Step Down Transformer

A good, properly sized one improves sonics IMO. There have been many on both sides of this fence, partly due to improper selection and installation, partly due to transformer's finicky nature. For this application, you should be looking at Signal's multitap (SU/DU) units and read through

http://www.geocities.com/jonrisch/catch2.htm.

http://www.signaltransformer.com/

These type aren't enclosed and will require some DIY. If you're talking about the new Luxmans (NICE!), they are going to need a big tranny, in the 2-3 KVA range, possibly more if balanced. The general rule is double to triple the maximum power consumption of the amps, including derating if balanced. You might have better luck if you can feed them 240V.

Do NOT buy a "voltage converter" for an audio application! There is a reason they're inexpensive.

The 50/60 Hz thing should not be an issue on an amp this quality. Japan has both standards in various parts of the country.

Ngjockey, Thanks for Info. but something I don't understand.
There was a many forums about step down transformers and
main concerns are Amplifier sonics. Why would Amplifier
perform sonically different. An Amplifier is feed with 100V,
frequency is 50/60Hz so I don't see any problems. It should
perform without any distortion. Luxman's power consumption
is 240W so I would go with 2000W transformer.
I would really appreciate your opinion since you are familiar
with the issue.
Regards

Since you asked

1) A transformer is a filter. Anything that is not an AC wave on the primary side is reduced on the secondary. Noise reduction can be up to 20 dB but , more often, between 6 to 12. Common mode noise rejection is typically 120dB and normal mode is 60 dB for an EI-type transformer. Toroidal transformers are more closely coupled and translate more noise. Voltage spike reduction by a factor of 8:1 is fairly typical. There do not reduce harmonics, by themselves, without some trickery. In fact, they are more efficient at 400 Hz. Power transformers are not wideband audio transformers.

2) A transformer can saturate for a number of reasons besides being overloaded. As little as a 10 mV DC offset on the line will compromise any transformer causing mechanical hum and severely reduced capacity. Ironically, the same DC is completely eliminated on the secondary side.

3) The electrical load (amplifier in this case) is dynamic and reactive, meaning it does not take a steady current and doesn't leave one either. High speed digital circuits can create a lot of noise, in which case an iso reduces noise from going back into the AC line. Capacitors charge and discharge in spikes. Diodes, rectifiers ...yada,yada. That is one reason for oversizing an xformer and in some cases even exceeding the 15A capacity of the house circuit. Look inside a Pass XA160, for a blatant example, and you'll see a 3KVA toroid for a 550W class A steady draw.

4) The xformer, itself, is an inductive and capacitive load. Normal efficiency is about 90 - 92% but the "exciting" current (into no load) is often 10 -15 % of the maximum rating. Powering up an xformer is a lot like starting an electric motor and can draw several times it's normal current momentarily.

5) There is no reason why an adequately designed and sized xformer would slow down reactions or cause dynamic compression. The power had to go through several transformers before it reached your house. Underestimating and using smaller, less expensive units is the main problem.

6) Question: Does reducing noise and distortion sound less dynamic?

7) Isolation and step-down transformers are much more common and integrated than most people realize in hospital/laboratory, industrial and commercial systems.

There is much more that I don't know about transformers than I do know and the more I learn, the more I realize my ignorance. They are completely predictable only in hindsight and a unique art and science.

NGJockey -- Excellent and very informative post. Thanks!

Regards,
-- Al