Before doing any critical sound analysis, I had E02 w/N6ii on burn in for about 4-5 days playing various tracks in the loop. Afterwards, for critical listening I used 64 Audio U18t to analyze and compare between A01, T01, E01, and E02 modules, using my usual test tracks, such as Agnes Obel “The curse”, Sandro Cavazza “So much better” (Avicii remix), C-Bool “Never go away”, Ed Sheeran “Shape of you”, Alan Walker “Darkside”, Galantis “Hunter”, Iggy Azalea “Black widow”, Indila “Boite en argent”, Counting Crows “Big yellow taxi”, David Elias “Vision of her”, and Michael Jackson “Dirty Diana”.
In my opinion, the best way to understand and to describe the tonality of N6ii modules is by comparison of one to the others. And while it is convenient to have access to two DAPs for a true A/B comparison, I was actually able to do a module hot-swap. Cayin doesn’t recommend swapping modules while powered up, but it works without a problem and the DAP even remembers the last volume setting for that specific module. It took me literally a second or two to swap between modules when doing the comparison. But as a DISCLAIMER, do it at your own risk.
E02 vs E01 (AB) – E02 soundstage is a touch wider, and while I was impressed with soundstage expansion of single ended E01 output, E02 spreads L/R a little bit further apart. Bass (E02) has a bit more impact and more rumble with a velvety texture, mids have a little more body especially in lower mids while E01 mids sound more transparent and E01 treble is just a little bit smoother, making E02 signature more organic, placing E02 performance between E01 (A) and E01 (AB), though being closer to E01 (AB). But in general, E02 is not too far off from E01. Also, despite a rated difference in output power, regardless of IEMs or headphones, I hear a difference of about 5-6 volume clicks.
E02 vs T01 – T01 soundstage is a little bit wider, perhaps due to a brighter tonality with airier treble. T01 bass is faster and tighter, with shorter decay, mids are brighter, more revealing and micro-detailed while E02 mids are more natural and smoother, and have more body. The treble of T01 is crisper and brighter. The preference here will depend on the signature of IEMs/headphones and how it pairs up with either of the modules.
E02 vs A01 – E02 soundstage is a little wider. Overall tonality is similar, but there are some differences I’m picking up. E02 bass has more rumble and more analog texture. Mids are similarly smooth, but E02 has more organic layered natural texture. I went back and forth many times comparing these, focusing specifically on mids, and that texture and better layering and separation is what makes E02 stand out, especially when it comes to vocals. Also, E02 treble has a little more sparkle and airiness. Overall, E02 sounds like it has more analog texture, better layering, and improved sound dynamics in this comparison.
For consistency, all earphones and headphones were tested in Med gain. Volume is noted with “v”, and please keep in mind that max volume is at 100.
64 Audio U18t (v28) – very natural detailed tonality with an expanded wide soundstage, balanced signature, great bass impact with deeper sub-bass rumble, nicely layered natural mids/vocals, natural non-fatigue treble sparkle. The sound was very natural and dynamic, and still quite resolving. Very mild waterfall hissing when idling (volume 0) or in quiet instrumental song passages, hardly noticeable at normal listening level.
Campfire Audio Solaris OG (v18) – very wide soundstage expansion, natural detailed tonality with a balanced signature, impressive deep bass impact, natural detailed mids/vocals, non-fatigue natural treble sparkle. The sound is very organic and detailed. There is a more noticeable waterfall hissing when idling (volume 0) or in quieter instrumental song passages. But not as noticeable at normal listening level or when I’m playing my usual selection of mainstream or EDM tracks.
Meze Audio RAI Penta (v25) – wide soundstage expansion, balanced signature, deep-sub-bass rumble, natural detailed mids/vocals, revealing yet still with organic texture. Well controlled treble with a little extra natural sparkle. Very good natural dynamic pair up. I hear a bit of mild waterfall hissing when idling or in quiet instrumental song passages, but hardly noticeable at normal listening level.
Empire Ears Legend X (v30) – wide soundstage expansion, typical L-shaped signature with a VERY analog sounding bass (your typical pumping bass woofers). But regardless of the signature, mids/vocals still have a good focus with a natural organic detailed tonality, and treble is not shining away from well controlled sparkle to balance the tonality. These are dead quiet.
VE Sun Dice (v48) – great pair up with these 180ohm earbuds! Open, wide soundstage expansion, balanced signature with a very natural and detailed tonality. Bass has a nice analog punch, not exaggerated but well balanced with mids and treble, regardless that this is actually earbuds that sitting on top of ears in concha area. Mids/vocals are very natural and detailed, again quite a surprising level of clarity from earbuds. Treble is crisp, not fatigue and very natural. The pair up was very enjoyable!
Sennheiser IE800s (v37) – wide soundstage expansion, balanced signature with a little more emphasis on mids, deep rounded analog textured bass, very clear and a little more revealing mids/vocals which still sound quite natural, crisp well controlled airy treble. Dead quiet.
FirAudio M5 (v30) – wide soundstage, balanced signature, deep articulate bass impact with a textured rumble, clear detailed organic mids/vocals (more natural than w/EO1), crisp controlled treble. The bass impact of M5 in this pair up is probably among the best I heard and at the same time not as boosted as in some other pair ups, making overall signature nicely balanced. Faint hissing at low volume, but not at normal listening level.
Final Audio A8000 (v37) – very interesting pair up because with many other sources A8k can sound more mid-forward due to neutral bass impact and more emphasis in upper mids. With E02 (similar to E01), besides a very wide soundstage expansion, the bass is very deep, fast, and has more impact, bringing more balance to the signature, actually resulting in a more v-shaped signature since treble is also very crisp, well pronounced, and with a nice level of airiness. Not as much sibilance in this pair up. Mids/vocals sounds natural and micro-detailed at the same time, with a little less body in lower mids and a little more emphasis in upper mids.
Beyerdynamic T5p 2nd (v39) – wide soundstage expansion, nicely balanced natural tonality with more revealing retrieval of details. Bass has a deep analog extension with a faster mid-bass punch. Mids are natural, layered, and still with retrieval of details on micro-detail level. Treble has well controlled sparkle and airiness, crisp but in a more natural non-fatigue way. In this pair up E02 does more analog justice to T5p2 low end in comparison to E01.
Meze Audio Empyrean (v41) – very wide and open soundstage expansion. The tonality is very natural yet quite detailed. The sound is very dynamic, layered, balanced. Deep analog bass extension with a powerful impact, natural detailed mids/vocals, and natural well-defined treble sparkle. In comparison to E01, here you have more weight in low end and more natural fuller-body mids, and overall, it feels like E02 makes Empyrean sound more analog.
E02 module makes a worthy addition if you already have T01 or thinking about upgrading from A01. But I know for some the question will be if they should stick with E01 or go for E02. If you are choosing between E01 or E02, I recommend E02 due to its versality and overall a better value. You are getting balanced headphone output and can still use it with single ended headphones if you get the adapter. Plus, you get a clean balanced (and singled ended) Line Out to use N6ii with external amplifier. And even though E01 has a little blacker background, you can get E02 to the same level with single ended adapter.
I personally see a lot of advantages in E02 design. But at the same time, if you are happy with E01, enjoying switching between Class A and Class AB amp mode, don’t mind SE output, and don’t have a need for LO, there is no reason to lose a sleep over this, and you should continue to enjoy E01. It is good to have a choice, and that’s what N6ii modular design is about. And on top of that, when you are buying a new N6ii you have a choice which module you can get, and some retailers, like Musicteck, even offer bundles with various amp combinations to save more money.