Dedicated Line Noise Filter?


I don’t know if what I’m seeking exists, so I’m asking the experts.
I have 2 dedicated lines installed; one for analogue, one for digital. They originate at a sub-panel off the main circuit box. The sub-panel is connected by the hot lead and has it’s own ground including a second grounding rod. There is a home surge protector installed at the main circuit box.

I have passive conditioning on both lines for the components, yet I’m still hearing noise thru the speakers (from about two feet away). I live in a city and I suppose it could be dirty power from the grid.
Now to my question; is there a noise filter that can be installed at the site of the circuit panels? My electrician offered a surge protector with noise filtering (plus EMI/RFI), but was very expensive. So, is there a device that can be installed upstream to lower the noise floor?
Many thanks.
128x128lowrider57
lowrider57
... In Philadelphia, a permit is not required for an electrical addition or upgrade in a residence.
The law states that an inspection is required at the time a house is being sold.
Sorry, but you’re mistaken.

" Electrical permits are required for the installation, alteration, replacement or repair of electrical and communications wiring and equipment within or on any structure and for the alteration of an existing installation. "

see: https://business.phila.gov/electrical-permit/

That your contractor didn't know this - and didn't insist on applying for the required electrical construction permit - raises questions about his competency, and whether he's even licensed to perform this work.
I agree, almarg and jea48 are a wealth of knowledge and willing to share.
Thanks guys...
Cleeds, that's interesting. The company that I use has about 20 electricians on staff. They come to the house to give a free estimate, then return about a week later to do the work. Perhaps they get the necessary permit before starting the job. Maybe someone in their office does this.
This the third time they have done work for me; an upgrade with new breakers, lines and receptacles, then my first dedicated line after I entered this hobby, and the latest work 2 weeks ago.
lowrider57
The company that I use has about 20 electricians on staff. They come to the house to give a free estimate, then return about a week later to do the work. Perhaps they get the necessary permit before starting the job.
The permit is held by the property owner or occupant, not the contractor. When the work is complete, the project should be inspected in accordance with the permit, and an approval sticker affixed at the site. If you don’t have these permits and stickers, the work was not done in compliance with your local code: Code requires the permit and inspection.

Please don’t take my word for this - contact your city’s construction department for details. And while we're at it, please share the name of the electrician you've been using.