Source Pair up.

I tried my Samsung Galaxy S25, iPhone XS Max, SP4000, LPGT, R6 Pro Max, and N6iii as digital sources driving the A100, and found hardly any noticeable difference in sound quality between them.

There were also no issues using A100 as a USB DAC with my aging ThinkPad T480S Win10Pro laptop; it was recognized right away, no drivers were required, and it sounded as good as with other mobile sources.

To my surprise, the only device I wasn’t able to use as a digital source with A100 was the P6 Pro.

IEMs/Headphones Pair up.

Here is how the A100 pairs with various IEMs and headphones.  All were connected to the 4.4mm BAL output.  Also, HG – high gain, LG – low gain.

Headphones

Audio-Technica ATH-R70x – These 470-ohm open-back low-sensitivity headphones are generally not easy to drive, but I had no issues with the A100.  Can’t tell you at what volume level, but there was still plenty of margin left.  I preferred the HG boost in driving R70x with A100, because in LG, the bass sounded soft, pulled back, while HG brought the bass back alive.  It wasn’t just the loudness of the sound, because I tried adjusting the volume, but couldn’t get the same effect in LG.  Switching to HG is what pushed R70x performance to its full potential.  The soundstage perception was wide, expanding even wider in HG.  The sound signature is balanced, with a natural, resolving tonality that leans slightly more revealing up top.  The bass performance is quite good, emphasizing a tight, punchy, fast mid-bass with a textured sub-bass rumble underneath.  Mids are neutral, natural, quite resolving, very detailed, without any added thickness.  Treble remained airy, crisp, and detailed without sounding harsh or fatigued.  Overall, to my surprise, R70x sounded a little more revealing than usual, but it wasn’t too bright or harsh.  Instead, it was presented in a less colorful and more resolving manner, which I enjoyed.

MEZE Audio Empyrean – I also preferred HG here, which gave the Empyrean headphones more authority in bass and improved the retrieval of details in mids.  The soundstage width was a definite surprise, as Empyrean typically has an average width with many sources. Still, here it stretched out more from left to right, creating a more spherically shaped soundstage with nearly holographic imaging.  The sound signature leans towards being balanced, but the tonality was more neutrally revealing, very detailed, and airy, with a slightly brighter upper range. The bass has a deeper sub-bass rumble with strong, punchy mid-bass that easily cuts through the mix. The mids have more transparency, improved detail retrieval, and increased clarity and resolution.  The layering of the sounds was impressive, considering that with some of the sources, Empyrean could sound denser.  Treble was crisp and airy, nicely extended, well controlled, but a bit more on a revealing side, which contributed to the improvement in detail retrieval and layering in mids.  Empyrean planar drivers benefit from more current, and A100 was able to deliver it, driving these cans with full authority, making them sound more resolving and micro-detailed.

IEMs

The original sound analysis above was based on testing the Aroma Jewel with A100.  Here is how other IEMs pair up and sound with A100.

FirAudio RN6 – I hear a big soundstage expansion, spherically shaped and expanded in all three directions, while the imaging was good, but leaning more toward the center.  The sound signature of the RN6 remained L-shaped, emphasizing more power and weight on the RN6 kinetic driver, producing a bass reminiscent of powerful floor-standing speakers.  Both a deep sub-bass rumble and a strong mid-bass punch are scaled up, driving its L-shaped signature, but they are not overpowering mids/vocals.  Bass has decent control, and the “magic” of A100 dynamic expansion kept the vocals’ presence up front without hiding behind the bass.  The bass is still dominating, but it doesn’t overpower or steal the focus away from the RN6 sound tuning.  Mids sound clear, detailed, natural, with a tasteful amount of texture and smoothness, and still quite resolving.  The treble was clear, detailed, with a moderate amount of crunch and airiness; I don’t find it being rolled off, but it does sound more natural.  What impressed me the most in this pair-up was the powerful energy of the scaled-up bass, which didn’t overwhelm the clarity, resolution, and retrieval of details in upper frequencies.

Elysian Acoustic Annihilator 23 – I noticed an expanded soundstage, spherically spaced and spreading evenly in all three directions. The imaging was also approaching a holographic level.  The Anni sounds mildly U-shaped with A100, having greater emphasis on sub-bass and upper mids/treble.  The bass impact here is very impressive, and even though sub-bass rumble scales up relative to mid-bass, the mid-bass came through with a nice, tight, and well-controlled punch.  Mids sound more neutral and transparent, with less coloring, yet they remain smooth and detailed, though their presentation is pulled slightly back.  The treble was crystal-clear, extended, airy, with a non-fatiguing crunch.  Anni is harder to drive IEMs, so I switched to HG for a second to see if I’d hear any improvement in the sound.  But in HG, the treble became crisper and a bit too energetic for my taste, so I switched it back to LG.

Forte Ears Macbeth – I hear a big, expanded soundstage with holographic imaging.  The sound signature is balanced, with a natural tonality in the mids and a slightly more revealing and crisper treble, all without being harsh.  The bass performance here is very powerful, making you forget that you are listening to a BA driver because it sounds like a DD driver’s performance.  The sub-bass rumble is textured and elevated, the mid-bass impact is scaled up, tight, fast, and punchy.  The mids don’t have a lot of coloring, but they do sound natural, smooth, and quite resolving, with a slightly forward presentation.  Treble is crisp, airy, extended, and a bit more energetic, which can cross a tolerance threshold in HG, but remains under control in a regular gain.  If you want to keep Macbeth’s treble under control, A100 in LG would be a better choice.

Conclusion.

Perhaps feeling jaded after testing and reviewing numerous audio sources, I was initially underwhelmed with the A100.  From an operational perspective, A100 was rather minimalistic compared to other dongles, lacking an LCD to display playback file resolution, volume level, or to access and change settings, and not having app support.  But it makes up for it in a big way when it comes to the sound, transforming your smartphone into a high-end DAP, which is why I find its pricing to be reasonable, even though it costs more than an average USB DAC dongle.  It is bigger than a traditional dongle, but it is slim, has a solid build, attaches magnetically, and stays securely attached. It also features a built-in battery that offloads the drain of your smartphone, offering an impressive playback time.  The output is also impressive, offering both high power and high current to drive anything from demanding loads to sensitive IEMs with a pitch-black background.

The sound tuning and technical performance make A100 stand out, having a big, expanded soundstage with holographic imaging, and being a neutral, resolving source that improved the tuning of my earphones and headphones by enhancing the low end with a textured, punchy, articulate bass, making mids more natural and layered, and giving the top end a slightly more revealing, non-fatigued, hi-res crunch.  The key here was the enhancements in tuning rather than a boost in frequencies.  The same goes for its technical performance enhancement, which in some way reminded me of what I heard from Brise and Mass-Kobo when I had their portable amps on loan for review.  I’m not suggesting that the A100 DAC/amp will sound just like Watatsumi paired up with an ESS-DAC source.  But the enhancement in A100 technical performance reminded me a bit of those Japanese portable amps that focus more on technicality rather than musicality.

Now, I’m very curious to see what else NiPO is going to surprise us with next.