AC mains noise Borrowed noise sniffer and tested my AC lines...

The device, Blue Horizon Mains Noise Analyser, is available in EU for Euro 657.02 to destinations outside EU  and Euro 795 with EU tax. https://www.kempelektroniksshop.nl/blue-horizon-mains-noise-analyzer.html I would think it is also available else where. That is the first Google to 'buy'                
I own a Furman REF20 several years old when I bought it used nine years ago on the goN' for $1,300? $1400.. close to that.. and I recently replaced all the OEM duplex in it and put in Furutech GTX. (But put the individual little piggyback filters from the OEM duplex, onto the Furutech same way as OEM.) Some GTX-D Gold, Some NCF Rhodium ((The PS Audio P-600 also has all Furutech duplex now)Noise at the extension cord duplex (where the actual cord to Furman starts) is measured at "297" The ONLY outlet I measured in the Furman, a 'source' 60v/60v balanced duplex measured at "032" the first time. No music playing. But system on. Second measurement twenty minutes later was "003" (I am thunderstruck.) Music was playing.               
PS Audio Noise Harvester: https://www.musicdirect.com/power/ps-audio-noise-harvester-blackI bought them on a sale where if you bought two or more, they all would be $50 each. That sale is over. I bought seven. i am using five. My spare two are not for sale! The are a little box  with 2 prongs for AC.. and they suck up the noise, and when the capacitor inside gets full of the noise energy, it blinks the diode sticking out the top. There are many variations from different companies. All the others more expensive. Even the Noise Harvester used to be $199. Then $99 Now it's at $75 a pop

Ok did all the baseline measurements.                  
At wall, nothing plugged in a 20amp single on a separate breaker: Noise "724" .That line is one phase sharing common neutral with other phase 20 amp for refrigerator. I wondered how much of a problem that ’common neutral’ made. Well almost zero!           
The stereo line at wall with frig ’on’ noise "724" (frig off ’710’ frig break off noise "711" so the frig is a non starter of a problem. VERY good to know.)              
Plugging in the two lines made up of 12 gauge MilSpec silver plated quad twist Teflon 600V wire. grounds run between the two quads. 34 feet and 44 feet to stereo area. From the noise readings, it is clear the quad twist all by itself is removing a good amount of the hash from the line.             
At the 34’ line end Furutech duplex (no Noise Harvesters) noise "432" With two PS Audio Noise Harvesters in line a few feet ahead of duplex measured at, noise "006"         
The other line for the amp at 44’ (With two Noise Harvesters in a duplex four feet from the measured duplex) the noise level "001"(amp not plugged in. for those tests nothing was plugged into any outlests except the Noise Harvesters.            
So outstanding noise reduction from the wall ("724") down to ("006") and ("001") on my dedicated line from the wall to the stereo.               
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Plugging in the PS Audio P-600 power regenerator to the 34’ line changed the measurement at the Furutech outlet to "036" with P-600 ’on’ (nothing in use via P-600) With TWO CD changers also ON via the P-600 the noise at the Furutech 34’ outlet changed to "040" So I consider that wonderful performance. None (well ,very little to me is as good as none) of the considerable previously measured noise from the CD players is getting BACK to the outlet via the PA Audio P-600 regenerator.               
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Adding the Furman power conditioner OFF nothing plugged into the Furman noise measured at the same 34’ line Duplex "063" PLUS AM radio noise on the test instrument. (the PS Audio was also already plugged in and ON for this test. so the Furman alone added only ((023)) on it’s own to the noise level.  When I turned ON the Furman REF 20 the noise dropped to "035" No AM radio noise anymore. (again, this is with the PS Audio plugged in too, so the Furman ON lowered the noise floor below what the PS Audio added. plus the Furman ON removed the AM radio noise on the line.)              
With Furman all electronics plugged on but those not turned on, only Furman turned on. At the 34" duplex noise measured "042"         
With all normal stereo equipment turned on the 34’ duplex measurement was noise "036" The items on included several preamps, and the Mrantz SA-10. (not turned on two Denon DVD players, The plasma TV. the Kuzma TT motor power supply I did not measure for those)              
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Small Adcom conditioner used for little stuff plugged in (with both big conditioners on at the 34’ duplex noise "060" plus AM radio noise.I removed the Adcom and substituted a Monster 5600 I own in it’s place, The Monster on with nothing plugged in gave at 34’ duplex "045" ... With all stuff plugged in in use (including the cable co boxes) measured at 34’ duplex "054" So I am leaving the Monster in            use.+++++++++++++++++++++++++++++++++++++++++++++++            
Finally my Audio Research SP-15 I had left plugged in at the 34’ box mainly due to the short cord. With it plugged in at the 34’ box at the 34’ box both conditioners in and on measured noise with Sp-15 in not ON "082" plus AM radio noise. ARC SP-15 ON measured "081" no AM radio noise. I removed the ARC SP-15 from that location and put back with extension cord to Furman. I did not measure anything when I did this.  
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as of now, my Rega turntable power supply wall wart sits with no place to plugin. Orphaned when I decided to plug the two PS Audio Noise Harvesters into that spot it had used...   
Also I do not notice the downside of using the additional Noise Harvesters in the 34’ line. Previously I had them AT the two duplex on the end of the line. This time I moved them to the single duplex at the 31’ point.on the 34' line.. similar to the amplifier line. Why this matters??? seems to.    
I have no magic comments on this stuff at this time. I just wanted to report the numbers.     

