Secondly measurements of course are important but it doesn't tell you anything how a specific device sounds. This is not unrelated completely but you can't take conclusions from measurements. To keep it simple: Have ever ever measured an Valve amplifier or a phono record player? If you measure them all you will throw them all in the bin according to the reviewers opinion. This is of course bull shit. Valve amplifiers can sound really nice and so do phono record players! Same goes for Audio-GD, it is completely designed around a non feedback amplifier and they do not measure brilliant but they do sound awesome! You can put a Class-D amp next to an Audio-GD amp. The measurements are great of the Class D amp but the sound isn't. Usually its clean and boring sound.
This is all true, but I'm surprised this community doesn't already know this? Everyone in the hobby knows this. Sorry, I'm new here; I just appreciate seeing measurements for things I haven't seen measurements for.
Anyway, measurements are important, but they don't tell you how something sounds. They will tell you how well circuits are designed and soldered, and they'll definitely tell you whether something is defective. There are some metrics, like seeing even low order dissipating harmonic distortion, that'll imply some tubey euphorics in the sound, but most measurement metrics are diagnostic.
The only way to figure out "what source chain will pair well with
this headphone" is by auditioning it. DAC and AMPs, measuring well enough to be "well made", will sound different from each other.
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Example:
This is the noise and harmonic distortion comparison between the SDAC and the OL DAC. What should be one's take aways here?
If you say: The SDAC is better cuz it has lower noise, I'll laugh at you.
The truth is both noise floors are so low that it doesn't matter. In other words, when it comes to noise, both PASS. What ends up mattering just a bit more is that the OL DAC has only lower order harmonic distortion,whereas the SDAC has more higher order distortion up to 16 KHz. I say "just a bit" because this level of distortion also is too low to hear any difference at all.
But if you must compare them with regards to distortion and noise specifically, my money is the OL DAC being the winner. The SDAC wins in the other measurements relatively speaking, but both PASS on all measurements and you'll only be able to tell which one is the better sounding DAC to your ears against your equipment chain by auditioning them.