Quote:
I think what you may have meant was...an amp gain setting meant for higher impedance headphones = higher power output.
For example, as you increase the value of a resistor (in ohms) in a circuit, the current (amps) and power (watts) will decrease.
We're not concerned with voltage as much as power dissipation in watts.
As we increase the impedance (measured in ohms) of a headphone connected to an amp, the headphone's voicecoil will dissipate fewer watts (voltage x current).
For instance, I have an 8 ohm loudspeaker that is dissipating 100 watts from an amp. If I connect a 16 ohm loudspeaker, this new speaker will dissipate 50 watts. If I connect a 4 ohm speaker, it will dissipate 200 watts. Of course this is all assuming the amplifier is stable with such a low load impedance and such high wattage.
Power = Voltage * Voltage / Impedance
If you take a look at the
ZxR specs, You'll see that the headphone's amp power output with a 600 ohm load is 80mW. This must be the High Gain setting. My guess is that when you switch between these gain levels, a relay switches between feedback resistors to alter the headphone amp gain per the
TI TPA6120 datasheet...or it could be a digital resistor, but now we're just splitting hairs. Disconnect your headphones, and switch this setting back and forth; do you hear a click from the soundcard? Just curious.
ANYWAY
So what happens if we use 300 ohm headphones in the High Gain 80mW mode? The headphones now have to dissipate 160mW of power or 0.16W.
Now look back at the "Load Rating" of the HD600 = 0.2W. You might be able to safely use High Gain mode, but you'd be cutting it a little too close to your headphone's power handling limits for my tastes (assuming that "Load Rating" is Sennheiser's way of saying "Power Handling").
So, best to stick with Normal Gain.