For DACs, I've only owned my FiiO K9 Pro ESS, but for amps can at least say that at an audio show when comparing the Eleven Audio Broadway (smaller) and Formula S (bigger) amps (and before that a small DAP I think with a mini tube, but rather coarse volume control) which each had a different Abyss Diana MR hooked up, but the same source, after even a cursory
volume matching (which is oh-so important) between the two amps which were both plenty adequate to drive the Diana MR
loud enough, as far as I could tell, there was nothing to prefer between the amps, each presenting a similar if not identical tonality and largely the same qualities of details and "bigness", such to be expected
if they all indeed measured as having the same largely flat frequency response.
With audio, I would rather start with the cheapest possible solutions before "escalating", so trying out EQ first,
then maybe earpads, though even before earpads, if this "darkness" you are hearing is in fact rather a case of the amp not driving the headphones
loud enough (does it stay dark when you increase the volume (make sure your digital source's volume controls are also maxed), or is your amp already on max volume?), then there is objectively no workaround but to try switching from an unbalanced cable to a balanced cable if the amp supports it (it simply doubles the voltage output, any other effects likely being caused by lack of volume matching), else acquire a more powerful amp. Anyways, at least per
https://www.audiosciencereview.com/...hiit-asgard-3-headphone-amp-dac-review.14393/, it is certainly exquisitely neutral, and the headphone output distortion performance is excellent, so I wouldn't expect
it to be the cause of the darkness you are perceiving unless it were simply failing to drive the headphones loud enough. As for earpads, which measurably can cause changes in frequency, unless you are adamantly avoiding EQ or are looking for improved comfort, I would rather use a free option like EQ to change my headphones' tonality.
As for
EQ recommendations provided that the issue doesn't have to do with amp power, then if your Arya is one of the models predating the Arya Organic (I doubt it is the Organic you are finding "dark"), to address "mud", if that's what you meant by "darkness", if you can get your hands on parametric EQ (PEQ) software, I would place a -2.5 dB peaking filter with a Q factor of 1 centered at 270 Hz; the switch from the Arya Stealth to the Organic theoretically does something similar, but with added bass and upper treble. Then, if you want a bit more clarity or find the midrange a bit "dull", I would add a 4 dB peaking filter with a Q factor of 2 centered at 1.7 kHz to fill the "HiFiMan dip". Then you may want to add a -3 dB peaking filter with a Q factor of 5 centered at 3.15 kHz to smoothen that peak. I am basically describing how to EQ the Arya Stealth toward the headphones.com's Harman target based on the graph below:
I can say for me that when I first turned on the EQ profile I produced from this graph, the jump in clarity was truly like lifting a veil. And if you are familiar with
my posts (post #4,665), you would know that the rabbit hole of EQ for achieving yet greater levels of clarity or transparency only continues.
Finally, if the "darkness" you described was rather from a lack of treble, you can apply a high-shelf filter centered between 7 kHz or 10 kHz and play with the gain and Q factor to your preference. A general "ear gain" peaking filter with a Q factor of 1 centered at 3 kHz can also be used to play with how much upper midrange and lower treble (the region naturally amplified by your ears) you want.
Note that whenever you add a
positive gain PEQ (or graphic EQ) filter, you must also apply a "digital pre-amp" to prevent that EQ from causing digital clipping. Technically speaking, both digital and analog volume controls are merely performing an
attenuation of the signal from reaching its maximum value. With your amp's volume knob turned to the max, it is simply passing in the DAC's full output, whereby the amp will only clip if the DAC is capable of outputting voltages beyond the amp's nominal input range. Likewise, the DAC will only clip if its digital input was clipped in the sense of the signal being boosted beyond the maximum values for digitally representing the signal's loudness. So if you are boosting by 5 dB, you should apply a digital pre-amp of -5 dB or more; on Equalizer APO, you would check that the "peak gain" on the lower left is zero or less. This does require you to run your amp at a higher volume or gain setting or gain, though.