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
@winoguy17 , that's a good thought. My SS amp has high gain and was boosting the noise level previously on a shared dedicated line. Since I moved my system to a subpanel with a line dedicated to analogue, the noise floor has been greatly reduced.
As a test, I hooked up an old Kenwood amp with much lower power and the noise from the mains was still present.

@yakbob , I tried a Jensen transformer between preamp and amp, but I have an Atma-Sphere OTL pre and the transformer ruined the sonics. I've seen some comments by Ralph(atmasphere) where he says putting a transformer inline with an OTL device can have unpredictable or negative results.

@lak , I like the concept of the iso transformers and looked at how you've implemented them. That type of setup would work in my basement, but cost is a consideration. I will ask my electrician about it and show him your pics, thanks.
@lowrider57 
How expensive was the surge protector with noise filtering? It would seem to be the right way to go, in my opinion.
@lowrider57 One must look on eBay but you can find used ones at a reasonable price. That's what I did.
What State do you reside in?
No need to filter at the breaker box!

Buy a Chang LightSpeed Line Filter which you can plug all your audio equipment into.

Has Digital and Analog AC sockets.

Does not limit current inflow!

Works great IMO!

http://www.changlightspeed.com
You may be right, gdnrbob. I think the surge/ noise reduction unit was about $700, but I have found some online for less. I get the feeling the electrician will only install the brands that his company uses. He had a binder showing the different units available.
However, he was fine with me providing the Romex and Hubbells for the installation.

@lak , I'm in Philly, PA (a row home). How did you determine the rating of the transformer (5 KVA) for your needs?

@don_c55 , thanks, but I've got a limited budget and I've already invested in Blue Circle and Brickwall PC's plus some Blue Circle line filters.