When an amp puts out 90 watts....


into 16, 8, or 4 ohms, what does that tell me about the amp? I am use to seeing an amp's output increase, sometimes even doubling, when going from say 8 ohms into 4 ohms.

The amp in question is the Copland CTA 506.
finsup
Rrog: It is the "norm" for me and, because it matters in my system, it's why I have a Krell 400cx driving my Thiel CS6s. My point was that the vast majority of amps do no comply with the doubling of power by the halving of impedance from the incrementals of 8 to 4 to 2 Ohms. Only a handful of manufacturers install power supplies robust enough to do this.
If you start with a reasonably powered amp and know the speaker impedence and efficiency are also reasonable, and act reasonably, you don't need to spend another moment on this power issue. Copland stuff is well regarded and I suggest you just set the whole system up and avoid the avalanche of opinions you could subject yourself to regarding room treatment, tiny wooden speaker wire bridges, gigantic power regenerators, fuse direction, and hairstyle tips...however, MY opinions are to be cherished as True Art and a gift to the reader...I'm a giver.
You should have just said so. List your whole system and some basics on your room. I'm sure someone will be able to point you in the right direction. As far as room placement goes, thats a great place to start. You'll learn a lot just doing that alone.

Maybe I will start another thread later but really, my reason for asking stems from reading a couple of different amp threads. There was a lot of discussion about impedance, slew rates, etc. and some calling out others for wrong information, etc. I guess I just want to have enough information to be dangerous like some of you other guys. :)

But seriously, I could not remember any information about amps delivering the same power into different loads and that is why I asked. Now I know why that is the case.

If you start with a reasonably powered amp and know the speaker impedence and efficiency are also reasonable, and act reasonably, you don't need to spend another moment on this power issue. Copland stuff is well regarded and I suggest you just set the whole system up and avoid the avalanche of opinions you could subject yourself to regarding room treatment, tiny wooden speaker wire bridges, gigantic power regenerators, fuse direction, and hairstyle tips...however, MY opinions are to be cherished as True Art and a gift to the reader...I'm a giver.

Wolf, I am a true connoisseur of your nuggets of wisdom...
Not only is consistent power output typical of tube amps, but also McIntosh amps that use autoformers have a stable power into all impedences.