Originally Posted by M Code
Pretty simple math...
The AVR's power supply has the capability of driving 160 watts total (stereo mode) AC line 120V, the rest is how many
channels are being driven.. Since the power supply is common
to all channels its total VA capacity
is the limiting factor for power output. The power output spec may vary up to 5% due to other internal circuits/factors but this will put U in the ball park.. Especially pertinent if the brand only chooses to provide only
the higher 2 channel number
Just my $0.05...
while it is widely known that typical receivers cannot supply two-channel rated power to all channels because of power supply limitations, that does not mean that their power supplies are limited to being able to supply only the full power for two channels. A seven channel 100 watt per channel receiver would need a power supply that could support 700 watts to hit full power on all channels simultaneously. But we know they can't, most likely. But in my grade school matha classes, 600, 500 and 400 were less than 700.
If facts are relevant to your thinking, take a gander at the testing for the Denon 4520 at http://www.soundandvision.com/conten...ver-test-bench
it is rated at 150 WPC, two channels driven, and so in your calculations, you'd expect to see 300/7 or just about 48 watts per channel at 7 channels driven. But that's not what happens. at one percent distortion, it tested out to provide
190.7 two channels driven, for a total of 381.4 watts
145.3 five channels driven for a total of 726.5 watt
121.7 into seven channels for a total of 851.9 watts.
Here's an Onkyo, the Onkyo TX-NR828 (again one percent THD, at 0.1 percent the numbers are lower but the trend is the same. Rated at 130 WPC, two channels driven.
172.1 watts two channels driven, 344.2 total
125.5 watts five channels driven 627.5 total
96.8 watts, seven channels driven, 677 total
Power supply isn't the only thing that limits output. Otherwise we would not need output stages, you could just hook up the power supply to the op amps in the preamp section and let them rip. But in the real world you need output transistors, which have their own operating envelopes, to supply the power. That other amplification device, the tube, is more familiar to me. No matter what I put into the power supply, I cannot get more than about 20 watts out of a pair of 6V6 output tubes (okay, 30 with the JJ, but it's kind of a super-6V6). If I want 60 watts, I can use four 6V6s instead of 2, or I can use a pair of 6L6s. But I won't get a hundred watts out of either of those setups. Would need, in typical use, four 6L6Gcs to get around a hundred musical instrument watts (no rules, but probably around 5 percent THD for all those output ratings in real amps. I Own a 6L6 amp that's rated at "only" 45 watts . . . because of how the tube is used in the circuit, which in part is defined by (or for the designer, defines) the power supply.
from the real world test numbers it is clear that neither the output devices' limits nor the power supply's capability by themselves define total power that will be available driving multiple channels simultaneously
PS looking at the soundandvision testing for a Yamaha or two and a Sony, they seemed to be limited much more nearly like your assumption, which frankly surprised me. Long time since I was researching power numbers for a receiver purchase and I guess the better performing (from a pure power perspective) ones that I focused on are what stuck in what's left of my brain. SO there are indeed some units that look like your assumption would predict, and others that don't. OF course once you get into standalone power amps, nobody's (well almost nobody's) all channel driven numbers are below the two channel rating, because they have the power supply and the heat dissipation ability to do it "right."