Balanced vs standard power

Used both balanced and isolation with general purpose step-downs and various others.

http://mysite.verizon.net/vze22yzp/id10.html

For amps in general, never found much benefit for balanced AC. In fact, my Plinius amps are completely indifferent, other than needing a stethoscope to detect any noise, but I still keep them on a 60/60 diet because it doesn't do any harm. My Genesis 1600W bass amp is the only piece plugged direct to "the wall". For class A/B or D amps, even with 10X capacity, a transformer can still be a "speed bump" because those amps recharge capacitors in less than a cycle. Class A amps, with a steady amp draw, are a good load for isolation transformers.

On the other hand, preamps and sources have responded well to balanced AC. In some cases, like the SFL2, which has a power supply larger than many amps, the difference was shocking (sorry, bad pun).

Agree with Zman that multiple smaller isolation transformers are better than one. That is the point of isolation. Do you realize the weight of a 15KVA transformer?

Code issues with distributed (through wall) balanced AC that Equi=Tech has dealt with but that doesn't apply to boxes in room or on the rack.

There's also the running cost. Although they're quite efficient under load, they have an "idle" or exciting current (typically 10% of capacity). Although larger transformers have a lower percentage of exciting current, it's always more.

Gotta disagree with Jeff about the Sola CVS (and MCR) regulated transformers. They are great for their intended purpose but they're noisy and don't respond well to dynamic loads. The CVS series provides less isolation and noise reduction.

Prefer standard EI core transformers rather than toroidal for this purpose even though toroids make for better packaging. Enough online and archived discussions about this already.

Saw a NIB Signal DU-10 on Ebay for about $1200 (retail) and there's pages full of 5, 7.5 and 10 KVA GP step-downs (240V required) under $500. Doesn't sound like cost is an issue for you. Just gotta say... there's good power and better power but ain't no such thing as audiophile power.

Wish it were that simple but there's more to those than just a transformer. As part of the ferroresonant design, they are partially saturated at all times. Along the same lines, in regulating voltage, amperage can suffer. So... with a dynamic load, they have to be oversized to a larger factor . While the CVT series has better amperage stability and tighter regulation, they're more like autoformers so noise reduction is one third of the MCR and a true isolation transformer.

Don't get me wrong, for decades they have been the 'king of the hill' as far as fast, reliable regulation and only recent, advanced electronic tap switchers can compete for the throne. They're also heavier and expensive, except for that used, $20, 1000W MCR portable I bought once.

Interesting question about the harmonics. Personally have doubts about any kind of harmonic filtration below 1 KHz for any passive technology, not including regeneration, but I'm not an expert and ferroresonance has it's mysteries. Don't have an oscilloscope to do any testing either.

Shared this link before with the caveats of the author affiliation and date.
http://www.contractorsav.com/article/2006/11/07/ac-power

Nothing about the Equitech article implies any kind of panacea. In fact, if it's a ground issue, even separately isolating each amp might not help.

Perhaps Jim or Al can comment on the issue of UL/CSA standards and shunting/grounding as compared to IEC. I gotta step back and listen when those guys are talking.

Sorry, misled again.

UL101 and IEC 60335/60990 are more consistent than I was told. IEC is specific about class and such but generally leakage limited from 0.5mA. Difference is that IEC specifies true RMS reading.

Still, that's per appliance.

... limited TO 0.5mA ...

Somewhere between a decimal place and half a heart attack.

Thanks for the follow-up. Would like to see that more often.