this post was submitted on 14 Sep 2023
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How can they estimate it with a standalone DAC? I can understand that it can be calibrated when using a wireless headphone/earbuds (although it probably would be different depending on what the shape of the ear is, and what tips/pads you're using), but for a standalone DAC it sounds really strange since different headphones have different efficiency and it would be impossible for the amp to know what it would be, right? I have very efficient IEMs that get very loud even on very low volume when plugged to an ordinary USB-C DAC (one click above zero is a bit too quiet, another click is too loud), but on some larger overear headphones I have, even the max volume on the same DAC will be pretty underwhelming.
Even if the amp can detect the impedance of the headphones, it won't know the energy conversion efficiency... right?
I'm guessing the dB is not absolute volume, but relative dB (to measure amplification), so if you plug the same headphones into different amps, and give them the same source and the same dB setting, you probably will have different listening volume at the end.
I'm just a layman, so I might be missing something crucial.
As someone else said, I'm referring to the Qudelix where you can input the Impedance and Sensitivity manually
I believe you’re correct. DACs obviously can’t determine volume at all, but amps can try to use the impedance to create an estimate.
This probably isn’t accurate though. If you really want a good estimate, you would have to calculate it with current voltage output and the specs of the headphones/IEMs in question.
I’m just a hobbyist too, but my headphones are extremely inefficient so I’ve spent some time looking into this. Too bad we don’t have oratory here
I guess it might be possible to calibrate an amp for true volume if you calculate it, assuming such a feature exists (I never actually owned a dedicated amp, much less a fancy one, so I have no clue if such a feature exists), also I assume that overtime headphone efficiency will reduce as the permanent magnet gets weaker if exposed to high heat (no idea if forgetting the headphones in a car in summer would be hot enough to make a meaningful difference though) or dropped repeatedly (though I'd wager the headphones will stop working before the magnet itself in such case).
Some amps do indicate how much power they’re outputting. The little portable dac/amp Qudelix 5k is $100 and does this. I think it also has fields for impedance and sensitivity, wherein it calculates SPL (dB), but I don’t actually have one so I’m not confident.
That's pretty cool.