balanced power supplies: group purchase of iso...?

Power in my apartment is abysmal, and I've tried a number of things to remove grunge from the AC line: LC filter, PSAudio HC outlet, and now a giant 2 KVA isolation transformer.

The iso transformer, a Plitron model, produces balanced AC, and does seem to clean the line quite a bit. I installed it in a rather nice box with a big Classe-style aluminum faceplate and Schurter and Hubble components. I don't know *exactly* what effect it has on the power signal; my next project will be buying or borrowing an old o-scope or a power quality meter on ebay and seeing precisely what each device -- the LC filter, the PSAudio, and the balanced power supply -- does to the AC signal. An obvious and galling problem that remains, though, is that the transformer buzzes.

Toroidal transformers are known for being more efficient than traditional EI transformers, but they're also more sensitive to dirty power than the EIs. A toroid will buzz and complain in conditions of excessive noise, overvoltage, and DC offset. I suspect now, having (hopefully) corrected the problem of noise entering the tranny, that the cause of the buzzing is either DC offset or overvoltage, or both.

Plitron can build, for a price, transformers with "LoNo" technology -- trannys which would be far less susceptible to noise from DC offset. And a custom design could be impemented that would allow for overvoltage. The problem with a new custom design is, of course, cost.

Would anyone be interested in a group purchase of custom-designed toroid isolation transformers? They'd be designed specifically to handle gracefully the major problems found on modern AC lines, and would produce clean balanced output. I haven't yet submitted specs to an engineer at Plitron, but if there's enough interest, we could agree on specs and then place a order of modest volume.
I've been playing with power for some time now. First, I tried off-the-shelf products (RGPC, Equi=tech, etc) then I realized that I am paying for someone else's experiments and started doing most myself. Last few transformers that were custom-built for me were so inexpensive that I would not even bother group order them. Plitron is a good company but I am not sure their prices are the best possible.

Thanks, Alex. I'm in that boat now, experimenting with various ways to clean power. If peope realized how easy it is to stick a big transformer in a box and connect it to power in and to an outlet or two, BPT would be out of business, or at least compelled to drop prices a bit. Have you settled on one or more devices or methods that seem to work well? Have you found an inexpensive way to measure "works well", a more quantitative method than listening tests?

What company or companies were willing to custom-build a transformer to your spec and not charge a fortune for a one-off design?

I am not done yet with my experiments. It takes time to put it together, do some measurements and listen to actual changes, which sometimes are not immediately noticeable. Besides, with AC season one day can be very different from another.
Looks like I will have at least three PLCs - for digital, amplifier and TT. My digital rig definitely "likes" balanced (-60,0,+60) while amplifier for some weird reason works best with simple isolation transformer.
With TT I am still undecided.
There are several companies that I used, so far in my opinion Amveco seems to be a better one.

Alex, if I may pose a question for you: how would you go about reducing overvoltage and DC offset? I'm assuming that since the PS Audio device and the JR filter should perform low-pass filtering, relatively clean AC is arriving at the external side of my iso transformer.
I paid a ridiculous amount for a bridge rectifier in a box -- the Ah! DC Offset Killer -- that should have eliminated transformer buzzing, but merely reduced it a smidge. I've measured 60Hz output from my balanced transformer at +62/-62 V, so the buzzing might also or instead be an overvoltage condition. Each rectifier should produce a 1.4 V drop (0.7 x 2), yes?

Well built tranformer should be able to take some DC without buzzing.
When you start working with high quality "old school" ultra-isolation transformers, you'll soon realize that most any toroid is a joke. They are used strictly for cost cutting and weight reduction reasons, not for performance. If you can avoid them, do so.

While not directly related to this subject, you might want to take a look at this thread over on AA regarding the selection of transformers. Sean

Good to see you back.

You just couldn't resist--what a 1200 modder can cause!