CJ said:
tired of gettin eardrums dead for 3 days due to massive volume levels being triggered for reasons unknown.
,
is there a zener i can slap across the bones so i don't get bit?
they should have one built in,
You understand that there is a relationship between the voltage limit, the impedance, the h/p sensitivity and the corresponding max SPL. So you'll have to tune the zener value with each particular h/p.
You want to make the system bilateral, treating positive and negative voltages identically, so you'll need either a bridge (1.2V threshold), or a back-to-back arrangement. The lowest value zeners, at 1.2V, will limit the absolute voltage at 1.8V in b-to-b configuration, thus limiting power at ca. 100mW into 32 ohms cans (considering that under clamping, the waveform is almost square), which is enough to fry your ears. You could use just diodes, that would limit the p-p voltage to 0.6V (2 diodes) or 1.2v (4 diodes), resulting in 11 mW or 44 mW. Not too fine resolution. In addition, the onset of distortion for sinewave is at half the limiting power.
Finally, there is a danger in putting zeners or diodes across the input, since it could damage the amplifier.
I have designed dozens of studio headphone systems, I always installed a resistive network that limits the max spl, protects the amps, isolates a faulty can when it fries and ensures more or less consistent power whatever the headphones impedance.
BTW, there is a new regulation that limits the SPL produced by earbuds and headphones available to the public at 94dBspl for a
voltage of 75mV rms. So h/p manufacturers are hastily modifying their products in order to comply. I've been consulting for Audio Technica on this subject, which is not utterly trivial.