2. amps-preamps
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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? 
128x128redstarwraith
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?
audiozenology
362 posts
 
27 amps is 1500 watts into 2 ohms. 60amps is 7200 watts. 60amps would require a bus voltage of 120V at 2ohms, phase-angle aside. I think the number of speakers that drop below 1.5 ohm approaches a handful and even the number that drop much below 2 ohms are uber expensive and won't be matched with a $1,500 amplifier. 60 amps at 1.5 ohms requires a 90V bus voltage (approx). Odd of the odyssey amplifier having a 90V bus supply are pretty much 0. Given it's power rating, it is much more likely to be close to 35-40V.  That 60A specification is pretty meaningless ..... not to mention 60A would drag down the power supply capacitors pretty seriously, further limiting the practicality of delivering this much current.



audiozenology
362 posts
 
Tube-amps sometimes "seem" more powerful as their distortion is typically more pleasant when they clip, but they are still clipping.
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