Best way to eliminate "common mode" noise from AC

One possible way would be to add common mode choke. It can be done by making few turns (as many as possible) of the power cord on the large ferrite (chose one with the highest permeability). When wires in the cable carry current in opposite direction (normal/differential mode) magnetic flux is induced in the ferrite in opposite directions resulting in cancellation lowering inductance almost to zero. Common mode interference induces currents won't cancel, being in the same direction, producing inductance in series with both wires. This scheme works well at high frequencies only since it is difficult to put many turns of power cable on the ferrite. It is possible to build common mode choke for lower frequencies. It is pretty much 1:1 metal core transformer with identical windings connected as a common mode choke (in series) and not as transformer (in parallel). As long as windings are identical inductance for differential signal will be zero. I suspect that many power conditioners might have common mode choke in addition to normal mode filter.

Yes, common-mode choke or a balanced isolation transformer, appropriately sized for the load. A number of the "line conditioner" manufacturers like APC and Belkin PureAV employ common mode chokes in their products. I have been using balanced isolation transformers with great success over the past 8+ years.

http://i994.photobucket.com/albums/af67/mr_classe/General/belkin_zps16c121f8.jpg

http://i994.photobucket.com/albums/af67/mr_classe/General/APC_zpse05a8f0b.jpg

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A shielded isolation transformer can reduce common mode noise by as much as 12 dB. A balanced (60+/-) iso transformer can reduce common noise by as much as 20 dB.

Differential or transverse noise is more difficult to reduce but when it comes to power transformers, the idea is the opposite of audio transformers. You want limited bandwidth and a EI core is better than a toroid in this regard. Toroids are easier packaging and have less magnetic radiation.

Transformers are probably no more or no less effective than LP filters for transverse noise below 600 Hz, which includes several harmonics. Personally, more concerned with high frequency SMPS hash.

Thanks very much for your inputs.
I do use an Equitech 2Q transformer for common mode and some MIT products as well as good power cords and some enacom ac's.
Playing with what I have has proven that ac noise is a complex problem(at least where I live). I was hoping to hear of some new, or unknown to me, "magic".

The closest thing to "magic" may be power regenerators, like the ones from PS Audio and PurePower.

Thanks Gbart. I appreciate your taking time to be helpful but I mentioned in my initial query not including
power wasteful regenerators. I try to think green & buy the most effective,least expensive to maintain or operate, components. I think the Equitech 2Q transformer in a box & MIT combinations I use do an excellent job and are fairly economical to operate. So far I have never been able to justify investing even $3000 on a single conditioning/isolation component. But,I find isolation and conditioning extremely worthwhile and am seeking an ideal mix. I don't think a single component or brand will maximize results. AC noise is incredibly complex, and apparently growing moreso in microprocessor controlled robotics. My Spectral gear is 'very' revealing and cumulative rewards are proving satisfying & interesting. Hoping for more perhaps 'adding' a Shunyata or Sound Application product(s).
Need info/feedback. Thanks

Gbart is correct regarding PS audio, but if you are concerned why not go for balanced power?

Furman make some balanced power units. Remember the new PS audio regenerators are pretty efficient.

Chadeffect,

The Equitech 2Q that the OP has is a balanced power conditioner.

Roscoeiii,

Sorry I was meaning other balanced power units. Martin Glasband of Equitech known for his experitise with balanced power...

To add to my embarrassment I thought Furman made a balanced power unit that had a clever earth isolation system aside from the transformer LPF. (Not those 1 unit filters with pull out lights)

It was a few years ago, but I cannot find info on it anywhere. I was sure it was furman and that it was from their pro studio range and was a large 3 or 4 unit 19" rack?

Ah well. I would still go for the new PS audio regenerators even though the price is high.