I am assuming the OP’s "dedicated earth" is not connected to any other grounding system in his house. Though he really didn’t say how the ground is connected to his audio equipment. Is the ground connected to the equipment ground terminal on the duplex receptacle/s that feed his audio equipment? Did he disconnect the branch circuit equipment grounding conductor from the receptacle/s? Or did he leave the branch circuit equipment grounding conductor connected to the receptacle/s and connect his "dedicated earth" directly to the chassis of the audio equipment? If he defeated the branch circuit equipment grounding conductor and replaced it with his "dedicated earth" connection it is surprising to me he has not lost any equipment due to lightning. (Lightning would/will flash over from his "dedicated earth" over to the neutral, " The Grounded Conductor", in his audio equipment as well as travel through the in wall branch circuit neutral conductor back to the electrical panel service neutral to earth again.)
Also if the branch circuit equipment grounding conductor was defeated the OP has eliminated the low resistive path of the branch circuit equipment grounding to carry ground fault current back to the source in the event of a hot to chassis fault in his audio equipment. In the event of a fault the ground fault current path will be his "dedicated earth" connection. Works great for hunting fish warms. Sucks for providing a low resistive path back to the source, the grounded service entrance neutral conductor.
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Even if the OP connected his dedicated earth connection (?) to the branch circuit/s equipment grounding conductor, making it an "Auxiliary Grounding Electrode", I would not recommend it... Even if it would/does meet NEC Code 250.54 Auxiliary Grounding Electrodes. It would only add a path for lightning to enter his house and fry who knows what besides his audio equipment.
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Mother Earth does not possess some magical mystical power that sucks nasties from an audio system.
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