Isolation Transformers

When did they start printing ’hospital grade’ on anything that was? dang, has it really changed that much since I was in the field? OP did say older isolation transformer?

I guess things have: Hospital grade receptacles include the same markings that appear on general use receptacles, and also include “Hospital Grade” or “Hosp. Grade”, typically on the back of the receptacle where visible during installation

Wasn’t always so. I guess code revisions took a big friggin change to assure no mistake. Guess they factored in no one pays attention to the spec sheets any longer. ..hmph
Reminds me of those on the job concentrating solely on their electrical prints and were clueless to look at the architectural and others...*laffs

In Australia 230v to 230v isolation transformers I have use them on my source gear since the 80’s. they provide "Galvanic Isolation" from the mains and block/filter any dc on the mains.

For the US
http://www.surplussales.com/item/_tp/91092-12.html
https://www.bkprecision.com/products/power-supplies/1604A-single-output-isolation-transformer.html

Cheers George

oicu812

41 posts
04-10-2019 6:34pm

When did they start printing ’hospital grade’ on anything that was? dang, has it really changed that much since I was in the field? OP did say older isolation transformer?

@ oicu812

Medical grade.
Example of:   
https://www.tripplite.com/isolator-series-120v-1000w-ul60601-1-medical-grade-isolation-transformer-4....

As others have said, isolation transformers don't regulate, and they don't even really isolate, except in the sense of from DC. It helps to understand how they work in the first place. That alone will answer a lot of questions. Do a search.

Sounds like the one you're using is pretty close to 1:1. Getting a few volts more out than in tells you the windings aren't equal, its not a perfect 1:1 but again, read up and learn how they work.

The one I use is audiophile grade 2:1 step down, the supposed advantage being you can run 240v to the transformer and get 120v out the other end. Which is what I do, and it is better than the exact same wire and connections that were running 120v before.

Of course if you listen to half the guys around here I am long since dead and buried, along with the half the neighborhood I burned down, voiding warranties, experimenting with lethal blah blah blah yada yada.

As if any of this matters. Because it don't. What matters, the only pro's and con's as you put it, is what you heard. If you didn't hear any improvement then sorry, waste of money. If you did, well then you can tell by how much it was worth it. Them's the pro's. All the rest is a con.

I have used isolation transformers in a variety of settings. One, an old 240/120 step down made by Richard Gray for a big home theatre system- the system itself is long gone- was the only thing that would fully isolate a nasty electrical snap from the air compressor motor that energizes one of my tone arms. I now have a better electrical set up and a dedicated line wired to the regular house main electrical system set up for 20 amps for the air compressor. I use one of those Tripplite 1800 watt jobs. In speaking with the tech at Tripplite before I bought it, the secondary is bonded, it is not really floating. There’s at least one reference to this that I saw on the web, so I am not sure their claim of ’medical grade’ is fully accurate, at least insofar as a floating ground on the secondary.
Even though that dedicated line is separate from the sub-system I use for my audio, I added the iso-transformer just to be sure I didn’t get any noise from the compressor motor-- 1/2 HP, pumps about 130 psi (I use around 65 psi for the arm).
My main system has a 10kVA isolation transformer made by Controlled Power in Michigan, installed in a weather proof case- it weighs about 400 lbs, and has surge protection and some EMI shielding. I listened to the system through ’dirty’ power with the new dedicated wiring while awaiting the arrival of this transformer (they are built to order). Frankly, the ’dirty power’ here is way less noisy than my power in New York. Not surprising, but in NY, I was up along the Hudson in a very small village, no industrial stuff. Here, I am in the middle of Austin, several multi-unit apartment buildings nearby and lots of commercial stuff 3 blocks away. Maybe unnecessary, but the system, which uses very high efficiency horns (104db) will reveal all kinds of nasties. System is dead quiet and the transformer does give me a little peace of mind. (It is grounded back to the main household ground which is an Ufer type ground set up).
The Controlled Power is an old school EI- throws off all kinds of nasties, but since it is outside, I don’t care. The small ones, that use toroidals, can hum and buzz and you don’t want them near your listening environment, although I think they throw off less electrical junk. See http://www.soundstagenetwork.com/maxdb/maxdb071998.htm
That said, there are good toroidal types. Torus is very well regarded. I had a big Equi-Tech wall cabinet that I never put into use; those were the cat’s meow at one point and I believe the transformers came from Torus, who does sell them naked, or through a brand that is plug and play with a case and outlets, ready to go.
A good tool in the arsenal in my estimation, but not a cure-all for all ills.