why balanced power last before component?

Here is what Bill Whitlock has to say about a balanced power system.

Page 201
Quote:
Bill Whitlock, 9/4/2012 Overview of Audio System Grounding & Interfacing 201

So-Called “Balanced Power”

• Properly called SYMMETRICAL power
• Has very seductive intuitive appeal
• NOT similar to balanced audio lines in any way!
• Uses transformer having 120 V center-tapped secondary
• Both line and neutral output blades are energized at 60 V
• Although advertising often implies endorsement, NEC seriously restricts
its use – because it’s potentially dangerous!
• ONLY FOR PROFESSIONAL USE
• NOT to be used with lighting equipment, especially screw-base bulbs
• MUST have GFCI at outputs
• Only technical function is to reduce leakage currents
• Leakage currents are trivial system noise sources
• Reported noise reduction generally less than 10 dB
• Any real benefit likely due to its clustered outlets
This is an example of “marketing gone wild” if ever there was one!
End Quote
http://centralindianaaes.files.wordpress.com/2012/09/indy-aes-2012-seminar-w-notes-v1-0.pdf
.

^^ thanks for that, I did not find that in my search. Someone asked about balanced power on the OTL Asylum over on audioasylum.com, to which I responded:

One thing about balanced power- equipment is not designed for it. Here is an example:

If you are to meet UL or EU directives (CE mark), the fuse has to be able to blow to protect the user. The tricky area is what if the power switch, which is mounted to the chassis, gets shorted to the chassis and allows it to become 'hot'? The fuse will blow, because it is in series with the chassis. Now the same thing is true of balanced power.

But what if something happens such that the other side of the line shorts to the chassis? What then? There is no fuse for that. As best I can make out, in this situation there will be 60VRMS on the chassis- IOW it will be 'live', as in a balanced situation there is no 'hot' and 'cold'; both side are 'hot'.

As long as everything is working, balanced power offers lower noise if you have bugs in your equipment's grounding scheme. This is because if there is a grounding bug, there will be current in the ground connection. This can cause ground loops and in a really bad situation even damage something. Balanced power offers a solution for this. But ideally, there will be no appreciable current in the ground, because in a properly grounded audio system, the circuit ground floats at chassis potential, but they are not the same circuit- IOW its bad design practice to use the chassis for a ground!

A lot of audio manufacturers have not sorted this out, and it does not matter what field (pro audio, broadcast, high end audio) they are operating in. For this reason you will see some pretty respected names extolling the virtues of balanced power.

The part about there not being a second fuse is pretty important. In nearly all equipment made, there is an assumption that the 'neutral' side of the line as at ground. So if it is shorted to the chassis not much can happen- thus no fuse for that side of the line.

Balanced or more correctly, symmetrical power, is not anticipated by any equipment manufacturer or designer I know of. What this means is that if the chassis is shorted to the other side of the line from the fuse, 60 volts RMS (84 volts peak) will be exposed to the operator. If this occurs in the wrong environment and conditions, it could mean instant death.

Now you could have a fuse in the power circuit and that would be a good idea because if it is not there, the transformer supplying the balanced power will be damaged if there is such a short. But you would want to have separate fused outlets for each unit in use so that anything running on the balanced power would have protection for the user.

I've looked at several balanced power products and not been able to see any such fuses (which would have to be selected by the user) which suggests to me that they could be dangerous to use.

Atmasphere,

That is why NEC Code as well as UL requires the output of the balanced power system to be GFCI protected. Any imbalance of either hot conductor to ground will cause the GFCI to trip open. As little as 5 or 6 milliamps of ground fault current to ground will trip the GFCI open. Wonder how many guys here who wired their own balanced power systems are using a GFCI on the output of the transformer?

It should be noted that a GFCI will not operate as designed when connected to the output of an "Isolated Power System" (Floating above ground). An equipment ground is not needed for a GFCI to operate as designed, but it must be connected to a "Grounded AC Power system" to operate as designed.

Jea, technical verbage discrediting medical grade transformers is trivial here. When you're in hospital next then you can worry about them. :-) . Maybe invite Bill in to discuss the topic with you as well as he too obviously knows absolutely nothing about EQUITECH'S patents and products. "Shocking! ;-) ...(all tongue in cheek :-) But, I can't imagine what got into you and Atma; hope it passes.

Jea, technical verbage discrediting medical grade transformers is trivial here. When you're in hospital next then you can worry about them. :-) .
10-03-14: Ptss

Huh?

IF the transformer is indeed configured as an "Isolated Power System”, there in the output is floating above ground, the Isolated Power System is monitored by qualified personnel.
In hospitals Isolated Power Systems are used in ER Rooms, CATH Lab Rooms, OR Rooms, some X-ray rooms . Any place where electrical equipment or monitor equipment is connected to a patient.

.

Maybe invite Bill in to discuss the topic with you as well as he too obviously knows absolutely nothing about EQUITECH'S patents and products. "Shocking! ;-)

I suggest you climb down off your high horse and read the “EQUITECH'S” fact sheet on where balanced power systems can be used. A balanced power system is not to be used in a residential occupancy.

You will actually get better isolation from the mains power if the primary winding of an isolation transformer is fed from the two Hot ungrounded legs of the main service power, there in US 240V, and the secondary of the transformer is configured for straight 120V out with one lead, leg, of the secondary winding earth connected making that lead the neutral, the Grounded Conductor. The user will then have a new 120V separately derived power system.
Note. Per NEC Code the earth connection shall be made at any point of the grounding electrode system of the main electrical service.

.

...(all tongue in cheek :-) But, I can't imagine what got into you and Atma; hope it passes.
Ptss

Ignorance is bliss.
.
Jim