Found this on Audioholics in an ariticle on amplifier claimes. Their math looks correct to me.

"How can my amp claim 200wpc / 400wpc x 7 into 8/4 ohms, respectively, ACD?

Any amp can claim anything… but as for actual delivery - it can’t. Unless, that is, it has two individual and independent power cords feeding multiple power supplies. In order to achieve 200wpc x 7 continuously with all channels driven, it would require a whopping 3111 watts, or two 120V dedicated lines consuming almost 13 amps each!

An amplifier claiming 400wpc x 7 into 4 ohms, all channels driven, would require over 6200 watts! That’s 3 ½ dedicated 15A lines running at full power — or, perhaps, a mini self contained nuclear reactor in your home! Remember Three Mile Island? Those guys liked their music LOUD!"

From what I can tell the 7700/7500's don't have multiple power supplies.

Read the whole article. The All Channels Driven (ACD) Amplifier Test

The majority of large multichannel amps (up to 200W per channel) rely on a single 15A or 20A power supply. Some quick examples of big multichannel amps with a single 15A or 20A power supply include Outlaw's 7700 and 7200 (both 200Wx7), Lexicon's LX-7 (200Wx7), Emotiva's MPS-1 (200Wx7), and Parasound's Halo A51 (250Wx5) - there are others, certainly, but those came to mind. As you say, the basic physics (15A or even 20A circuits at 120V) says that you will run out of amperage before you max out all of the amp channels. Of course, the source material and speakers that would push seven or even five channels to those levels is pretty frightening to consider (and improbable, for that matter), which I think is why there's not a lot of fuss usually made about the reality behind the numbers.

Outlaw had an amp in the works that we may still see at some point - it was a 300Wx7 amp that they ended up going back to the drawing board with because of heat dissipation issues. It was going to have two separate power supplies (both of which I believe were capable of connecting to 20A circuits). Likewise, Anthem's Statement P5 (325Wx5) has two power supplies that Anthem recommends connecting to separate circuits.

Hair dryers: the common maximum wattage available in the US is 1875. This is mostly a resistive load with a small fan motor. If an audio amplifier were a pure regulator of power merely dispensing power as needed at 100% efficiency and presenting a purely resistive load, we could then reach just over 7 x 265 watts (RMS) of continuous power from a common 15A circuit in the USA or Canada.

Wikipedia articles on alternating current and electric power tell us that the peak voltage available from a 120 volt AC outlet is almost 170 volts and that the apparent power can exceed the real power if reactive power is a part of the equation. As our amplifiers employ sizable transformers and capacitors, reactive power is definitely a part of the equation. (More information here .)

Then there is the test article at the Audioholics site. If many of the manufacturers are using this test, where ‘continuous’ is not ‘continuous’, then it does make sense in a competitive environment to subject one’s own amplifier channels to a truly continuous test and put those numbers before the buying public when other manufacturers use the much less strenuous test? The interested consumer will perhaps read reviews that included bench testing and thereby some differences in amplification will be revealed. But the average buyer who frequents the larger chain stores and makes decisions on popularity of brand, looks, and specs printed next to the price may not readily understand why an Outlaw amplifier rated for 125 WPC might outperform the amplifier section of a receiver rated at 170WPC.

Bottom line: determining delivered power from an amplifier is not a simple matter of multiplying volts and amps. Measuring this power is possible through some mildly complex analysis of volts and amps delivered by the available channels, or by such means as equivalent energy delivered into a thermal system – if the power output of your amplifier would heat a liter of water as fast as a 100-watt plain resistive load would, then that amplifier is delivering an average of 100 watts over the same period of time, much longer than the above mentioned test.

By the way, I’d be more concerned with the thermal aspects than the power specifications. Who among us would expect to deliver 200 or 300 watts continuously to our loudspeakers and expect them to survive? Think of it this way (don’t do this, just imagine, OK?): take a spare loudspeaker enclosure, physically (not electrically) attach two 100-watt light bulbs to the woofer, seal the enclosure, then apply power to the lamps. How long until you smell smoke, or worse? Can you say “Easy Bake Oven” (which uses a 100 watt lamp maximum)? My loudspeakers are rated to 300 watts, but I wouldn’t expect them to remain unharmed if subjected to a continuous long-term average dissipation exceeding about 30 watts.

As long as my 770 amplifier can take my speakers cleanly through peaks exceeding 300 watts, I’m not concerned with using the amplifier output to turn my speakers into musically modulated heat sources (which they are, but on a small scale) for continuous 200+ watt duty.

While I agree on the gist of your post - the bottom lin eis reactive or not, if you can put out more than you take in it's a perpetual motion machine.

That article is rather curious. Their Mathematics are correct ( as far as I can determine ), however to say they prefer stated wattage to the 2 front speakers and the rest at lower power strikes me as an odd opinion. I would much rather have All channels at equal power/capability. Speaking of which does anyone know the Outlaw method of testing? Single frequency, frequency sweep, white noise etc across all channels? Just curious.

the 7700 os a class A/B amp. It cannot be measured that way.

Personally all I care about is sound quality, and as long as i can get that quality and the dbs that I will fill my room with sound an no distortion. I get that with my 7500. I cannot go higher than -7 dbs because its too loud for me.

While the math is correct, I think the article somewhat misses the point. What a house outlet can provide, or what a cable can handle has little to do with the unit can provide. Yes the cable will get hot, yes the unit will get hot. But from a pure specification standpoint, the unit can deliver the power. What the article does bring up, although not well, is the basis for the test to begin with. Having done a lot of UL/NTRL testing for medical products, they test for safety only. So as long as under their test conditions the unit is safe, it gets a label. It doesn't mean that under other conditions the unit won't perform better, albiet a bit unsafe.
I agree that its not what people can expect when installed in the home. The test needs to be clarified and changed.
If you think the home market is confusing, the automotive audio market is far worse. Little to no standards at all.

What I remember from school (long ago!) is that the cosine factor comes into play for these power ratings.
Also, if you run this amp at full power consider the efficiency- it's surely never over 45% for class B amplification.
Nice discussion though...
But never fear, I am building my own 7*240W @ 8 Ohms final right now based on Coldamp www.coldamp.com modules, and they said power ratings could be relaxed greatly for the surround channels, as the bass channels (my fronts are biamped) are the most power hungry.
Our power grid in Holland is 230V, but that should not make any difference for this discussion, only the amperage is less of course.
BTW- My 7700 is expected on Thursday, and I plan to rewire the transformers' primaries for series operation (effectively 230V), keeping my fingers crossed...
Or should I worry about the load per transformer obviously being different as they feed different amps?
And there's the 50Hz vs 60Hz issue, now what I remember running a 60Hz designed transformer on 50Hz results in the transformer getting warmer or was it the other way around?
Suppose the 990 has only one, so the trick won't work here, but I have a hefty step transformer ready to be used.

In all reality, the unit can be plugged into a circuit that has a 20 amp breaker, and in that case the typical 20 amp CB will permit a bit over 20 amps into a resistive load. So in real life a not so uncommon setup can feed 20(+)x120 watts into a device like our amp. I bet 2500 watts input wouldn't be out of the question at all, particularly for periods measured in minutes.

The efficiency of an A/B amp is also an issue. In order to get 200 watts at the speaker terminals, you'll have to input 240-250 watts or more of power. The difference is pooped out of the system in the form of heat.

I also find these claims to be dubious, but it seems that the industry is rife with them so all the vendors feel compelled to play the game even though a real electrical engineer would just roll their eyes at the numbers.

Cheers,