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Originally Posted by edisonmach
K1000 are the AKG "earspeakers" correct? I would guess that some type of impedence matchin would have to be performed for these to workf correctly with a standard headphone amplifer. Are these amplifiers mentioned matched in this manner or are some of the loudspeaker amplifiers? Excuse my ignorance on the matter. I have these available to me for use and have never put them to any good. If possible I would love to find an application for them.
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Not so much impedance matching. You'd need enough voltage swing from the amplifier.
For a headphones amplifier, you're more limited by current output than voltage swing.
It's more of the other way around for speaker amplifiers.
For speakers with their low impedances, you need a lot of current but less voltage swing.
Consider this:
To put 0.4 watts into a 4 ohm load (speaker), you only need ~1.26v but ~0.32A. This means the speaker amp can get away with a 3v swing as long as it can output the current required.
However, to put 0.4 watts into a 120 ohm load (K1000), you'd need ~7v but only ~0.058A.
Pushing 7v into a 4 ohm load, you'll need to output 12.25w. So you can't just use a low power speaker amp to drive the K1000's, it's less likely to have to voltage swing to drive them.
Similarly, a headphone amp using opamps may be able to give you a voltage swing of 18v p-p (24v supply & 3v off each rail for the opamp) but the opamps can only give about 0.045mA (for the higher end Burr Browns and AD chips). The voltage swing is enough to drive a pair of K1000's but the current output is still not sufficient to do so. You got to be pretty crazy to push opamps to output that kind of current levels anyway.
edit: semantic error