The EIA "33/66" is quite different from IEC standard or EIA RS-490 original standard, but "variations" of the EIA standard are beeing used by many other brands around the world, specially digital amplifiers.

Why Studio R uses other standards instead of EIA "33/66" and what are the differences between then?
Studio R uses the a version of the tradicional IEC standards because we think they are more familiar and useful for the customer. The IEC is a official standard used by many traditional amplifier makers around the world for a longer time.
The great and important difference between the IEC standard version we use and EIA "33/66", is the power measuring method. The EIA "33/66" demands that the amplifier sustain the maximum rated power only for 33 mili-seconds, followed by a rest interval of 66 mili-seconds (using a 1kHz burst signal (33,3ms ON / 66,6ms OFF). A standard continuous tests signal (like the one used by the IEC standard) will possibly activate protection systems which limits the amplifier's max.-output voltage.
The Studio R amplifiers have the advantage of being able to sustain the maximun rated power output for more than 500 mili-seconds with continuous test signals, with no power limiting. It provides a better sound quality specially in low-frequencies and makes the amplifier capable of accurately reproducing any musical signal and then use external digital processing to create compression, distortion, or other effects that are needed.

For more information about amplifier's real power sustaining capabilities and its importance, refer to Mr. John Meyer's article (from Meyer Sound* USA): http://www.meyersound.com/support/papers/amp_power.htm

So, while measured using EIA "33/66" methods, our amplifiers can achieve significantly higher power ratings than any other..