Great experimenting! In my first old apartment in Chicago that had steam heat I couldn’t even listen to my music through the electrical grid hiss or watch my projector because of the pulsing image. It was at that point I realized how important clean power is. As I upgraded and bought equipment I listened to manufacturer fears of starving my system and plugged all my amps directly into the wall with critical items on a power conditioner with surge protection. Well I just moved and the power grid in my new place is a mess. We have brownouts and power surges all the time and lightening actually hit my equipment through the coax cable of the TV and took out the cable box, video processor, and projector. Back to research a protective solution that won’t affect the sound and can support all my equipment and I discovered the PS Audio power regeneration products and bought a P15. What a difference in sound quality! It has oodles of power, dead quite background, outputs a perfect sine wave to the equipment regulating any spikes or sags in the incoming power, soft starts all the equipment in the order I want as well as shut down order (huge WAF convenience factor, not to be underestimated). I bought it for the protection and got many other benefits. There are a lot of solid products and solutions out there but count me as a fan of power regeneration. One plug is less attractive to lightening as there isn’t a path out of the system, also when I see storms coming in it gets pulled and there is zero chance of lightening damage! FYI the Weatherbug App shows local lightening strikes by distance in real time. Oh and I moved to streaming my cable through Direct TV NOW (there are a number of services) to literally cut the cord and isolate the system.
My wife’s car was actually down the street at the stoplight and the pole was hit by lightening (same storm that hit my stuff). The EMP stopped the car in its tracks. It wouldn’t start for a few minutes and then fired right up and she was on her way. Granted her ears were ringing and seeing spots for awhile. Car is still running. . . We shall see. Brown outs and surges will kill your equipment as well just death by a thousand cuts. . .
spatialking A good post. Power gremlins are sneaky pests. I have always upgraded from the simple one ground rod to multiple ground rods...where I can. I like the idea of independent ground fields. Power protection can be difficult even with good power supply equipment. My APC would sonically cloud the listening environment under different conditions. To give credit where it is due, I am very satisfied with my PS Audio DirectStream Power Plant 15. Power problems have completely disappeared with every device using this unit.
The car is a Kia Sorento. We only have 50k miles on it so hoping not too much damage was done. I was able to fix my Lumagen video processor as I saw that the damage from the lightning burned a trace on the output board and the sound still worked on the other output. So I took a chance and bought an upgraded 18Gz output board and plugged it in and it has been working great. The projector’s main input (with HDR) was toasted but input one is working so I’ve used an Integral to fool input one to think it’s getting an HDMI 1.8 signal but sending an18Gz HDR signal through it and the projector is reading and displaying HDR. Just like the car, fingers crossed. . . I need all this stuff to keep working. My daughter’s loans I co-signed for are starting up as she is graduating and I couldn’t afford to replace any of it for a long time. Lol
First let me first disclose I design cables, including power cables on a profession level.
Back in the last century I designed military gen sets. I can confirm this post from similar test then and in recent history testing. In the last round of testing I found that the cleaner the power going into power supply the better the performance of the product (stereo, computer, projector,...). If you take the advice (I believe it to be good), don't forget the cabling from the re-generator to the equipment. The broader the spectrum of attenuation, the lower the noise floor. Low frequency emission in the EMI ranges can and will contaminate a system, in other words the music you are playing can and will interfere with its own quality.
What an interesting post. It's so nice to hear from a professional in the power distribution field who as an audiophile, understands the principals of "clean" power, but more importantly its effect and importance to our hobby.
While I found the specifications listed informative, it left me wondering what ready-made and marketed equipment may met them. Would simply searching for the noted specifications garner some for sale devices?
Spatialking, if you've found some professional (non-audiophile) or audiophile related hardware that you have used and recommend, advising same would be very helpful and appreciated.
I've often surmised that non-audiophile based clean power devices must be available that would work as well or better than many audiophile based ones. For example, hardware for scientific, medical, or laboratory purposes. However, I wouldn't know what to look for, or whether it would be satisfactory, too costly, etc.
Oftentimes equipment specifically marketed to audiophiles is more expensive than other equally satisfactory items. Using a Magic Eraser as a stylus cleaner quickly comes to mind. The use of hospital grade receptacles must have transitioned into audiophile grade ones. I know some audiophile receptacles are still based on them. How about clean power devices? What may perform exceedingly well for a modest cost -- power cleaners, regenerators, cables, etc....? Or what may perform better than most audiophile grade components, but cost similarly/less, or at least NOT require a second mortgage to afford (grin)?
