The issues of equipment reliability runs across both camps. In my article on Onkyo AVR, I criticized similar issues to the amp in question here:The objectivists often attempt to prove that the subjectivists are wrong, or they ask, sometmes demand, evidence, proof or verification of the other's observations. Or in the case of that amplifier with the heatsinks on the bottom, they point out that the design is flawed without solicitation for comment. That leads to acrimony and a hostile environment for discussion. The subjectivists often just want to be left alone to enjoy their music or they want to share their experiences on friendly forums without having to prove their opinions. Many have left this forum for friendlier places.
Unfortunately we see a recipe for a accelerated failure of a capacitor in this unit. As you see in Figure 4, the rectifier, the large flat device, is touching the capacitor. The large size of the rectifier indicates that it is designed to dissipate fair amount of heat. Due to direct contact, the heat directly couples to the capacitor causing its operating temperature to be much elevated had there been an air space between the two components. While there was an easy fix of simply bending the rectifier away from the capacitor, this is the kind of flaw that should have been caught during assembly or better yet, more distance designed into the PC board that holds the components between capacitors and heat generating sources.
More disappointing though sadly very common is the temperature rating of the capacitor. As I have marked, the capacitor is the common 85 degree C rated type. While this is plenty high for most electronic circuits, it is not in the vicinity of high power devices and inside of a cramped AVR with so many channels of amplification all generating heat. I would like to see capacitors rated at 105 degree C in such scenarios. To wit, next time you are shopping for PC desktop power supply, you may want to peer into its venting slots and see if you can read the temperature ratings of the caps. If they are 85 degrees and not 105, I would walk away from it. High quality ones will always have 105 degree C capacitors given the very close proximity of them to the high power components.
Figure 4: Power supply rectifier and filter capacitor touching, leading to shorter life.
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The biggest disappointment is not the capacitors but the two fans. They are buried under the two metal square boxes one each side of the power supply. They are slanted 45 degrees, blowing sideways onto the heat sink. You don’t need a degree in physics to realize that air blown across the heat sinks is not going to uniformly cool them. The fins closest to the fan will get the bulk of the air movement, and the rest get substantially less. And the air that does get through is turbulent due to obstruction of the fins.
Proper cooling would call for smooth air movement between the fins which would call for the fans to be above or below the heatsink. That would make the unit much taller which was likely the reason it was not used. This compromise means some of the amplifier channels will run hotter than others, and in theory, have shorter life.
To add insult to injury, the fans kick on based on specific volume level rather than heat generated. Better design calls for a temperature sensor to keep the fans off as much as possible if the unit has ample circulation. But no, as soon as you turn up the unit, the fans click on saving a few cents in component pricing, but bringing with it the higher noise of the component, and shorter fan life.
Actually the right design would have called for a much larger heatsink so that no fan would have been necessary. That of course costs more money as heatsinks are expensive as is space to house them and shipping cost to get us the unit from far away manufacturer. So compromises were made, hoping one wouldn’t notice. And probably no one does.
I am being harsh here since there is an unwritten rule that in the home consumer market that amplifiers are fanless and silent. Professional units use fans because they live in much harsher environments of cramped racks and outdoor applications (e.g. for live sound). But home units usually live in homes with less hostile temperature ranges that allow passive cooling if one does not aim to reduce cost. For the $1,000 that I paid for this AVR, it would have been a fair expectation to get an amplifier without fans.
Objectivists are the types that buy these AVRs instead of discrete amps high-end folks use. Yet, there was no protest. Instead, I was greeted by this first reply:
Nice teaching Amir.
So ask again, why do you seek protection for sharing of this technical information while the other camp does not? Why is it that they don't find it insulting but you do?