This isn't necessarily true anymore either. Take a look at the bench test for the Denon E400 and the more expensive Yamaha Aventage 730. The Denon beats it in 2-channel by a little and stomps on the Yamaha into 7 channels. I don't think it's the protection circuit and Yamaha simply has the weaker power supply in their receivers at this price point.
Denon AVR-E400 AV Receiver Test Bench | Sound & Vision
Yamaha RX-A730 Network A/V Receiver Test Bench | Sound & Vision
Maybe I am reading this wrong?
2 channels
Yamaha @ 4ohm
0.1 percent distortion at 145.1
1 percent distortion at 183.8 watts
Yamaha @ 8ohm
0.1% distortion at 115.5 watts
1% distortion at 134.7 watts
Denon @ 4ohm
0.1 percent distortion at 93.3 watts
1 percent distortion at 166.4 watts
Denon @ 8ohm
0.1 percent distortion at 130.0 watts
1 percent distortion at 116.5 watts
The all channel numbers are out of whack in comparison, but that seems strange given the two channel performance numbers, doesn't it?
I will also say that a common gripe on Yamaha's entry level AVENTAGE pieces is poor video processing, but I never use that feature and always set up pass through to the display.
Lastly, on the power supply, amplifier quality issue: With the sample our rep gave us Yamaha listed 2ohm specs. So I hooked up 3 pair of 8ohm speakers off of the front L/R channels to see if it would blow up or go protect. It didn't! It played all day at our design center in the warehouse fairly loud. other than getting hot, I thought this was amazing from a receiver to be honest. Durability with receivers is my number one concern and I thought this really spoke volumes as to the quality of build in the Yamaha stuff.