+1 @mrmb -- great post @spatialking and left me wanting to at least do something to mitigate electrical issues I almost certainly have here. Could you possibly post some links to some products to help us non-EE types try to fight this battle? I've not a clue what to buy or even ask for. Thanks again for a great post!
I use a Furman REF20 power conditioner (basically a big toroid transformer with some cleaning gizmos, big stiffening Cap, and partial balanced output)Also a PS Audio P-600 regenerator. Throw in fancy wires, powercords, PS Audio Noise Harvesters and $3700 worth of Furutech AC Duplex and you know what I use to clear up my AC.
@elizabeth, I too use some of what you do. But as we in this hobby are wont to do, I'm always wondering if there is something better. Especially something better at a budget beating cost.
Having someone with @spatialking professional background and scientific experience on this board is a real plus. He has anecdotal experiences and knowledge which are the reasons why most of us are here. But unlike many of us, his experiences are couched in his professional training; which I find a big plus when wading through these fields of opinions while looking for the wheat through ALL of the chaff.
This is also the reason why I appreciate the opinions of manufacturers in these pages. While I know they're more specifically biased than the rest of us, their experiences and training provide insights that I find fascinating and very valuable.
Hopefully @spatialking will continue to post his experiences and discoveries and may make more specific product suggestions or at the very least, subtly point to a direction [and product(s)] that is more readily apparent.
The Furman Ref20 is a great piece of kit.
As the OP mentioned, very high frequencies can go right through a transformer, while the transformer tends to filter out very low frequency noise (100s to low 10kHz)
However, the Furman includes SMP filtering, a nearly ideal surge supressor plus noise filter that starts at 3 kHz. That's well below the OP's suggested targets.
The earth ground is for lightning. It carries no current. The ground must return to neutral in split 120v systems or the system MAY BE LETHAL.
PLEASE see https://centralindianaaes.files.wordpress.com/2012/09/indy-aes-2012-seminar-w-notes-v1-0.pdf before futzing.
Note test of A/C wiring in steel conduit produces the WORST noise performance. See p33ff.
Hospital / audiophile grade receptacles lift the safety ground from the mount ground and only have effect in building wired with metal conduit.
Installations wired with Romex surpass steel and are only surpassed by twisted LNE in aluminum and twisted LN.
@erik_squires Would series mode suppressors further complement my Equitech 2Q balanced power transformer? I do use Sound Application and MIT Cables power conditioning cables/units to excellent effect. My experience has been that there’s always a benefit by maximizing elimination of ac noise. (I wish I could get technical details on these products.)
@ptss - I cannot tell you if you will hear a difference, but in my mind there’s very few technologies in audio power conditioning well documented:
Everything else is just some form of shunt noise reduction, which is almost never documented.
The series mode protection is also licened by PS Audio if not others. I consider it the minimum due to:
@mrmb, @soix - Here are some ideas for noise suppression. There are a number of quality noise suppression devices out there. Furman is a good brand, so is PS Audio and Tripplite, but do check out the specs. Here are the specs for a Furman M-8X2, a basic power distribution and noise suppression, and priced at $80.
· Standard Level AC Surge Protection: Merit Class (sacrificial)
· Noise Attenuation: Transverse mode: >23dB, 200 kHz to 10MHz
So let’s explain what this means. Sacrificial means when a lightening pulse hits the device will short the input power forcing a fuse or circuit breaker to blow and opening the circuit.
Essentially, the unit will have to be replaced; the philosophy is it’s better to replace something inexpensive than expensive stuff downstream. This is how I designed the LEMP filter, I had all the noise filtering up front and following by sacrificial electronics. It is good of Furman to specify this, since you know what you are getting. The other philosophy is non-sacrificial, that is a design that has aggressive filtering and stores the energy in a reactive space, thus dissipating the energy more slowly. A good example of this is here: https://zerosurge.com/wp-content/uploads/2018/04/2R-Series-0418.pdf and here: https://zerosurge.com/
There is no reason you can’t combine the two philosophies. J Put the heavy filtering up front, followed by spike suppression.
