2. amps-preamps
  3. 153225-130247

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? 
redstarwraith

Showing 3 responses by listening99

listening99
172 posts
 
Instead of starting a new thread, I thought I would drop in a question on these same issues: I've been running a Nuforce STA200 with two 8ohm speakers, horn loaded, so the sound emerges with little effort and the amp runs cool. However, now I'm buying Tekton Moabs and they push a 4 ohm load. The Nuforce is stated to be suited to 8 ohms, not 4. The Moabs are efficient, running at a rated 
  • 98dB 2.83V@1m sensitivity
If the speakers run easy, what am I doing to my 8ohm amp, were I to hook them up...?
listening99
172 posts
 
The idea is to replace my existing speakers with two speakers that present 4ohms resistance/each. I understand the speakers are efficient, although the manufacture statistic of 98dB is probably overstated. The hope is that the amp functions well at the lower volumes I would listen to, habitually. I mean, if a speaker can produce 90dB with less than a watt of power, I should have very little difficulty, sitting about 8-9' away, and then the amplifier is basically loping along, even with two 4ohm speakers, right? I keep hearing the Moabs are amazing and no one is complaining about the 4ohm load... 
listening99
172 posts
 
@atmasphere and others, when I read, for example, the power rating for the parasound A 23+, it states:


  • 160 watts x 2 @ 8 Ω RMS, both channels driven
  • 240 watts x 2 @ 4 Ω RMS, both channels driven


My assumption has always been that the top 8ohm figure is relevant to the use of not one but two 8 ohm speakers, as is stated on the website. Your figuring seems to suggest that playing two 8 ohm speakers would imply the second figure, or 240 watts from the combination of the speakers, or 4 ohms?

The also suggests, following what I think I understand of your claim, that few of the amplifiers on the market should be used for two 4 ohm speakers, as they don’t often state a 2 ohm power rating...
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