One other thing you might try.....
I assume the two dedicated circuits and duplex receptacles are somewhat next to one another. A few feet apart at most.
You will need a length of bare #12 or #14 copper wire.
(Bare solid wire from a piece of Romex would do the job.)
The wire needs to be long enough to run from one duplex receptacle to the other.
* Turn off both circuits at the electrical panel.
* Pull the cover plates from the duplex receptacles.
* Loosen the 6/32 screws that fasten each duplex receptacle to the rough-in boxes. Bottom screws more so.
* Bend a hook on each end of the solid bare wire.
* Install the hook of the wire behind the duplex receptacle supporting strap, (bottom of recept.)
* Tighten back down the 6/32 screws making sure the bare solid wire exits down from the duplex receptacle supporting strap.
Basically you are tying the safety equipment grounds of each dedicated branch circuit together. Creating a closer star ground point ahead of your audio equipment.
Same thing Kirkus was describing in one of his posts
* Reinstall duplex cover plates and turn back on the two circuit breakers.
* Re-check for hum....
If the Hum is gone..... best you call back your electrician and have him tie the two safety grounding conductors of the branch circuits together in a more permanent concealed manner.
I assume the two dedicated circuits and duplex receptacles are somewhat next to one another. A few feet apart at most.
You will need a length of bare #12 or #14 copper wire.
(Bare solid wire from a piece of Romex would do the job.)
The wire needs to be long enough to run from one duplex receptacle to the other.
* Turn off both circuits at the electrical panel.
* Pull the cover plates from the duplex receptacles.
* Loosen the 6/32 screws that fasten each duplex receptacle to the rough-in boxes. Bottom screws more so.
* Bend a hook on each end of the solid bare wire.
* Install the hook of the wire behind the duplex receptacle supporting strap, (bottom of recept.)
* Tighten back down the 6/32 screws making sure the bare solid wire exits down from the duplex receptacle supporting strap.
Basically you are tying the safety equipment grounds of each dedicated branch circuit together. Creating a closer star ground point ahead of your audio equipment.
Same thing Kirkus was describing in one of his posts
* Reinstall duplex cover plates and turn back on the two circuit breakers.
* Re-check for hum....
If the Hum is gone..... best you call back your electrician and have him tie the two safety grounding conductors of the branch circuits together in a more permanent concealed manner.