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Seeing as how there are so many loopholes and it's so comon for companies to overstate wattage, I've heard an easy way to determine which of two comparable amps is more powerful is weight. (This obviously don't necessarily mean better or cleaner, just more powerful)


It seems to make sense as the amp section is where most of the heavy parts live. Anyone know how often or not this is a good factor to consider?
 

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The power supply transformer does add a lot to the total weight. You do need more iron to deliver more current from the wall without saturating the transformer.


The power supply capacitors also can be heavy. If you want enough reserve power for sustained high current operation or for musical peaks, these can be substantial.


The heatsinks for the output devices can also contribute. If a receiver can really run all 5 or 6 amp channels at the rated current of, say, 100W each, then you need a lot of heatsink and maybe a fan to get rid of all that heat to keep those devices from being zorched.


Heavy duty chassis are also indicative of better equipment, but don't necessarily add much to the sonic capabilities.


Weight alone probably isn't enough. If the continuous power ratings seem questionable, then also look for a dynamic power rating or dynamic headroom. This should be a good indicator of the units reserve capacity for handling peaks. A dynamic power rating of about 50% higher than the continuous level is respectable, that's almost 2dB of dynamic headroom. More is better, but that's usually only found in higher end gear or separates.


Also, look for a 4 ohm power rating. If the unit is rated for 4 ohms at all, that is a good indicator that it can supply higher currents. A 4-ohm power rating equal to or higher than the 8-ohm rating is respectable. A 4-ohm power rating double the 8-ohm power rating is ideal, though again that is usually found only on high end gear or separates.


Finally, I don't know the rules for rated power consumption, but it's always interesting when the power consumption rating on the back panel is lower than the sum of the rated power outputs from all the amp channels...


If you don't see a 4-ohm or dynamic rating, you can assume the receiver is a bit lacking, otherwise they would be proud to market it.


My new Marantz SR5300 has neither a 4-ohm rating or a listed dynamic rating. Even so, it seems very nice so far, and I doubt I would ever have all channels running at full power in my medium sized room. Probably not even 25% of full power...


HK seems to have some of the most conservative ratings of the low and mid-fi brands. Their components also seem to weigh a lot more than their competition.


Just my 2 cents...
 

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I don't usually put a great deal of confidence into Consumer Reports ratings, but their test results are usually respectable. They did test front channel continuous power output on some current receivers. Just for grins, here are the top 5 including ratings from manufacturer website specs:


Panasonic HE100, 23.1 lbs:

Rated 100Wx2 into 6 ohms

Tested 85Wx2 into 8 ohms, 112x2 into 6ohm, 45x2 4 ohm


Onkyo SR600, 24.5 lbs:

Rated 80Wx2 into 8 ohms, 105Wx2 into 6 ohms

Dynamic Rated 95Wx2 into 8 ohms, 160Wx2 into 4 ohms

Tested 109Wx2 into 8 ohms, 127Wx2 into 6 ohms


Harman Kardon AVR320, 32 lbs:

Rated 65Wx2 into 8 ohms

Tested 88Wx2 into 8 ohms, 105Wx2 into 6 ohms


Onkyo SR500, 18.7 lbs:

Rated 65Wx2 into 8ohms, 80Wx2 into 6 ohms

Dynamic Rated 85Wx2 into 8 ohms, 125Wx2 into 4 ohms

Tested 92Wx2 into 8 ohms, 110Wx2 into 6 ohms


Yamaha RX-V430, 21 lbs:

Rated 75Wx2 into 8 ohms

Tested 101Wx2 into 8 ohms, 115Wx2 into 6, 74x2 4ohm



Now here's one from near the bottom of their ratings:


JVC 6020, 19lbs:

Rated 100Wx2 into 8 ohms

Tested 98Wx2 into 8 ohms, 114Wx2 into 6 ohms


Draw your own conclusions:)
 

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My experience is that most of the amplifiers are so conservatively rated as to be absurd, especially at the 8 ohm impedance level. I have seen either meter readings or someone else's measurements on a fair number of amps in the 200wpc range, and they have all delivered well in excess of 200wpc - often 300-330wpc.


Note that I typically inhabit a relatively high level of the space - I have a Classe CA200 and a Counterpoint SA220, both rated 200wpc and deliver closer to 300wpc than to 200wpc - and retailed for over US$3K. This appears to be fairly common if not universal practice at this price point.


I have no evidence or facts, but I'd be much more cautious in the lower end of the market.


In my mind, a heavier amp just means that it weighs more. It has no direct impact on capacity or quality. *very* generally a heavier amp will have more power supply than a lighter one, but it can be difficult to distinguish between a transformer core that's heavy and a case that's milled steel, for example.
 

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Actually, the reverse of this hand-rule may be more useful. If the receiver is very light, then there is a possibility that it may be underpowered. Assuming similar designs, the lighter one should have crappier parts, which will limit how good it can potentially be. (This does not mean the heavier one is hitting the potential, of course.)
 
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