^^ 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:
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.
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.