Me too, my Denon(s) and Marantz(s) all have those infinity fans on top but there for added insurance only, none of them had shutdown before the fans were added. ADTG might have his Denon(s) placed in such ways that they didn't get the recommended natural cooling, but I am just guessing. Hopefully he will tell us more.
Just an aside, don't we all notice the Yamaha photos someone posted earlier revealed an obviously larger enclosure, more heat sink area, but sadly, made of stamped metal instead of Denon's seemingly smaller but much better real heat sinks? Denon's design is actually smarter, choosing fans over size and weight. They ran hotter than Yamaha's, likely due to higher bias current used for the sake of reduced crossover distortions, and the overall cost might be lower because of the reduced weight that should result in lower shipping costs, just one example..
If you compare the look of the transformers, Denon's are very well shielded with copper wraps to offset the one advantage that Toroidal transformers offer, i.e. lower magnetic flux leakage. The Yamaha's don't seem to have the same degree of shielding.
For real heat sinks, like Denon/Marantz's (higher models), one can look to the Yamaha MX-A5000:
This is not directed at you, and am not choosing side, just making some factual observations. Just a by the way kind of thing, instead of making a separate post, and since we both are D+M users.
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