Thankyou for your reply's jedinite24 and jafreeman, the plug and play sounds like a good idea.
12-30-14: Audiolabyrinth
Audiolabyrinth,
If you decide to try an isolation transformer you should first do a little research on the different types of isolation transformers and the proper grounding methods used for the output of the transformer.
An isolation transformer creates a new separately derived AC power system that is independent from the mains power of your home's AC power system. Example, if the primary winding of an isolation transformer is fed from the mains of your home, be it 120V or 240V, the output of the secondary winding will not have any reference relationship to the mains power of your home. The output of the transformer will be floating above ground so if you were to measure for voltage from either hot lead of a 120V out secondary winding to the earthed ground of you home you would measure zero volts. (I should note with a digital meter you may get a phantom reading, it is not a true power voltage reading.) So what you have is a separately derived 120V AC Isolated Power System, with 2 Hot ungrounded Lines, legs floating above ground.
NEC Code prohibits this type of power system to be used by non-qualified personnel. It should never be used for home audio equipment. Where this type of power system is used is in hospital OR rooms, ER rooms, and CATH Lab rooms, where electrical monitoring equipment is connect to a patient. NEC Code requires special Line Monitors to detect any power leakage to the ground plane of the room. For instance if a leakage of more than 4 milliamps is detected from any hot ungrounded conductor to ground an alarm will sound in the room and notify the medical staff there is a problem. The medical staff can then look at a milliamp meter and see how much leakage is present.The Line Monitor does not turn off the power.
It is also used in foundries where a ground fault condition could cause a loss of power. Again it is monitored by qualified personnel as well as Line Monitors connected to the mains.
Another place an isolation power transformer, configured as an Isolated Power System is used is on the test bench of an Electronic Tech. I have seen them used on the benches of hospital Bio Med and Bio Tech labs. Again for qualified professional use only. With this type of 120V Isolated Power System the unit just plugs into the 120V wall outlet and outputs 120V floating above ground AC power.
Plug and play? Be careful these are sold to the unbeknown general public through the likes of EBay and elsewhere. They are usually listed as Medical Isolation transformers.
Plug and play isolation transformers for the general public's use need to have a grounded AC output. This type of power system is called an AC Grounded Power System.
In the case of a straight 120V output one lead, leg, of the secondary winding is intentionally grounded and becomes the neutral conductor. One method used is to connect the lead, leg, to the metal case of the transformer. This common point will become the Star grounding point for the neutral conductor/s and the equipment grounding conductor/s for the connected receptacle/s. From this Star grounding point the equipment grounding conductor of the power cord that feeds the primary winding of the transformer is connected. This becomes the earth ground. From the same Star ground connection, a white color insulated wire will connect to the neutral contact on the 120V receptacle. Next from the same Star ground connection a green color wire will connect to the green equipment ground screw on the receptacle.
The remaining Hot ungrounded conductor of the secondary winding of the transformer will connect to the hot contact of the receptacle. (Note for larger VA rated transformers where the available power could exceed the rating of the receptacle, overcurrent protection would need to be added between the hot lead of the transformer secondary and the receptacle.)
If by chance you buy a plug and play isolation transformer with straight 120V out check the output with a three wire plug in polarity/ground checker to make sure the output of the unit is a grounded AC power system.
You can also use a volt meter to check. If the unit is wired as a Grounded AC Power System insert one test probe in the hot contact of the receptacle and the other test probe in the equipment ground U shaped hole of the receptacle, or the metal case of the unit. If the output is wired as a Grounded AC power System you will measure 120V.
From the neutral contact of the receptacle to the ground you will measure zero volts.
If you end up with a plug and play AC Isolated Power System isolation transformer you can easily rewire the output making it an AC Grounded Power System.
Note, an isolation transformer with its output wired as an AC Grounded Power System will yield the same isolation results as that of an AC Isolated Power System.
Also note, I did not mention the so called Balanced Power System commonly referred to as 60V - 0V - 60V. That would be another post altogether.
I believe that is what Jafreeman has .
.
Jim
