Isolated Ground causes ground hum.

Check out the Ground Master box from Puritan Audio. It will cost you $165 you will just need to connect your ground wire to it. You can read Paul Rikby’s review.

Please don’t add any ground rods yourself. 
Have a licensed sparky do it. I’m sure it won’t improve your current sq situation. 

Don't understand why you would want to add ground.
If you live in the USA your household 120V power has a ground wire for protection from isolation failures as to make the breaker pop.
The neutral is connected the center-tap on the 240V transformer on the pole outside your house. 
The neutral carreies only current when a load is connected and will have a voltage potential to the ground in the outlet equal to the resistance dropout from the load current. 
This protection scheme can sometime cause trouble, and is one of the reasons balanced audio is used to explicitly avoid ground loops.
Leakage currents in high voltage transformers can also be a problem, and may leak into other windings on the same transformer.
You could try an ultraisolation transformer to isolate your neutral from the house neutral/ground.
I have 2000va Topaz transformer for this.
Adding ground rods nilly willy is not a good idea.

The problem is not the CJ amplifier, it's the extra ground. The earth is a poor conductor and that results in steady state potential in the ground -- which is the source of your humming.

An extra ground is not a good idea. Lightning surges isn't the only problem -- transient spikes occur all the time, such as utilities switching  capacitor banks and on-site generating facilities switching loads from utility to generators, any of which can produce transients to fry your electronics connected on a grounding system with a potential across it.

Hi everyone,
The humming problem is solved. I want to report back on what I have done to it.
1) Connected the ground to the conduit metal outlet box.
2) Connected the Isolated Ground (from my ground post) to the ground pin of the IGR receptacle.
3) The hot and neutral are connected as normal.
I changed the 4awg solid copper bare wire to 6awg insulated strained wire to match with the NEC code.
Result: The sound has improved by not a small margin. In all directions, soundstage, bass, image... you name it.
The only concern I have for now is how to protect my system from the lightning as Jim mentioned.
$100.00 well spent.
Calvin