Prob always there just can't hear it at higher volumes. Check the grounds of the amps an the Caps if you have them. Then check the preamp wires from the head unti to the amp. Keep it as shielded from power wires as you can. Some times tying a ground from the amp back to the head unit ground can fix a hiss or static
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Prob always there just can't hear it at higher volumes. Check the grounds of the amps an the Caps if you have them. Then check the preamp wires from the head unti to the amp. Keep it as shielded from power wires as you can. Some times tying a ground from the amp back to the head unit ground can fix a hiss or static