Isolation transformer question

I have an Audience AR6 power conditioner. I bought it three houses ago and it made a positive difference. I moved from the big city to a brand new subdivision on the edge of farm country. The people across the street had Moo Cows and the next house rotated crops. Anyway, there, the power conditioner seemed to do absolutely nothing. I left it in for the magnetic circuit breaker, but that’s it.  8 years later, I’m back in the big city and the AR6 makes a very noticeable difference.

YRMV

There are plenty of good reasons to use an isolation transformer including blocking DC, preventing ground loops and getting a quiet neutral. Of course the biggest variable is the quality of your AC in the first place, which is my case is just dreadful. (The corporate parent of my electric utility has paid tens of millions of dollars in penalties for its bribery and fraud schemes, which only drains money that could be spent to improve local infrastructure.)

You need to know that isolation transformers hum. I threw out a 2kv Soundtrapper isolation transformer because the noise of the hum more than counter-acted any perceived benefit to the electronics’ noise floor

lloydc

You need to know that isolation transformers hum.

Mine don’t.

If there’s a hum, that most likely indicates that there’s a gremlin somewhere else in the circuitry. Possibly a grounding issue.   Yet, poorly made transformers can hum - if the windings are uneven or if the lamination deteriorates.

@ steakster, you are fortunate.  It is my understanding that the larger the iso transformer, the more likely it is to hum.  IME, there is always some hum on very large whole-house transformers, but they are located outside or in their own room, far from a listening room.  They could be very useful (I think @whart and M Fremer had some installed). I had two "audiophile" transformers, and kept the smaller one (which I use on front-end components with no problems).

A cursory search on Google confirms that transformers hum by nature, e.g: 

"There are actually multiple causes of transformer noise. The main one is the Magnetostriction Effect. This is when the current that flows through the transformer’s coils creates a magnetic field. The magnetic field then changes the dimensions of the transformer’s iron core. The core expands and contracts with the alternating current, which causes a humming sound."  Landmark Electric Inc.

Perhaps one based on a toroid would hum less?