Did you know that legally an Electrical contractor CAN refuse to install something that is NOT UL or ETL listed for it's use? I guess the entire UL or ETL or any other testing labs around the world are a hoax? Kema-Kluer, DIN, and standards industry specs. UL listed doesn't warranty anything ain't gonna have a problem, but it sure does reduce the effects, when there is. CYA.
Indeed. Sadly, this is problematic for even those conscientious manufacturers of audio components who, for economic reasons, can't afford ETL certification, even if they would pass with no, or minimal changes. I've a dealer friend that just mentioned his customers (mainly large, built in, home theater installs) often won't buy non-ETL certified components.
Similarly, many of the mainstream surge protector vendor's [Triplite, etc...] 'Protection Guarantees' are null and void if ANY of the connected components lack ETL certificates.
I believe that every single vendor who has a Circle on Audiocircle, and whose products connect to the mains via anything other than an ETL certified wall wart, is in exactly that same position.
.....
Balanced power ain't for home use. The NEC specifically says NO, it's for commercial, etc, with proper labels and installation. But then, who pays attention to the NEC, what do they know?
Well, any homeowner with a major electrical appliance like a stove, dryer or air conditioner over 15,000BTU should be able to tell you otherwise. I use split phase (balanced) power all the time at home, its just that the voltages involved, North American 240vac (2 antiphase 120vac lines, which us old folks called 'House Power') are far more lethal, about 4 times more so, than the technical, balanced 120vac under discussion. And because a short ACCROSS both lines is far less likely than a single short, balanced power (split phase) is actually substantially safer than single phase mains, for equivalent net voltage swing.
How can this be????? Well..... the manufacturers of 240vac residential appliances go to the incredible effort of fusing and switching BOTH lines and ensuring creepage and leakage values are met for both lines.
or as Frank said -
Correct me if I am wrong, but this "balanced line" signal conditioner appears to put 60V AC on both the hot and ground side of the AC into the preamp.
This is unsafe, because it defeats the built in fuse protection in the preamp. 
The preamp is designed to modern standards with a polarized AC power plug putting the internal fuse first, ahead of everything else on the hot side of the AC line, followed by the switch, transformer, and back to ground. If any internal failure to ground occurs in the preamp, the fuse blows, protecting the user.
With the hairbrained scheme that it appears the balanced line conditioner represents, there would still be 60V AC live in the preamp even after a fuse failure.
How many kids need to be electrocuted for the sake of supposedly "better sound"? 
Geeze 
Frank Van Alstine
Indeed, think of the kids.
Just think of the poor, poor baby childs that could be saved from ineptitude of their delusional parents if only one were to say - ' Ummmm, don't do that unless you up(down, side)grade the component to double pole fusing and switching.'
I'm certainly not criticizing any vendor for not double fusing and switching, after all, without "is designed to modern standards" anymore so than I fault most all vendors for having (IMO) inadequate internal (where it belongs) power conditioning.
And even that is moot if one were to actually follow the NEC requirement that technical power be provided via a GFCI. Fuses protect equipment far better than they protect people. Fault interrupters really do save lives as evidenced by the drastic lowering of incidents involving line connected vibrators and bathtubs. aa, in new construction requiring GFCIs in bathrooms.
The perceived audible improvement is probably another , I know it's balanced now, yup, it sounds much better.....
Yes, it could be hysterical delusions, or alternatively it could be a subjective effect of the clearly measureable parameters such as net reactive leakage currents and transverse mode noise attenuation, Balancing power transformers have strong measureable advantages over straight isolation transformers whether their output is isolated (floating) or neutral bonded. Personally, I've given up on all transformer based conditioners as they're too big and expensive, but don't underestimate their efficacy. (Which is understandable if conclusions are based on non empirical methods.) Nor does a specific powerconditioning topology guarantee excellence, the Transcendence conditioner being rather mediocre, due to its lack of capacitively shunting shield between primary and secondary. But depending on the quality of the mains power, within its current constraints, it is capable of delivering substantial improvements. The already built, less expensive, cmc based PSAudio Duet is IMO preferable to the Transcendence balancing conditioner.