Spike Protection Mode means the protection is from Line to Neutral and there is no protection from neutral to ground. This is a reasonable concept since neutral is tied to ground at the main panel. There are other arguments against this, stating neutral should be spike protected to ground. However, the more protection one adds, the more the cost goes up. At some point, has you have to evaluate bang for buck. Personally, I put in neutral to ground protection, both as spike and as filtering but then I wasn’t trying to hit a price point.
Joules is the unit to measure energy, equals the work done when a current of one ampere passes through a resistance of one ohm for one second, which is one Watt. Joule units define the energy dissipated by the device; the more the better. 150 Joules here is not much, 3000 Joules is getting somewhere, 6000 Joules or more is healthy. Expect to pay a lot more as these numbers go up.
Peak Impulse Current is the maximum spike current that the surge protection circuit can handle to protect downstream electronics. Again, 12,000 Amps is a starting point, I put in 44,000 Amperes and there are bigger devices out there than what I used. That LEMP filter I designed for the energy system had 300,000 Amps of Peak Current.
The 8/20 microsecond waveform is a standard IEEE test waveform for lightening spikes where the maximum voltage is reached in 8 microseconds and decreases to 50% in 20 microseconds. Therefore, the higher the voltage pulse the narrower the pulse becomes. There are other IEEE standard pulses but this is the most commonly used one.
Let Through Voltage is an important spec. It tells you the amount of voltage that the protection circuit will allow to pass through before the circuit begins to attenuate the spike. Here it is say it will allow a 400V pulse at 125 Amps. Understand there is always a Let Through Voltage, keeping it tame is a tough call and an engineering compromise. Reduce the Let Through Voltage and the pulse circuit works a lot more, heats up, and is in a weakened state when the big spike comes along. Relax the design and the pulse circuit is more able to handle a big pulse but allows more energy through when it does happen. The only good solution here is a good design.
Everything I wrote about so far is about spike suppression, which is lightening and spike noise from motors, air conditioners, etc. This has nothing to do with EMI and RF noise, which is more problematic for sound quality. The spec 200 KHz to 10 MHz is the bandwidth where the EMI filter works and produces at least 23 dB of suppression. In my first posting, I stated look for something that has at least 30 dB of suppression from 100K to 20 MHz, so this unit is a bit on the shy side of what I suggested. Forty dB is much better and it is unlikely you will find anything above 60 dB.
So, is this bad? It costs $80 and for that price, the protection is quite fair. If you have the budget, definitely look for more EMI suppression. If you live in areas where high winds are common, earthquakes, or massive storms, having a lot more spike suppression is a good idea. It is not just lightening that produces massive electrical spikes. A storm knocking out a power pole can do a real number on your system.
BTW, I am using three extension cords on the right channel 200W Conrad Johnson amp. It is really a kludge setup but far better than using that other outlet. If I use the wall receptacle next to it I get a lot hum for reasons I have yet to determine. The fix this weekend is to replace the extension cords with a single 8 AWG cord 25 feet long.
If I use the wall receptacle next to it I get a lot hum for reasons I have yet to determine.Likely different circuit and a ground loop.
Stick with plain, old school incandescent bulbsHaven't a problem with a dimmer since the '70s. I use two LED torchier lamps on dimmers and there is ZERO difference in the noise spectrum when viewed on a 'scope. Of course they are not on the same circuit as the HiFi.
I don't want to get into a situation where I am reviewing equipment but I will try to answer all your questions.
Here is the PS Audio device: https://www.psaudio.com/dectet-power-center/ There are no specifications given so I have no idea how much attenuation it provides, what frequency range it attenuates, or anything like that. The parts in the photo do look appropriate, though.
The Furman IT-REF 15l and 20l do have excellent specifications throughout the bandwidth that needs filtering. If you have the budget, these look very promising. Certainly I would feel confident plugging one into my system given the published specifications and the fact it was tested by an independent testing lab. Amazon has the 15l for $2500 and $4000 for the 20l. As I said before, if you want to get serious about EMI it also gets expensive.
The Equitech also looks very good: https://www.equitech.com/productsold/son-of-q-shelf-or-rack-mounted-chassis-systems-2/ All torridal transformers provide good high frequency isolation since it doesn't have interwinding parasitic capacitance that are inherent with the typical E style transformers. I found it online at $2640. The Equitech didn't say much about filtering and surge protection, it has it but I don't know what it has or how effective it is.
