whistling noise. What could it be? by the way i swaped the pioneer cable out this morning thinking it might be a faulty cables but it makes it exactly the same.

Which speakers does it come from? or is it just the sub?

Is the vehicle running or not?

no the speakers, usually all 4