Proper grounding will remove the NOISE
if you ground, It does not harm your amplifier
Because ..... at zero volume (in any player) input of any amplifier connected to ground.
Likly when player is off opsition (in any player) input of its amplifier connected to ground.
incase of AMPLIFIERS
INPUT CAN BE GROUNDED ANY TIME BUT,
OUTPUT SHOULD NEVER BE GROUNDED.
Secondly ALWAYS use heat sink for LM7805, (never ground input of lm7805 as it’s a Voltage Regulator not an Amplifier)
If LM7805 got burned then it act as open circuit, so no 5volt supply, player
would be off