The thing to understand here is there is no one perfect product, if one addresses the problem, most EMI problems will fade. I doubt you would go wrong with any of these but do understand you get what you pay for. So, don't expect a $200 power strip to equal these EMI dreadnoughts! Given what I have seen here, I'd say buy one of these and forget about EMI issues.
Case in point - a number of years back I was working for a very large, well known test equipment company, of which I am sure everyone knows the name. We were pushing the bandwidth limits a standard FR4 controlled impedance PCBA could manage, so we made a test board with exactly a 50 Ohm line, a line with 10% error, a line with 30% error, a line with 50% error, and a line with no controlled impedance whatsoever. What we found was even the 50% error line had reasonable performance while the one with no control was not usable. If you address the problem, even with error, you are far ahead of the game than ignoring it.
One of the nice benefits from these units is they monitor the line and shut down during long term brownouts or over voltage conditions. The utility companies have specifications on this sort of thing, call "ride through" where the user equipment can ride through the brownout or surge without self destructing. Back when I worked in audio, I knew a few audio companies tested their products for this but I doubt the majority do. The idea is products have a given ride through while the utility companies work to prevent problems that exceed the general ride through spec.
I didn't look at the regenerative products such as the big ones from PS Audio. These are an entirely different animal since your system is now powered from the power supply / amplifier / inverter contained within. The grid becomes secondary and not really in the picture. Unless you have horrible line regulation, you probably don't need to go to this extreme.
One thing is for sure, I would definitely spend $400 or $500 on EMI filtering and surge protection before I would spend $400 or $500 on spiffy line cords. Ignoring the awesome cosmetic improvements they provide, this equipment is very real and very effective. On the other hand, if you want really spiffy and sexy looking power distribution after you buy one of these ..... :-)
..a couple of years ago a lightening strike took out one of my Vandersteen amps (right side) in my 5A speakers. The amp was repaired and sent back. I don't know when, but for a couple of years, I've been hearing a noise (resonance sounding at certain frequencies) in my left speaker that appears in the left even after changing speaker cables, - on phono and Cd. When I plugged the amp into a different outlet in the same room the sound gets much better, but the resonance remains in the left speaker. I took the tweeter and mid out and sent them to Vandersteen who declared them "fine" I sent them the bass amp, and the crossover and they came back "fine"...the resonance remains. I don't know where to go from here. Any suggestions?
I've had a couple of Zerosurge surge protectors for a long time,. and they helped clean up the power in my house, but in the apt I'm living in now, the RFI is horrendous, and they don't can't do much. I can't listen to my SW receivers here at all, there is buzzing all over the HF spectrum coming from this building and the nursing home next door has a BZZZZZZZZZZZT! Every couple of seconds that is annoying beyond belief. I have my amp and HT running off the ZS boxes now, and checked on a scope, the line is pretty clean, but there is a ton of RF everywhere "in the air". My stuff (midfi at best to most of you here) has no hissing or any kind of background grunge when I listened to it with headphones and the level cranked up to a point if that BZZZZZZZZZZZT! had got through(or anything else), it wouldn't have been pleasant at all. All I heard is the very slight hiss I hear from every amp, etc, cranked up, yes, even the ones people claim are silent as they get. I had a couple of RFI issues on my old HT system that suddenly cured themselves and to this day we don't know how or why, but the hash noise it made when playing CDs on both of my two players at the time suddenly disappeared and never came back.
As far as a near or direct lightning strike goes, I've had both several times. I had an almost new CB and antenna get blasted by a direct hit about 40 years ago in Las Vegas. The fiberglass antenna shattered into about a thousand litle sharp pieces of fiberglass and IC's were vaporized inside the CB. Where they had been was clean, but around each place an IC was, there was scortching and in a couple of places, PC traces were blown off the board or vaporized too. The second direct hit was in Toledo, and it hit the same model of CB antenna, sending pieces over mine and two neighbor's yards. That hit killed a satellite receiver too. The near misses killed a couple of decent quality surge protectors and my newest, best VCRs at the time. When I tried to collect on the "guaranteed" up to $25000 coverage, they laughed at me.
Re the opening post:
I usually find and bring some incandescent bulbs to audio shows for our given display room.
It has to do with the idea of resistive dissipation of transient noise in the lines. Seems like a good premise and seems to work....it also provides a stable load, continuously, on the given line. A line that is getting hammered by the audio gear’s messy demands. A little bit of an incandescent secret weapon. Every little bit helps and adds up. It’s not just the idea of the removal of the noise of CCFL and LED bulbs, it’s a double whammy of that and noise reduction as an added bonus.