Use of the device while place is closed. Late Saturday until early Tuesday only.     
I am not going to bother test all day.. It IS Sunday. Only possible change might be on Monday.. But not much here. I might if I fel like it. But no way comprehensive checking.           
As for 'making the sound bad with PS Audio Noise Sniffers'. Yes, the can, location IS important. And the usual problem of lean sound due to too much filtering is well known to me. Any of the various filtering devices, overdone, can damage the sound. Mainly by making it thinner, tighter, leaner bass,.. You name it.      
The question: "What does it mean" Philosophical?? I guess what it means is the noise was lower at taht outlet at that time, curiously while music was being played.when music was being played. Period.If you cannot live without knowing why, you are SOL here.      
This Morning I an unplugging everything to get a baseline of the actual wall I take the AC from, and each stage asI plug stuff back in. Also searching for the 'worst offenders' injecting garbage back in. (Like the Laptop charger, known bad. And where the AM music is being injected on the separate Adcom power conditioner used for the cable and WiFi etc. Adcom may be moved off stereo AC? if it is not stopping this stuff.

As for sound.... I am now listening to Joni Mitchell "Court and Spark" a 'Target' CD. Her voice is clearer (easier to understand) than when I played it last night (without the two PS Audio Noise Harvesters on the Furman AC line) Also got to song with backing vocals, they a much clearer!  
I also switched back to the DH Labs/Furutech power cord to the Furman. which has more lower midrange and fuzzier vocals, than the Pangea AC14XL power cord., the Pangea is cleaer but a little leaner.  But I wanted to use my DH Labs again. It does take a few hours for the AC cord to really fully settle, even though it only moved inches. Plus not used for a few days.    (I am constantly flipping between them. Both are set at the position they can be plugged in anytime)   
The DH Labs cord is more musical. But as always, I am drawn to clarity. I will see if the added Noise Harvesters change the choice on a permanent basis. The sound is also more forward than before, more detailed in space.    I like it.
I also moved the Rega P5 power box. It has a LOT longer cord than I remember. So I can place the box on the TV stand, and the wart reaches the Monster PC.

When I swapped the OEM Furman duplex to the Furutech duplex, I realized I need to keep the OEM noise suppressors added on the back of each OEM duplex. Glad I did swap them over.   
I am happy I was able to do the readings. No problem to report them So it they help anyone decide what direction to go in... great. 
The one thing I had not realized is how some audio equipment removes grunge from the line. And others. particularly the CD changers just SPEW tons of junk. I should measure the DVD players... ?? maybe.. And the plasma, just to know, while I have the tester in hand.                         
One device I decided not to buy because the reviews said the wall wart spewed tons of garbage in the line. Since it was a reclocker to 'fix' problems.. LOL why add another problem when you fix one!All in all I an happy about my power stuff.

Another day. Very glad I borrowed the Noise Sniffer! Mainly adding the two PS Audio Noise Harvesters I had sitting unused on the 34’ line gave me some more detail. Also a little lean. pushed me to finally fix the tweaks to the Magnepan 20.7 midrange resistors.Sadly I did not realize the Duelund CAST resistor leads are very fragile. Bend then at the root more than a few times and they break off, no repair I can see. Lucky I had spares. So I also made the gizmo to hold them keep the leads straight, and no stress on them. I hope that solves them breaking . Sadly I had no idea they are so fragile.
Also the gizmos have coils on the 1/4" dowel to bring the 3/4" apart from speaker back to the 4.5" apart of the resistors. So they have no lateral pull. I used the space from the hole in dowel to the hole to the resistor to wind the 18g wire 27 times to make two chokes on the dowel. This to be like the ones I made for the tweeter. Seems to be helping. The detail now is striking!  So it works whatever it is doing...

The dealer I borrowed the noise sniffing device sells Isotek.I already had AC stuff. So I am not in the market. But he loaned me the gizmo when I asked, since I have been a customer for 35 years, and bought my Magnepan 20.7 from him.

spatialking.. thank you for the info.

Thank you, no bloodbath is way better than bloodbath. Specially when it is taking place in my bathtub.