persistent 60 cycle hum only on tube gear

@erik_squires said:

Supplemental ground rods must be bonded together with at least 6 gauge copper wire.  Running a wire from a branch circuit is not ok.

That is correct for a Supplemental ground rod. Not required for a Supplementary ground rod. For a Supplementary ground rod NEC doesn’t require any size wire shall be used. ( Note: Years ago NEC changed Supplementary to  Auxiliary because, for one, Electrical Inspectors (some?) used the code requirements for a Supplemental ground rod also for a Supplementary ground rod. Thus NEC changed the name from  Supplementary to Auxiliary. (See my post above on 01-21-2026 at 12:02pm

So the OP’s ground rod would meet NEC 250.54 code if the ground rod was connected to the wall outlet’s branch circuit EGC (Equipment Grounding Conductor.)

Auxiliary Grounding Electrodes [250.54], NEC 2023

https://www.youtube.com/watch?v=4a8Kh5aLCB0

 I have said many times on this forum, Lightning loves them. Your audio equipment electronics, not so much... 

Auxiliary Grounding Electrode NEC 250.54

Supplemental Electrode NEC 250.53(A)(2)

Could simply be mechanical transformer hum. Big trannys just hum a little into highly sensitive speakers. My Cary Audio 300B SEI and Willsenton 800i hum into Klipsch Fortes and Heresys. Both have massive power trannys and output 10-15 wpc. My Inspire KT-88 with smaller transformers is quite as church mouse but only outputs 6-8 wpc.

If the grounding electrode can ever carry power-system fault or surge current, it is NOT a 250.54 auxiliary electrode anymore, so for the sake of audio equipment grounds, no, you aren’t using an auxiliary electrode.  This includes anything that has conductivity to equipment chassis like your amp, cd player, etc. 

As I mentioned before, if you  are absolutely positively obsessed with the idea of an independent ground, you need your own power generation. Get a solar power bank hooked up to isolated batteries and then so long as your power generation and ground are isolated you are fine. 

@erik_squires said

If the grounding electrode can ever carry power-system fault or surge current, it is NOT a 250.54 auxiliary electrode anymore, so for the sake of audio equipment grounds, no, you aren’t using an auxiliary electrode.  

Erik, the branch circuit wiring EGC carries ground fault current back to the Grounded Service Entrance Neutral Conductor in the Main Service Equipment, electrical panel. From there the current returns on the electrical service neutral conductor to the Utility Power Transformer.

The Auxiliary ground rod is not involved.  It is not part of the ground fault circuit.

@erik_squires said:

If the grounding electrode can ever carry power-system fault or surge current, it is NOT a 250.54 auxiliary electrode anymore, so for the sake of audio equipment grounds, no, you aren’t using an auxiliary electrode.  This includes anything that has conductivity to equipment chassis like your amp, cd player, etc. 

Erik,

The earth shall not be considered as an effective ground-fault current path.

NEC 250.4(A)(5)

(5) Effective Ground-Fault Current Path. Electrical equipment and wiring and other electrically conductive material likely to become energized shall be installed in a manner that creates a low-impedance circuit facilitating the operation of the overcurrent device or ground detector for high-impedance grounded systems. It shall be capable of safely carrying the maximum ground-fault current likely to be imposed on it from any point on the wiring system where a ground fault may occur to the electrical supply source. The earth shall not be considered as an effective ground-fault current path.