u/Firm_Big_

I recently picked these up for my cousin for a few bucks. They sounded perfect in his car and had no problem but the shop installed them in my truck and I'm hearing audio hissing with the following turn down and the radio off even when the radio is on I hear at low volume. the power is ran on the right and and the av cable is on the left. The shop charge me way much and now they want to install a knob for $30 to remove it. what could be the real problem. When I'm ready to remove these I don't wanna hear static at low volume...