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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.
lowrider57

Showing 4 responses by lak

lak's avatar
lak
4,714 posts
 
Probably not what you are looking for however I thought I'd mentioned it:
Somewhere after the sub-panel but before the AC outlet you might consider the installation of an isolation transformer 5 KVA each per dedicated line. This would be dependent upon your logistics because the isolation transformers will generate some heat and 60 dB of hum. 
In my basement, I had two isolation transformers in-between my main panel and sub-panel (feeding my sub-pannel) which gave me eight dedicated lines.
lak's avatar
lak
4,714 posts
 
@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?
lak's avatar
lak
4,714 posts
 
 A friend suggested the 5 KVA because he knew it was large enough for most audiophiles systems and would not bottom out. Other than that I'm not sure how to figure the needs but I'm sure other more knowledgeable people on Audiogon could assist.
lak's avatar
lak
4,714 posts
 
I agree, almarg and jea48 are a wealth of knowledge and willing to share.
Thanks guys...
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