[quote="JunkyJan"]Good day gents (long time no speak!)
I have been wondering about the fervour around toroidal transformers in high-end audio. In my youth I was taught in technical school that toroidal transformers have a place in the universe (that being dictated by space and weight requirements - lower profile & lighter than EI etc) but also that the disadvantages outweigh the advantages... The thinking at the time being that a well-implemented EI transformer will always outperform a well-designed Toroidal. I looked at it again recently and came across this super-interesting article: http://www.soundstage.com/maxdb/maxdb071998.htm
There are some pretty large discrepancies in the article, at least as it applies to residential power the US.
a) US residential power is, mostly, split-phase 120/240 AC, 60Hz power. Not two-phase. There is some 2-phase, 4-wire power still extant, mostly in Philadelphia and Baltimore, but that is 180-degree power designed, far back in the day, to start elevator motors before 3-Phase Delta was common. To this day, other than shaded-pole induction motors, most single-phase AC motors require additional circuitry to start (motor start and motor run capacitors for instance). If they were 120-degree two-phase motors, this would not be an issue - but load-balancing would be.
b) This discrepancy demonstrates a fundamental misunderstanding of how a single-phase transformer works, and how "DC Offset" actually works. If there is DC offset, this will not be because of any unbalance between phases - as there is only one. The primary reason for balancing loads in a single-phase system is to reduce demand, and reduce the load on the neutral (ground). A properly balanced load under ideal conditions puts no load on the neutral. But, other than the potential to overheat the neutral from the panel to the 'pole' there are no issues with DC offset in a split-phase 120/240 system. Put another way, at the wallplate, the individual load does not understand, or care, whether the supply is 'balanced' or not.
Now, as to my opinion on conventional vs. toroidal transformers, I have none. But when I see some basic lack of understanding, I start to question the entirety of the premise and would tend to discount such a source. The Luddite in me leans towards 'old technology', but that is personal prejudice, not formed, fact-based opinion. I am entirely open to well supported opinions based on actual independently verifiable facts.