Details details details, sweat the details.
You might want to look into Elgar for power conditioning. They can make a very pure sine wave right up to full output (which means no HF noise).
They employ a large isolation transformer equipped with a feedback loop. An on-board low distortion oscillator is synchronized to the AC line. That output is compared to the conditioner's output, and a feedback signal is applied via a power amp to the isolation transformer. The feedback amp can also buck the winding of the transformer, so it can regulate line voltage too.
Their conditioners that use this principle are fairly old so you find them on ebay.
If anybody is serious about a Furman, best deal I have seen for a while on one compared to new prices!
I was at Home Depot last night and I picked up this unit for my home workstation. For $40 it is a very good unit and well worth the cost. https://www.homedepot.com/p/Commercial-Electric-12-Outlet-USB-RJ45-Coax-Surge-Protector-with-6-ft-Co... The webpage doesn't give all the specs, it has RF filters providing 43dB of attenuation from 150KHz to 100MHz. It also meets UL 1449, more on that below. It also has both TVS and TSR protection. All in all, a good unit for the money. I did note they specified 4500 Joules of max energy dissipated as the sum of L-N, L-G, and N-G, but they did clarify this on the back of the box. 3300 Joules from L-N is pretty good; 6600 was the most but that unit was more than twice the money, too. My continual gripe with all these units is the plug layout. To save space (cost) they squish them together so if you have large plugs you can't use all the outlets. Likewise if you have the plug in transformers or wall-wart units.
About UL1449 - UL got a lot more restrictive with leakage currents in this latest revision. In so doing, the "let through voltage" is higher now than it was in the previous version. This unit has a 500V let through voltage, which is the consequence of UL1449. If your equipment has any internal protection, it should handle this easily since it isn't present for long. However, I'd rather have something in my house meeting UL1449 than something that is not. It might self destruct if I get a big enough surge but I am not worried about it bursting into flames.
Update on Equi-Tech: I found a more detailed description online about how it works. Yes, the entire balanced line concept is a well known and well defined power distribution concept. Envision how balanced interconnects work except this is for your grid power.
Do be aware if you spring for this - currently there are no NEMA receptacles or plugs designed for balanced 120VAC power. Balanced 240VAC, yes, there are options but not for 120VAC. This means you can't get a building permit to install it and the NEC and UL/CSA/IEEE governing bodies don't recognize it.
Here in CA, if you install this without a permit and your house burns, even though it is no fault of your own, your homeowners insurance isn't required to pay for the damages. There are other states that have similar laws as well. It pays to investigate. If you can get a permit, you are home free (not to make a pun).
Currently, Equi-Tech is working with Intertek (the same safety company we use for our high energy equipment at work) and the NEC to get this concept approved. I have no idea when that will occur, safety regulation changes take years to happen and I don't know how far along they are. NEMA will also need to get involved since it will require a new plug receptacle format. If you are considering buying one of these, call them and find out where they are in the approval process. Get all the documentation from them and any suggestions on getting a permit to have it installed. Then call your local building permit folks, have a meeting with them, and see if you can get a permit. A permit is required since it doesn't plug into your outlet, rather it ties into your main distribution panel, so a permit is definitely required.
It is a great concept for audiophile power, it's a bummer about NEC. The closest thing in the NEC handbook is called a separately derived system with an isolated ground. That is a good concept and you can get a permit for that but it is not a balanced power distribution network like Equi-Tech.
spatialking OP118 posts12-15-2018 1:31pm
See NEC 647.7 (4) Exception:
Receptacles and attachment plugs rated 125-volt, single phase, 15- or 20-amperes, and that are identified for use with grounded circuit conductors, shall be permitted in machine rooms, control rooms, equipment rooms, equipment racks, and other similar locations that are restricted to use by qualified personnel.Also see 647.7 (4) (B) Isolated Ground Receptacles.
Isolated ground receptacles shall be permitted as described in 250.146(D); however, the branch circuit equipment grounding conductor shall be terminated as required in 647.6(B)
Orange IG receptacles are commonly used for 3 wire 60/120 volt power systems. And of course shall be GFCI protected.
Here’s the corker though. NEC 647.3 (1) and (2)
(1) The system is installed only in commercial or industrial occupancies.It’s not NEC approved to be installed and hardwired in a residential occupancy.
