NEO iDSD 3

This is my 3rd Amp after the Hifiman Serenade and Mayflower Arc MK2. Right off the bat, let’s just be clear that this is obviously in a different price tier and league, far above the Arc MK2, so I won’t compare it too much to that. But it will be used as a reference point, because I don’t have a massive collection of amps to do an extremely in depth comparison. With that being said, this is all my subjective opinion. I like my audio a certain way: Leaning musical, without becoming muddy or soupy. The iDSD3 accomplishes that pretty much perfectly. I’ve owned “neutral/reference/monitor” type headphones before. Not my flavor, so I go out of my way to avoid amps/DACs with that description. A lot of people in the “Audiophile” community, particularly reddit snobs, will tell you that an Amp/Dac is “only like 2% of the sound. The other 98% is the headphones.” Not true in my subjective experience. The Amp/Dac can play a significant role, as long as you’re not comparing very transparent and neutral units to each other. The iDSD3 and Serenade are both “flavored” to an extent, so they definitely provide a unique sound signature.
Using the same exact headphones (HE1000 Stealth, Arya Organic, Edition XS, HD660S2, V-Moda Crossfade), there is a distinct difference in the sound signature between the Serenade, Arc MK2, and iDSD3.
The Arc MK2 is the budget/gaming oriented amp in this case. It’s relatively neutral and competent, with the option of adding DSP Flavor. Adequate for powering the majority of headphones, but not on the same level as the other two. It just gets the job done nicely, and has a mic input for gaming. Good unit.
The Serenade is a very flavored unit, that leans far into the musical/rich/lush side, but sacrifices detail, edge, and separation to pay for it. It seems evident that Hifiman made it to balance out their harsher, more technical headphones, like the Arya Stealth, HE1000SE, and HE1000 Stealth. When paired with the HE1000 Stealth, which is a very precise and detailed pair of cans, the Serenade balances out beautifully, like Yin and Yang. Excellent detail, separation, and stage. While Simultaneously providing rich, layered, and heavy notes. However, when paired with the Arya Organic or HD660S2, the audio becomes muddy/soupy and loses detail, while doubling down on richness. The Arya Organic is tuned to favor musicality, without giving up technicality, out of the box. So it can pair well with Neutral or musical LEANING amps. But not “richness machines” like the Serenade. There lies the issue. Unless you have the proper synergy regarding the headphone pairing, or you just heavily favor musicality over technicality, the Serenade will not fit the bill for you.
The iDSD3 on the other hand, retains superb detail, layering, and definition; without overdosing on richness the way the Serenade does when paired with like-minded musically tuned headphones. The iDSD3 adds just the right amount of “musical” to abstain from sounding clinical, which allows it to pair extremely well with all of my current headphones. If you decide to pick this up, and prefer musical AND detailed audio, I don’t think there’s another All-in-One Amp+Dac in this price range that balances those two aspects quite as well. The Arya Organic absolutely shines on the iDSD3, and that pairing is currently my daily driver.
So from the sonic side, it’s perfect for me.

Regarding features: it has Xbass, Presence, and X Space. When I use my HD660S2, the xSpace feature works nicely, so that’s definitely a thing you would use for small-stage mid focused headphones. I would not turn it on with large-stage planars, because it thins out the mids too much. Moving on, xBass is exactly what it sounds like. It adds bass. If you own a pair of headphones like the Edition XS, that have lots of Air, Separation, and detail; but very thin or flat mids, this feature works wonderfully to add some meat on the bone.
None of my current headphones really need the “Presence” feature, but it helps when watching shows or movies where the audio mixing drowns out dialogue. So Presence can work as an excellent dialogue booster. Regarding K2 and K2HD, I don’t have the “expert-level audio listening” powers to really tell the difference in audio quality from when K2 is on or off. But if you want it, it’s there. Theres also lots of filter options I don’t really want to get into, and 4 gain settings. No shortage of sound shaping and customizability features here. But also not an extremely technical PEQ suite like the Fiio K17 has, if you’re into that. I would say for most people, the options here are plenty to shape the sound without falling into the EQ graph rabbit hole. Thats really the strength of the iDSD3. The default sound signature pairs well with most headphones as it is, and the sound shaping features allow you to compensate for any weaknesses your headphones may have out of the box.
I should also add that the transparency is excellent at any gain level.