I think many assume that there is a DAC that fits all---100% transparent. No. And the reason is each and all DACs use a digital filter. That digital filter can never be 100% transparent like vinyl gear. This is the main consequence of using digital technology. At any price.
Therefore, every DAC introduces a tweak on the recording, it's just the gravity that's different with each DAC. That tweak is due to the DAC chip, implementation and the DAC filter used.
Now, assuming everything else equal, the most influential factor to the sound is the DAC filter. This is why every DAC using the same type of DAC filter has a similar sound quality/characteristic. In fact the most consistent influence in a DAC's sound characteristic is the DAC filter.
What many considers as the most transparent, objectively, is what's commonly known as the linear phase filter, which is used in our beloved ODAC.
But as in the case of anything digital, there's a trade-off, and, in the case of linear phase filter, that would be pre-ringing and post-ringing of certain frequencies especially in the uppermost frequencies. So even the linear phase would sound "digitally", though perfect and, in fact, the best, IMHO, in terms of transparency and, as I said, measurements.
So, if we use another filter that removes those pre-ringing and/or post-ringing, there's nothing wrong with it as in fact we're trying to even improve the close perfect, objectively, linear phase. But as there's trade-off in anything digital, again, 100% transparent isn't possible.
So using another digital filter to remove/reduce those pre and post ringings is still not 100% transparent, BUT could be closer to your subjective measurements based on the music you listen to and prefer. This preference is different in every person. So different filters, IMHO, should be interchangeable in a DAC.
Personally, I prefer the minimum phase filter, because it removes the pre-ringing, which IMHO is the main reason for that "digitally" sound. This filter doesn't remove post-ringing, which for me is alright because real live analogue sound has post-ringing as well (think echoes, reverberations, and the like). However, as said, there's a trade-off, and in the case of minimum phase filter, that would be time domain differences/delays and slight-roll-off of the upper frequencies. In my ears, these trade-off doesn't make the sound "digitally", it just makes the sound a tiny bit more "scattered", for lack of better term. On the lower registers/frequencies, this makes the bass bit more/bigger. On the upper frequencies, I can't discern it much, and I think that's because of the un-corrected and existing post-ringing, which offsets the high frequency roll-off. IMHO, this post-ringing gives out a better soundstage.
So I sincerely suggest a DAC with good DAC chip, good implementation and interchangeable multiple filters that preferably includes linear and minimum phase filters.
So far i used it with my HD600 and DT990 Pros (250omhs) and i can say it made both headphones sound more natural (which i didn't expect with the DT990s) and more detailed. However i didn't hear a HUGE difference or that the headphones NEED the amplification since i don't believe it's a night/day difference.
) . But now with the ALC 1150 their is more and more , what you can say an headphone amp for the onboard audio chip . He has to check what is the audio chip and if their is an headphone amp .
