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"Balanced" has nothing to do with equal voltages. Balanced is about equal impedances to ground. If the Corcom filter is fed from a balanced source, common mode signals of equal value would theoretically cancel to 0v at ground in the filter. If a Corcom is fed from a grounded-neutral 120v supply, the neutral is grounded at the source, where the hot side is not. (However, with the neutral grounded at the source, the common mode noise may not be equal on both legs in the first place.) If a "balanced" 240v w/neutral feeds the Corcom with equal impedances to ground, common mode noise can be cancelled at ground.

OK. Let's try to get to the source of this discussion. Any AC powered equipment will have to, as I have said before, deal with two types of noise, common mode and differential. If we start with the utility power transformer on the pole which is single phase, it is unbalanced at the primary, that is one side of the winding goes to one of the three phase hot leads and the other side to ground. However, coming off the secondary, the power is balanced with a center tap to neutral which is connected to ground. Ignoring for the discussion the warts in the transformers, the transformer cannot internally put out a common mode noise signal on the hot leads because it is balanced. The two hot leads of the secondary are always 180 degrees out of phase with each other otherwise your house wiring would not work properly. Each hot to neutral reacts to the differential voltage of the whole secondary and creates two voltages that are each half of the secondary (240 volts) and 180 degrees out of phase.

The utility transformer can and in fact does put out both differential power and noise signals. That noise will be highest line to line and half either line to neutral. So, when you are dealing with your line connected equipment you will have to deal with either the full differential noise coming off the utility transformer if it is wired for 240 or half the noise if it is wired for 120.

Since the utility transformer cannot put out common mode noise, where does it come from. Generally, it is picked up as RF noise on the lines either coming into your house or on the wires inside your house. Remember that devices in your house like motors can create differential mode noise feedback to the house power lines and also radiated common mode noise. If your device has a power transformer it will also reject that common mode noise to a very high degree. If it has a switched mode power supply the incoming voltage will be converted and filtered to DC which will then feed the switching supply, also removing incoming common mode noise. To supplement this rejection of common mode voltages which get converted to common mode currents, most competent noise filters like the Corcom mentioned utilize common mode chokes that reject common mode currents. A link to common mode chokes is included. Also included is a better circuit diagram. If you look at the diagram you will see that the filter first has a line to line capacitor to remove a lot of differential noise. Following that is a common mode choke to remove common mode noise. Then there is another line to line filter. Next is a line to line filter center tapped to ground which could further filter common mode noise to ground. After that are a line to line resistor, two chokes and another lint to line filter which I believe, although am not sure act like a pi filter to reduce RF effects that may have gotten through.

So, looking at this you can see that a filter like the V series Corcom can do a very effective job at reducing both common mode and differential mode noise regardless of whether the source is balanced or not. Also, with some of the suggestions of connecting one or more isolation transformer secondary connections to utility neutral defeats the main purpose of an isolation transformer, that is to provide safety from the secondary to ground. If you connect any part of the secondary to ground you are as likely to get a life-threatening shock as without the transformer.

https://en.wikipedia.org/wiki/Choke_(electronics)#Common-mode_choke
https://www.jensen-transformers.com/wp- ... ersion.pdf
https://www.jensen-transformers.com/wp- ... /an004.pdf
http://www.thatcorp.com/datashts/AES626 ... put_IC.pdf

I finished the rebuild with ground isolated sockets. I made sure of polarity integrity throughout. I also separated the secondary's with one socket on one secondary for 3.5A AC and the other secondary supplying two sockets just in case paralleling the secondary was the problem.
I still have the open ground probably because I did not follow Stu's schematic. I just want to know if I understand it correctly. The schematic shows the neutrals and grounds on the secondary side are bonded to house ground.
Since all grounds are bonded together at the chassis, then all I have to do is connect the secondary neutral to the chassis.

Yes.

thanks
but do i still have isolation

yes that works
i know you must think i am a bonehead here but
i will go through life plagued with these thoughts of why?????

finally

thanks all
I will do a listening test before and after
install to see if I can hear anything different

Ok put the iso back into the system
I carefully listen to a hires trak a Holly Cole
DSP 128 She has a deliciously smoky voice that tends to pull one into the song.
I listen "They Can't Take that away From Me twice through with no ISO, no 10ga power cords
then hooked up the iso with my 10ga power cords and listened again
if there was a difference I would lean towards the iso, but in a blind test I doubt I could tell you which is which.
ok as I was putting the iso back in I noticed this:

so the original unit was wired without the ground floating on the output side
and the unit probably would have shown an open ground.
confusion again
its dead quiet, probably better than it has ever been