Paste and Copy Project: How much mW do different amps or amps/dacs have at different ohms? Help if you want!

[imackler]

So no idea what I'm doing but here is the result of my paste and copy search to compare different output power of different amps or amps/dacs. Basically, I wanted a sense of how much power a E11 had compared to a UHA-4 compared to a P4, etc...
 
As far as I know, this is the output per channel… There is a lot I don’t know here, but maybe some of you can clean it up/find it interesting. I included a couple desktops at the end for kicks. Feel free if you're interested to add others or give me stuff to edit.
 
I find it useful to simply look and compare what power an E7 has compared to a D4, etc.
 
Does anyone know if there is a way to predict the output power? If one has so many mW at 100ohms, can you predict what it is at 32 ohms or 300? Is there a formula or a ratio? The specs for the NFB12 (which is not portable) makes me think that there is.
 
Ipod Classic
10 ohm reference load at 29.7 milliwatts
 
UHA-4 (Portablee Amp/Dac)
(Taken from Leckerton's site but don't understand why some are so low...at different gains? Honestly, these numbers don't look right in comparison to others.)
 
Max output power:

1. 20 mW into 16 ohms
2. 40 mW into 32 ohms
3. 50 mW into 100 ohms
4. 15 mW into 300 ohms

 
UDAC and UDAC 2 (Portable Amp/Dac)
Power output: 80mW @ 16-Ohm
 
Fiio E7 (Portable Amp/Dac)
Output Power: 150mW (16Ω); 16mW (300Ω)
 
[size=10.5pt]Ibasso D2 (Portable Amp/Dac)[/size]
[size=10.5pt]Output power[/size][size=10.5pt]：[/size][size=10.5pt]Up to 100mW into 32[/size][size=10.5pt] Ω[/size]
 
[size=10pt]Ibasso D4 (Portable Amp/Dac)[/size]
[size=10.5pt]Up to 230mW into 32[/size][size=10.5pt] Ω[/size]
 
[size=10.5pt]Ibasso D6 (Portable Amp/Dac)[/size]
Output power：Up to 650mW into 32Ω
 
[size=10.5pt]Soundmagic A10 (Portable Amp)[/size]
Maximum Output Power :  70mW (33Ω)
 
E11 (Portable Amp)
57mW into 250Ohm (From quote from E11 Thread)
 
[size=10.5pt]Ibasso T3D[/size]
[size=10.5pt]120mW  (into 32? I'm guessing) [/size]
 
[size=10.5pt]Ibasso PB1[/size] (Portable Amp)
[size=10.5pt]1400mW into 32[/size][size=10.5pt]Ω[/size]
 
[size=10.5pt]Ibasso PB2[/size] (Portable Amp)
[size=10.5pt]Up to 2500mW into 32[/size][size=10.5pt]Ω[/size]
 
[size=10.5pt]Ibasso P4[/size] (portable Amp)
Output power: 600mW into 32
 
NFB12 (Desktop Amp/Dac)
[size=10pt]3500mW/25 ohm
1800mW/50 ohm
900mW/100 ohm
300mW/300 ohm
150mW/600 ohm[/size]
 
Yulong D100 (Desktop Amp/Dac)
900mW at 32Ohm
130mW at 300Ohm
 
E9 (Desktop Amp)
1000mW (16Ω)
 80mW (600Ω)

 

[qusp]

only from the same device can you predict it (and only on a surface and rather general level) using a variant of ohm's law and even then it may not be reliable, as the output impedance of the amp, the capacitance and inductance of the cable, or some sort of current limiting could start to effect the results. also different amplifier topologies behave differently into various loads and at different frequencies.
 
the nfb12 numbers you have there is simply a direct effect of ohm's law  current = voltage/resistance or I = V/R and then I x V = W (wattage/power) this is only for a purely resistive load, which a transducer is not. written as V = I x Z which is the more complex AC voltage and Current variables and Z is impedance, which varies over frequency. is reasonably accurate at a given frequency, but real music is not a constant frequency. so sometimes you will see rated power given @ 1khz and they usually mean a sine wave. 
 
then you various other factors like the output caps if there are any, the power supply, whether its a single ended, or balanced amp (balanced or bridged amps will put double the power into double the load impedance, given double the power, they do not automatically give double the power as is often said on this forum)
 
so short answer is no, there is no way to reliably tell how much power a given amp will give into a different load impedance and audgd's rather linear response table there is ermmm strange to me, unless they also state at what frequency and even then other factors will come into play