There are few variables and they are easy to understand if you take the time to do it. Some people want it to be complex because THEY do not understand it and wish that others do not, so that keeps them on level ground.
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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The main usefulness of amplifier power ratings, IMO, is that they can make it possible to determine a reasonable approximation of how much volume (i.e., sound pressure level, or SPL) can be produced by a given amp/speaker combination at a given distance. In doing so they can make it possible to **rule out** candidates for purchase that would not be suitable in that respect, relative to the particular listener’s preferences. Here is a calculator which can be used for that purpose: https://myhometheater.homestead.com/splcalculator.html In using that calculator an attempt should be made to find actual measurements of the sensitivity of the particular speakers, rather than published specifications which are often optimistic by a few db. If Stereophile has reviewed the particular speaker the measurements section of the review will provide a good indication of that. In using that calculator it should also be kept in mind that speaker sensitivities are most often specified based on an input of 2.83 volts, rather than 1 watt. 2.83 volts into 8 ohms corresponds to 1 watt, but 2.83 volts into 4 ohms corresponds to 2 watts. So in the case of a 4 ohm speaker the response to an input of 1 watt will usually be at least 3 db less than the published specification. Regarding output current specs for amplifiers, such as 60 amps, 100 amps, or other such outlandishly high figures, those are among the most useless of specs. As explained in the following thread what they usually represent is how much current the amp can supply into a dead short (i.e., zero ohms) for an unspecified tiny fraction of a second. And as indicated by Atmasphere in that thread they might even correspond in many cases to the output of the amplifier’s power supply under such conditions, rather than to the output of the amplifier itself: https://forum.audiogon.com/discussions/current-limit-onset-definition Atmasphere has also explained in other threads that one reason some very low powered amps may sound more dynamic and powerful than their power ratings would seem to suggest is related to how the distortion they produce varies as a function of output power. In particular, single-ended triode (SET) tube amps, which often have power ratings in the vicinity of 8 watts or even less, can sound much more powerful than that because our hearing mechanisms use certain harmonic distortion components as loudness cues, and the distortion produced by SET amps varies from being vanishingly small at low power levels to being very considerable as their maximum power capability is approached. The result being a subjective perception of greater dynamics and more power than the ratings would suggest. Generally speaking, though, once candidates that can be determined to be unsuitable matches have been ruled out (such as by determining that the pairing would not be capable of producing acceptably high SPLs) the best way to determine a preference is usually by some combination of listening, trying to determine what kind of amplification the speaker manufacturer prefers, and researching what owners have found to be suitable amplification for the particular speakers. Regards, -- Al |
P.S. to my previous post: The SPL calculator I linked to assumes box-type dynamic speakers, as opposed to planars (i.e., Maggies or electrostatics) or "line source" speakers. In those cases the calculator will typically underestimate the SPLs that can be produced at a given distance for a given input power, by several db at typical listening distances. SPLs produced by planar or line source speakers fall off less rapidly as listening distance increases than in the case of box-type dynamic speakers. Regards, -- Al |
Power and hearing perception are logarithmic. Like the earthquake richter scale. A 100 watt amplifier is only twice as loud as a 10 watt amplifier. However higher the power the More relaxed is the output. Also when buying an amp always look at the power output in watts RMS into 8 ohms CONTINUOUS output. The rest is is marketing information trying to make it look better than it is. |
Read the review for this Proton that I own. A lowly 40wpc but 6db of headroom. It makes my DQ 10's just sing compared to the Yamaha SS receiver I was previously using at 95wpc in 2 channel mode. I don't know a whole lot about the 'techy' stuff but I believe it's a class g/h? Incredible sounding 'little' amp for sure.....
http://www.hifi-classic.net/review/proton-d540-410.html
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