The ALO Audio Reference8 IEM cable (featured above) has a profound effect on the U12’s only weakness: treble. It transforms the U12 into a clearer, airier transducer, with genuine shimmer to those high frequencies. You still get lots of warmth and lows, but now there’s light in the mix, brining out greater detail and definition. Ref8 is currently the only cable I’ll use for the U12. My love for this IEM has increased tenfold.
It is said the whole ADEL & APEX line was tuned for high-impedance stage equipment, and any audiophile gear you may have, is very likely going to make these sound overly warm. 64Audio recommends Impedance Adapters to compensate. I’ve seen the measurements, with adapter and without; Head-Fi member Brooko performed some thorough tests and shared his graphs. In my eyes, it looks as though its main effect is to lower the bass by a hefty margin. The treble is little changed, however much your perception of it may alter.
Because of this, I have no intention of going the Impedance Adapter route. The bass of U12 w/B1 or M15 is utterly splendid. And the Ref8 helps with the highs. No need for impedance adapters.
Every DAC or DAP I own outputs 2 Ohms or less. Even my desktop DAC&Amp, the Audio-GD NFB-28 keeps things at 1 Ohm, no matter the gain setting. All of my equipment sounds fantastic with the U12.
The Cayin i5 is to the U12 as gasoline is to fire. Huge bass and warmth pumping into an IEM tuned for huge bass and warmth. It can be a bit too much. However, with recent firmware updates, I’ve found the i5 more balanced than it used to be, and the U12 doesn’t sound so veiled. This may not be my favorite pairing, but I can’t deny the sheer musicality it produces.
One of the best things into which you can plug this IEM is the Opus#1 by Audio-Opus/theBit. This player has strong treble presence, without being bright or harsh. It is neutral done right. Highly dynamic, punching hard in the low-end, and rendering phenomenal clarity throughout the mids. Details are brought out in superb resolution. It gives the U12 a kick in every area it needs a little help in, without diminishing any of its strengths.
The NFB-28>U12 blew my hair back. Seldom do I listen to IEMs from my desktop DAC, but now I question that rationale. It sounded beyond good. The detail, the soundstage, the level of refinement, this setup put my Astell&Kern to shame.
For over a year now, 90% of my listening is done via the Astell&Kern AK120II. And most of that transpires at work. Even though I got this DAP for a hard bargain, it’s still one of the most expensive things I own. I needed a DAP which left me wanting for nothing, one whose audio quality stood above the reproach of my increasingly critical ears. Let me assure you, I bought wisely. This player is the very definition of smooth, with its neutral-warm signature and rich timbre. There are no harsh sonic edges, or symptoms of digititis. Its soundstage is the biggest I’ve found in a DAP. In other words, the AK120II perfectly illustrates the virtues of the U12. If I can’t carry the NFB-28 in my pocket, at least I have the next best thing.
A few months ago the AK120II was usurped by the Opus#2. Not only is the Opus a step up from the AK, but it’s also a better pairing for the likes of the U12. While the Opus#2 is also a neutral-warm signature, it delivers more energy and dynamism. Its treble has greater presence, and casts extra light onto the arena. The soundstage is so grand and articulated, with a level of refinement which dwarfs other mobile players. I’ve not heard any DAP sound this realistic, this organic and analogue. The truest companion of all to 64Audio’s U12.
I must admit, I have found it difficult to go back to traditional IEMs after this. The ADEL and APEX technology makes too great a difference. It’s difficult to say if either one accomplishes the health goals Ambrose of Asius originally set out for, but on a strictly sound and “feel” level, something fabulous is happening here. Ambrose is off doing tremendous works with Empire Ears, and 64Audio is going strong with APEX. The audiophile field is rife with exciting shit, and I’m eager to see what becomes of it all.
In the meanwhile, I have my replacement for Angie. And much, much more. I seem to have stumbled onto an IEM that lays waste to every expectation I harbored. The 64Audio U12 is god-tier, and everything I look for in life.