Unlimited Portable Audio Power? | Astell&Kern KANN Ultra Review

Unlimited Portable Audio Power? | Astell&Kern KANN Ultra Review

While Astell&Kern is known for a high level of refinement in their luxurious digital audio players, their KANN series has always been more focused on raw power than refinement. With their latest round of players, Astell&Kern has continued to improve their user experience, especially making life easier for users who prefer apps over maintaining a music collection. KANN Ultra is the first to combine the KANN series raw power with the latest of the brand's UI innovations. Does Astell&Kern deliver a real upgrade to the unique, versatile experience that the KANN series has always provided?

Build and Design

KANN Ultra brings together design cues from past KANN DAPs.  The size and form factor harken back to the original KANN and KANN Cube, but other aspects of the design are closer to the more compact KANN Max. The larger size means it’s not as easy to pocket as KANN Max or Alpha, but the larger 5.5” screen improves the usability of the keyboard, and makes Ultra feel closer to a premium smartphone than previous entries in the series.

Astell&Kern KANN Ultra Review Body

The angular ridges and aluminum body provide a classic Astell&Kern feel, and the large volume wheel provides a striking visual accent. The wheel is oriented so that it’s facing out the back of the device, which can make it somewhat cumbersome to change the volume while the device is lying down, but the wheel itself is satisfying to use. The hardware play/pause, skip, and return buttons are also well constructed. One big change for KANN Ultra is that Astell&Kern has dropped the 2.5mm output, offering separated line and headphone outputs for 3.5mm and 4.4mm. Internally, A&K have engineered separation between the components to reduce the sort of noise and crosstalk that can be exacerbated by higher gain signal pathways.

Using KANN Ultra

KANN Ultra uses Astell&Kern’s Crimson UI, which is both an aesthetic and practical improvement over the previous A&K UI. Along with that, KANN Ultra’s Octa-core Processor is very fast. Maybe not iPhone 15 fast, but certainly plenty fast for music management, TIDAL, and YouTube. For the screen, UI, and performance KANN Ultra is in the top tier of DAPs alongside SP3000 and the iBasso DX320. Astell&Kern KANN Ultra Review Screen View

One bit of controversy at KANN Ultra’s launch revolved around exactly which version of Bluetooth the device was using, and how wireless performance would be. While we haven’t been able to run technical benchmarks, both the wireless networking and Bluetooth 5.3 implementation seem to be very good. We had very few issues connecting to the WiFi and roaming in a large space, with a large number of devices and connections. The WiFi connection remained strong even in some of the building’s typical dead zones, and Bluetooth sound quality was excellent while Bluetooth range seemed about average.

Astell&Kern estimates 11.5 hours of playback time, and that was consistent with my experience with the device. Using medium gain and moderate volume, while only using the screen as necessary, I got close to 11 hours of playback time before a full drain. High and Super gain will create a much higher level of battery drain, which came closer to 5-6 hours of playback for hard to drive over-ear headphones in our testing.

Among the notable features of KANN Ultra, are DAR (Digital Audio Remaster), Crossfeed, and the Pre-Line Out option. DAR is a sort of digital upscaler that adds an extra sense of separation and clarity to the music. Crossfeed gives you a number of options for blending a percentage of your left and right channels to either add a more speaker-like blended feeling, or  “correct” mixes that were made without headphones in mind. Pre-Line Out lets you control the specific voltage level being transmitted from the Line Out side, with Unbalanced/Balanced options ranging from 0.7V/1.4V to 2V/4V.

Astell&Kern KANN Ultra Review Input Output


KANN Ultra maintains the classic KANN sound, with a full-bodied, but largely neutral output. While it doesn’t have any strong emphasis or color in the tuning, KANN Ultra’s powerful dynamics and strong note weight make it a great pick for bassheads. The clear, full mids, and crisp treble help make up for any lost detail in bassy tunings, and the powerful, dynamic low-end lends speed and power to your headphones.

KANN Ultra’s imaging is also excellent, offering a soundstage with well defined width, depth, and height, along with a holographic sense of separation. It can’t reach the mesmerizing realism of SP3000, but combine KANN Ultra with headphones that provide strong imaging, like the Empire Ears Raven or HIFIMAN Arya, and you’ll be in for an immersive musical experience.

