The sub-woofer "crackle" can be wiring. I would check your wires to not only your sub-woofer, but the speakers as well. Some technicians do not understand the importance of polarity is wiring the speakers.
As to your TV output to the radio for surround sound, there must be an outgoing connection from the TV's tuner back to the radio for this to work. My TV has a left and right "RCA" plug to do that and it is wired to the AV2 input on my Concertone.
You should look at the connections on the back of your TV to see if there is not only a yellow RCA plug to your "composite" video input, but a white and red connection from your TV audio output to the radio.
A photo of your TV's connections and the model of your radio will be helpful to let you know how to proceed.
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