One of the things that I always notice when I’m shopping for an amp is the fact that manufacturers almost never stick to a standard of listing the specifications, particularly with the output numbers.
Some manufacturers will list power output for a few relevant impedance levels (16, 32, 50, 300, 600)
But others will just list a couple (16, 32)
Does any one know if there is a way to get more meaningful information from the provided specs?
In essence, from the known listed specs, is there a way to extrapolate/interpolate the power output for intermediate values? Say, 150 ohms?
And if there are any electrical engineers out there, forgive me. It’s been a while since I’ve taken E&M
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Ideally, output power would be displayed as a graph with Resistance on the X and Power on the Y Axis at a given frequency (1000Hz for example).
As is, you could break out Ohm’s law (as I did further below) to find out: Without knowing the voltage the amp puts out, your work is very much worthless.
You could offcourse assume the transistors or MOSFET’s * are right at the edge of their saturation region (for semi-conductor based amps, 0.4 to 0.8V), the resulting error bars in the graph make the exercise worthless though.
*(I have no idea how Tubes work)
"This is easy!" he thought
Technically Ohm’s law for AC circuits is to be used. As headphones are only a resistive load, you can still use the DC forumla: U(V) = I(A) * R(Ω)
Insert the above forumla for U in P(W) = U(V) * I(A) to get P(W) = I² * R(Ω) and… this does not help much, does it?
Simple reason: When you change the resistance, the voltage drop changes meaning the current is different.
TL;DR
You can’t.
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That makes sense.
So it sounds like it really needs to be tested rather than calculated.
Is there a resource out there that provides results to such testing?
I’ll have to save this for later xD
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