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
Not meaning to hijack my own thread but since Mjcmt brings up McIntosh and autoformers, I bought some Speltz speaker cables and an IC from him some years ago. I recall he was also offering something called a Zero Box.

I'll go and search on this topic and see what I can find, but does anyone have any comments on Speltz's Zero Box and under what circumstances using them might be of benefit. Again, I am unhappy with my current speakers: I don't know if it is the amp or the room, or I just don't like the speakers but I do think there might be a mismatch in my system.

System:
Speakers: PBN Montana XP
Ampilifer: Butler Audio 5150 (currently in use in 2-channel mode only)
Pre-amp: Lector Zoe
Source: Raysonic CD-128
"Again, I am unhappy with my current speakers: I don't know if it is the amp or the room, or I just don't like the speakers but I do think there might be a mismatch in my system."

What is it that you don't like about your system and what do you expect from an upgrade?
Fin,
I think that is indicative of sn amp with higher output impedance, usually but not always an attribute of tube amps. An amp like that will probably perform best into higher impedance speakers, ie 16ohms, which is not common. Its a special breed that needs a special mate. My recollection is that pbn is probablyof the more typical ilk, impedance of 8 ohms or less. Probably not the ideal pairing, but workable.
I have seen some pnm impedance measures in stereophile that show wide impedance flucuations from 4 to 16 ohms at various frequencies. Far frm the constant high impedance that an amp like that would probably do best with.
The OP's Butler Audio amp is not a full tube design. I believe it is solid state with a tube input stage. Therefore it will not necessarily need a speaker with a flat impedance.

Finsup, It sounds like you are not happy with the sound at present. There are allot of reasons why that could be. If you could explain more about what you're not liking and maybe some details about your room dimensions maybe someone can give you some suggestions.