If you live in one part of the world, but buy an amplifier from another part of the world, say a Norwegian (230V) buying from the USA (110V), you need to transform the voltage. There are probably good and bad ways of doing this, and good (“audiophile”) transformers and bad (noisy) transformers. Or perhaps it’s possible to just dig into the amp you just bought and tinker.
What are the best solutions? Or: What are the best transformers for such tasks?
Now, I am only going on what I am told here, not what I know as I am not an electrical engineer…
I discussed this in the past with a couple of electrical engineers we have on our team and their answer was that AC to AC transformers don’t introduce noise, or at least, not to the point where it matters. AC to DC transformers are the ones that create noise.
They went into a lot of detail but basically they said that the power you receive already goes through many transformers that reduce the voltage on its way from the electrical station to you home/work/whatever. Tens of thousands of of volts are reduced along the way until it is the final 220V (or 110V) and because the it is still AC, the wave forms stay the same.
They say that having a simple AC to DC transformers plugged in somewhere on your circuit at home will introduce more noise than any of the AC to AC transformers, unless the AC to AC transformer has an issue.
Again, this is only what I am told so do not take this as fact without research.
Thank you, SenyorC, that makes sense. I had a (self made) dimmer switch for the lights once, and I had to choose between dimmed lights and playing music. That thing made a LOT of noise! But I can see transformers would be reasonably harmless, and the assurances of that from your team are gold. Thank you! 
Toroidal tranformer now ordered (long ago, but not yet delivered), but I decided to read up a litte, and it seems that if there is DC in the mains, then something called an IE transformer might be better. For those of us who have ears that “can hear the grass grow” and just want perfection, of course.
I now have an Airlink toroidal transformer in the house, transforming from 100V (Japan), aaaand …
I put the power into a Luxman P750u mark ii (not sold outside of Japan as of yet). And the result is: If I put on my Grado RS-1 in the jack out, and turn on High Gain and Max Volume, AND I press the Grados to my ears, I hear a slight buzzing noise (20dB or so). This probably stems from the transformer. The sensitivity of the Grado RS1 headphones is 111.33 dB/V SPL by the voltage and 96.63 dB/mW SPL by the power. The Luxman puts out 1W per channel at 32Ω. So if I don’t misunderstand the issue of sensitivity, this means that the sound is well below the audible threshold for not just my ears but anyone’s when music is played. The sound is totally absent on the 1266, btw, at least to my ears.
I have a little bit of EE knowledge, so I will see if I can explain is a little.
Few quick quick notes:
So why are audio transformers so expensive? There is two things:
I also want to address some thing @Solan mentioned about DC on the mains. This is completely true, and is accounted for in all amp designs. You know how I mentioned that transformers work through magnetic flux? I know this may sound confusing, but constant DC in a circuit will produce no magnetic flux. So, essentially any transformer in a circuit will act as a DC filter.
Hey,
I would also like to buy the Luxman P-750U and unfortunately these are only for sale in Japan.
And since I live in Belgium, a conversion from 220V to 100 V is necessary.
This requires a transformer and apparently you have done this too.
What would I need for this and what is the influence on the music in terms of interference.
Thanks in advance for the reaction.
Frank.
I bought a transformer from Airlink, a British company. The Luxman, I bought in Japan. Many vendors (most, actually) only sell inside Japan, so I used Buyee to buy for me and then ship. The fee that Buyee charged was less than the difference between the FedEx charge from vendors who did sell outside Japan, and the discounted FedEx charge Buyee have negotiated for themselves. And yet it was fast. (Damn, now I feel I’ve earned myself a commission from Buyee … )
Hey, Al thanks for the info and I’ve already used it to search the internet for info.
I was not familiar with the Buyee site, but can it be trusted?
And I have seen on ebay that there are several for sale, different sellers but the same photo, I find it strange.
What type of airlink did you just buy?
Frank.
Buyee is rather large, and my experience with them was 100% positive. That is only 1 data point, since I made only 1 purchase through them, but I would have no trouble doing so again. As for the multiple photos, I noticed that the same photos are recycled by many. Notice that Japan has many other sites than eBay, most notably Rakuten. And there Buyee is useful again, since they are also a portal to these biggest sites.
Airlink: I bought two. One simple voltage transformer with 2 outputs, and one transformer to “purify” the electricity and keep my electronics safe in case of power surges etc. I set the output at 220V instead of 230V since I have an old-fashioned valve amp that is happiest at 220.
Hey, I sent an email for more info about the transformers but haven’t received an answer yet, maybe next week.
And do you notice something about the transformer, poorer quality or interference while listening.
There is a slight hum from the transformer itself. Audible hum from the box, not hum that propagates up the chain to the amp etc. That said, all transformers in my house give off a low hum. Very low, so no bother. But if you are averse to humming at any volume, a switching style box may be more what you want. I personally don’t like the switching style power supplies, and avoid them if I can.
We have decided not to buy in Japan after all.
Bought a Mytek brooklin, is not the same as a Luxman.
But it can serve.