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? 
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clearthink
1,421 posts
 
audiozenology"amplifier power tests, right or wrong are made into constant resistance loads"

This is true of course when amateurs, hobbyists, and inexperienced users conduct such tests but when performed by experts, engineers, and designers a much more thorough, complete, and extensive composition of tests is undertaken to accurately assess how a Music Reproduction System component will perform in real-world conditions by the end user.
atmasphere's avatar
atmasphere
11,965 posts
 
Because that would suggest that ALL amplifiers with different operations classes, types of FET and wiring singel ended/Push pull. Gives the SAME constant and relationships so only from wattage and resistance you can get the I and V.
This is correct even though you don't believe it. If a given amp makes a certain power into a certain load, then it will be making exactly the same voltage and current as any other amplifier that can do the same thing.

What might be tripping you up here is output impedance plays a role. If the amp has a higher output impedance, more of its output power will be dissipated in the output section itself rather than the load when presented with a low impedance load. Since no loudspeaker is a flat impedance from top to bottom, this means that different amps can sound different, even though at certain impedances of the speaker they might all make the same power.


To further muddy the waters, not all speakers are meant to be driven by amps with a super low output impedance, while others are. For more on this see:
http://www.atma-sphere.com/Resources/Paradigms_in_Amplifier_Design.php
audiozenology
362 posts
 
Oh come on Clearthink. You can do better than that. I am not sure that rant is even worthy of inclusion in my book, "Clearthink's Practical book of Impractical Rants". I have come to expect much more of you.
audiozenology
362 posts
 
JerryBJ,

No to belabor a point, but someone that accuses others of trolling I understand has even sent private messages to people asking them to report threads they did not like.
delkal
110 posts
 
In general if an amp can double down (100wats @ 8 ohms, 200 @ 4, 400 @ 2) that means it has a well made power supply and can supply the necessary current.   It also usually means there is usually good power reserves to cover transient peaks.
The only reason all amps don't all double down is because the designer got cheap and the power supply can't keep up.
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