A decade ago, someone posted Stereo Review power output findings on the web. What it showed was that manufacturer's ratings mean nothing. I seem to recall where a Denon receiver rated at 90X5 or 100X5 only actually met its rating with one channel driven. If all channels were driven, it struggled to produce more than 20 or so wpc.
All receivers and amps are not created equal. Discrete channels reduce crosstalk. This is plainly audible. Better and bigger power supplies mean the difference between producing 20% more than the rated power with all channels driven and producing 20% of the rated power when all channels are driven.
Bill
This seems right to me based on the educated but differing points of view always put forth on this topic both in this forum and in print and my own experience. Fact is, my Denon AVR 3300's 105 w/c will not sound as good as Wid's Rotel at 120 w/c when pumping 5 chans in spite of the fact the 15 w/c difference is mathematically insignificant.
The fact is, the Rotel amp will deliver its full rated power, or more, to all channels under all circumstances. My Denon will give me probably one Chanel of 100 watts. With 2 channels running hard it starts to clip at 78.6 watts (.016% THD). At 5 channels pumping hard - as is very common now with DD and Surround Music - my AVR will not give me 100. I hope it is more than the 20 mentioned above, but clearly not 100 or even 78. I think that is the difference between the lower-end AVR claiming 100 (e.g., Denon 700 series or Onkyo 700 series) and the better AVRs (e.g., Denon 3808 and Integra 8.9) and the moderate separate amps (e.g., Rotel and Bryston 9B). One example I found interesting, if not completely understood, was on the Integra website where between two models with only 10 w/c difference between them, there was a 100% increase in current capacity from 35A to 72A. I'm not positive how the current/volts/watts equation works, but looks like the 72A current supply could deliver more of the 140 promised watts than the 35A model when I beg for it.
I think much of the debate stems from lower listening levels. Much is the same there and audible differences are minute and difficult to describe if heard. But at the edges of the performance envelope - either in terms of dBs or dynamic peaks - the more expensive amps distance themselves in very noticeable ways. Some people don't listen at those levels so the amp sections all sound the same to them and bear out the simple math.
I like to listen to music at very real levels (when I can). Whether that is an acoustic guitar on Dave Mathews, or Ray Brown's stand-up bass plucking away, the accuracy of the illusion is created when the instruments and voices sounds as if in the room. At those levels (upper 90 - low 100 db, to me, in my room) all watts are not the same. At the edges of the amps envelope math does not tell the whole story - microfarad supply capacitors and other power widgets and do-dads that you can't find on the spec sheet seem to make a significant difference. i guess that is where some of the money for Krell and Bryston and McIntosh, etc., goes and why I may appreciate those amps when others here rightfully would not ever notice a difference.