Astell&Kern KANN UltraOne of the best parts of KANN Max was how it was just as comfortable with highly sensitive IEMs as with hard to drive headphones. KANN Ultra follows suit and offers a dead silent, black background. Even on high gain, most IEMs didn’t pick up any hiss or noise. The over-ear headphone performance is equally strong. KANN Max only needed Super gain mode for HIFIMAN Susvara level challenges, and while it didn’t provide the full Susvara experience that a good desktop amp can, it would remain a good choice as a backup for quieter listening.

Comparison: iBasso DX320 ($1599), iFi Diablo 2 ($1299)

Core to KANN Ultra’s identity is its status as one of the best portable solutions for over-ear headphones, but how does that compare to other solutions for headphones on the go? On the one side, Diablo 2 is a portable DAC/Amp that aims at the status of the best portable solution for hard to drive headphones. On the other side, we have the iBasso DX320, which is a DAP with above average power, but not the sort of wattage that Diablo 2 and KANN Ultra put out. Is KANN Ultra powerful enough to stand with Diablo 2? Or maybe all this power doesn’t really make a difference. Is DX320’s above average – but not particularly impressive – output enough?

To test things out, I listened to a short playlist with the Thieaudio Monarch MK3, Campfire Audio Cascara, 64 Audio Volur, Meze Empyrean 2, HIFIMAN Arya Organic, and HIFIMAN Susvara on each device, and took some notes as to the performance and synergy with each one. We also listened to a number of other headphones and IEMs across the devices in a less scientific fashion.

Power Output

IEM Performance

Meze Empyrean 2 Performance

HIFIMAN Arya Organic Performance

HIFIMAN Susvara Performance

Astell&Kern KANN Ultra


Dead silent on low/medium. Noise only notable on High/Super with very sensitive IEMs

Needed 60-70% volume on Medium gain. Solid all around performance.

Nearly perfect performance at High gain and 80-100 volume.

80% volume was a comfortable level on Super gain. Need 90% for more punch, but had clipping above 90%.

iFi iDSD Diablo 2


Some noise at higher volumes, but the noise was manageable with Normal gain and iEMatch.

50% Volume on high gain was plenty, and Diablo 2’s aggressive highs nicely balance Empyrean 2’s warmth.

Effortless performance with 30-40% on “Nitro” or 60-70% on Turbo.

Best slam and strongest performance. 40-50% volume on Nitro gain was near perfect for me, but there was some clipping over 50%.

iBasso DX320


Excellent overall. Very low-noise, but small amounts of interference on Medium or High gain with sensitive IEMs.

66% Volume high gain was a good listening level, and DX320 has the smoothest overall sound.

Needed about 75% volume on high gain. Sounded good, but didn’t feel as dynamic as KANN Ultra or Diablo 2.

Barely loud enough even for relaxed listening. Very little bass slam at 95% on High gain.

Note: DX320 labels it’s gain modes as “Low, Medium, High.” KANN Ultra uses “Low, Medium, High, and Super.” Diablo is “Normal, Turbo, and Nitro.”

Astell&Kern KANN Ultra Review comparison DX320 and Diablo 2

DX320 was a good fit for a range of IEMs and easy-to-drive over-ear headphones, and a better fit if all you listen to are IEMs. With an Audio-Technica M50x or Sennheiser HD660 S2, DX320 didn’t seem to have any disadvantage, but with harder to drive planar magnetic headphones there was a sense that you just didn’t have enough power to get most of the headphones. At this point, Diablo 2 and KANN Ultra demonstrate a real advantage with headphones like Arya or Audeze LCD-2. While Diablo 2 had better performance than KANN Ultra with Susvara, it still didn’t feel like a 100% capable solution for those hardest to drive sets.

In short, if you want to listen to a range of over-ear headphones on the go, there is a clear advantage to high-powered devices like Diablo 2 or KANN Ultra over typical DAPs and portable DACs. However, no matter how much voltage you give them, portable solutions can’t provide the level of current the hardest to drive planar magnetic headphones demand off a battery, and desktop amplifiers remain the best way to get the best performance.

The Bottom Line

In terms of features and performance, KANN Ultra has an impressive list of bullet points. In terms of practicality, it provides an excellent all in one solution portable for over-ear headphones. The size and weight does limit its portability a bit, but as a total package, KANN Ultra offers a clear evolution in the KANN series, particularly by catching the user experience of this fan favorite line of powerhouse DAPs up with the rest of Astell&Kern’s lineup.