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Watts and power

Can somebody break it down in layman's terms for me? Why is it that sometimes an amp that has a high watt rating (like, say, a lot of class D amps do) don't seem to always have the balls that much lower rated A or AB amps do? I have heard some people say, "It's not the watts, it's the power supply." Are they talking about big honkin' toroidal transformers? I know opinions vary on a speaker like, say, Magnepans - Maggies love power, right? A lot of people caution against using class D amps to drive them and then will turn around and say that a receiver like the Outlaw RR2160 (rated at 110 watts into 8 ohms) drives Maggies really well! I'm not really asking about differences between Class D, A, or AB so much as I am asking about how can you tell the POWER an amp has from the specs? 
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erik_squires
15,948 posts
 
I really don't like the class stereotypes. I know a lot of Class D that have got tons more balls than some class A amps.


I currently listen to Luxman. They have more bass spunk than both a Parasound and Class D amps I've listened to.  So, in this class one particular class A/B amp beats another Class A/B and a class D.


Unfortunately some will always read this as proof that a Class A/B (the Luxman) beats all Class D.
millercarbon's avatar
millercarbon
12,531 posts
 
I'm not really asking about differences between Class D, A, or AB so much as I am asking about how can you tell the POWER an amp has from the specs?


Long story short, you can't. Its not only Class A, etc, but even among amps within the same class. The McCormack DNA amps for example have greater apparent power than a lot of other SS amps that test the same or higher. Its widely known that "tube watts are greater than solid state watts" simply because virtually all tube amps seem subjectively to have the power of SS amps rated twice as much. Even within tube amps there are plenty of 30 watt amps that seem as or more powerful than 60 watt tube amps- even though they may be running the same tubes!

Just a few of the many reasons why watts are one of the least important specs in all of audio.
audiozenology
362 posts
 
Mainly it comes down to headroom. Many amps can cleanly play short term peaks higher and sometimes much higher than their continuous power ratings .... Except pure Class A which are limited to their rated power.


Mainly it is a factor of power supply capacitance, regulation and sometime feedback (that can negate power supply ripple). How beefy the output stage is can come into play as well.
johnto
981 posts
 
Magnepan usually recommends getting an amp that will double its 8 ohm power at 4ohms.
stereo5's avatar
stereo5
6,280 posts
 
No two 200wpc amps are the same. It has to do with-current.  A
200wpc Class D amp may only put out 27 amps of current per channel, while a 150wpc Odyssey Class AB amp puts out 60 amps of current per channel.  Guess which amp sounds more powerful?
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