Though the AHJ (Authority Having Jurisdiction) has the final say.
IF a licensed electrician installs and wires it in a dwelling, he/she is not going to try and pull an electrical permit. Very good chance it will be denied.
Either way, I don't see any AHJ issuing a permit for residential use of this equipment. Yes, NEC 647.7(4) allows for use in restricted situations but as you pointed out a residential home does not qualify. Gosh, I wonder if the audiophile owner would even qualify as "qualified personnel" under NEC definitions?
I'd like to see an application where an AHJ signed a permit for the orange hospital ground NEMA 5-15R or NEMA 5-20R receptacle for a balanced 60VAC line. I don't see that happening, especially in the stronger cities such as New York or Los Angeles. (Stronger here meaning a number of AHJ's in the city sit on the UL or IEEE code boards) Neutral has to be tied to earth, not to the end of 60VAC transformer leg. Granted, maybe most equipment can deal with 60VAC on the neutral leg but I'd never want to bet my money all equipment is okay with it.
An AHJ might buy off on NEC 647.7(4) for a 60 VAC single ended 60VAC line using the NEMA 5-15R or -20R receptacle in a restricted area but I sure don't see it happening for a 60VAC transformer leg on the neutral line. However, that being said, they might indeed sign off on it if the equipment was hardwired, though. That is surely a thought to ponder.
If you know of a installation that had a permit signed off for a Balanced 60VAC line using a Hospital Grade NEMA 5-15R or -20R receptacle, I sure like to hear about it.
Either way, I don’t see any AHJ issuing a permit for residential use of this equipment.Agree.
If you read NEC Article 647 it clearly states 60/120V power systems are approved for use in commercial and industrial occupancies. Period..... NEC 647.3 General.
Years ago I worked with a member that was building a separate building structure on his property for his audio system. He wanted to feed his audio equipment from a 60/120V power system. I said he might try having his electrical contractor, when applying for the electrical permit, to specify the building will be used as a recording studio. Doing so the occupancy would be classified commercial. I said it also would depend on the zoning of the property. Some cities prohibit even light commercial, there in, a business in a residential area. It will all come down to the AHJ in his area. As memory serves me the permit was approved.
I’d like to see an application where an AHJ signed a permit for the orange hospital ground NEMA 5-15R or NEMA 5-20R receptacle for a balanced 60VAC line.Not a problem if NEC 647.3 is met as well as the rest of 647 that applies.
Neutral has to be tied to earth, not to the end of 60VAC transformer leg. Granted, maybe most equipment can deal with 60VAC on the neutral leg but I’d never want to bet my money all equipment is okay with it.The center tap, neutral, of a 60/120V transformer is tied to earth. The branch circuit equipment grounding conductor is connected, bonded, to transformer neutral as well. Not any different than the secondary of a single phase 120/240V transformer. The two hot (ungrounded) legs of the 60/120V power system will feed the receptacle.
Granted, maybe most equipment can deal with 60VAC on the neutral leg but I’d never want to bet my money all equipment is okay with it.The audio equipment only sees 120Vac.
An AHJ might buy off on NEC 647.7(4) for a 60 VAC single ended 60VAC line using the NEMA 5-15R or -20R receptacle in a restricted area but I sure don’t see it happening for a 60VAC transformer leg on the neutral line. However, that being said, they might indeed sign off on it if the equipment was hardwired, though. That is surely a thought to ponder.If you read NEC 647 hard wired receptacles fed from a 60/120Vac power system can only be installed in locations specified in Article 647. They also must meet 647.3 (2). "The system’s use is restricted to areas under close supervision by qualified personnel."
Equi-tech knows that. But they still skirt NEC Article 647 and sell to the general public.
Big bold letters.
Commercial and Industrial Products
(For Permanent Building Wiring and Temporary / Mobile Power)
So why in big bold letters? Might have something to do the Listing of the equipment and to cover their butt from a lawsuit.
I had a full Equitech balanced installation in my home in Los Angeles and had no problems getting the permit signed off. The only requirement was that the balanced receptacles were all labeled “technical power only”
the real problem came in selling the house when the setup freaked out the buyer and I had to de-install the Equitech transformer in a hurry and replace it with a normal sub panel!
and listen to this from the man who ought to know a thing or two about audio system power. I'm not pushing the product but to me the information is invaluable.