The Unpredictability of Predictability.

PROs: 4 separate AK4191EQ filters/modulators and 4 separate AK4499EX DACs, 904L stainless steel solid build chassis, hi-res 6” display, Snapdragon 6125 SoC w/8GB DDR4 RAM and 256GB internal storage, 3.5mm and 4.4mm PO/LO, LDAC Bluetooth (both Tx and Rx), natural resolving tonality with super black background and big soundstage expansion, Advanced DAR, High Driving Mode, super clean Line Out, full access to Google Play Store, ROON support.

CONs: price, weight, additional battery drain when DAR/HDM is enabled.

The product was provided to me on long-term loan for review purposes in exchange for my honest opinion.

The manufacturer’s website: Astell&Kern.  It can be purchased from authorized retailers, such as Musicteck.

*** UPDATE *** The latest A&K firmware 1.02 update for the SP4000 has resolved the notification touch area swiping issue with the DAP inside the leather case.  No more issues related to that.

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Intro.

Fans of A&K DAPs are well aware of how their flagship releases coincide with being one of the first in the implementation of the latest AKM DACs, just like SP1000 with AK4497, SP2000 with AK4499, and SP3000 with AK4919EQ/AK4499EX.  I do have to admit, there is predictability to many A&K flagship releases, including SP2000T and SP3000T dual tonality with solid state and Tube modes, and, hopefully, continuation of SP1000M and SP3000M miniaturization in between main SP-series models.  But this predictability came to a halt when many audiophiles were expecting the next A&K flagship DAP release, while AKM hasn’t announced any new DAC chips.  What do you do then?  Expect the unpredictable when a manufacturer gets creative with DACs, they have access to, taking it to the next level of fine-tuning.

When SP4000 (SP4k) was announced, on paper, it looked more than just finetuning with four pairs of AK4919EQ/AK4499EX combo, also including a bigger high-res display (6”), implementation of a new Advanced DAR remastering algorithm, a new High Driving Mode (HDM) by doubling opamps in the amplifier circuit, some other tech inherited from smartphone circuit board design, and one truly unpredictable surprise of lifting the app limitation and allowing the access to Google Play Store to download and install many other popular apps.  I was personally looking forward to the finetuning part of this DAP because, at the end of the day, it is all about the sound and the pair-up synergy of the source with my earphones and headphones.  Here is what I found after spending the last few weeks with the latest A&K flagship release, their SP4000 DAP.

Unboxing and Accessories.

Any die-hard fan of A&K DAPs would know that the SP-series unboxing experience starts with the opening of a wooden storage box.  That’s how it was with SP1000, SP2000, SP2000T, SP3000, SP3000T, SP3000M, and… not anymore with SP4000.  It was a bit of a shock when I received this HUGE packaging box with SP4k, removed an all-black sleeve with an A&K logo, and found a heavy-duty cardboard “shoe” box inside.  Opening that box revealed an elegant, jewelry-style storage box, covered in a fine-textured vinyl.  It didn’t feel like a leather box, but had a very distinct look nonetheless.  Not sure how practical it will be after you start using SP4k, but it was something different.

As you release the buckle latch and flip it open, you’ll find three sections: one large built into the cover, where the included leather case is located, along with a warranty card, a quick start guide, and several screen protectors for the front and back of the DAP, including spares.  The other side of the box featured two sections: one with SP4k DAP, a high-quality USB-C to USB-C high-speed cable for charging, data transfer, and USB DAC functionality, and another traditional small cardboard card with a pocket and microSD card slot cover (plastic dummy microSD card).

In the adjacent section, I saw “A&ultima SP4000 – A Journey of Excellence” card, which I picked up to find a foam insert with a serial number card inside, and underneath – another surprise: a small black leather bag with a flip-top cover. At that point, I already had SP4k inside its leather case, so naturally, I stuffed the whole thing into that other leather bag. It did fit, although it was a bit tight, and I could barely secure the flap cover under the exterior strap.  I assumed it was meant to be a carry-on bag for SP4k inside its case, to protect and cover the display, and to carry it by attaching a lanyard through the metal ring on the back.  Later, it was clarified that this storage case was meant to be for other accessories, such as IEMs with cables, a charging cable, and anything else you can think of.  As A&K is a rather traditional company, I find it peculiar when they change something, or at least, try to.  This carry-on small bag was a good attempt, though I wish it had a middle partition to separate different items instead of everything being mixed in one open area.  Also, including a lanyard would have been a good idea, too.

The included premium Leather Case is crafted from soft, shrunken calf leather by Perlinger, Germany.  According to the A&K, it is processed using the chrome tanning method to preserve its natural texture, and shrunk using special agents instead of heat to retain its organic grain and wrinkles.  Also, there is a whole science of the dyeing process, adding proprietary pigments through advanced anti-aging treatment to achieve deep colors that won’t fade over time.  The case doesn’t hide but instead highlights the details of the SP4k design.  At the top, you will find a generous opening for 3.5mm/4.4mm ports and a button-lock switch.  The right side has an easy-to-access opening for the volume wheel.  The bottom covers the microSD card port and gives you access to the USB-C port.  You slide in the DAP from the left side, securing it with a flap that tucks in and covers all three playback control buttons with an easy-to-feel indentation.

Also, it has become a tradition that whenever a new SP-series DAP is released, Dignis typically comes up with their custom version, something they have already started teasing on social media as I was writing this review.

Design.

I recall writing in my SP3k review that it was the largest DAP in the A&K SP-series.  SP3kT remained close to it, and SP3kM shrank in size and weight.  SP4k went the opposite way and now holds the crown for the biggest and heaviest in their flagship series, measuring 149.8mm x 85mm x 19.5mm, and weighing 615g.  With a bigger 6” display, everything scaled up in size and corresponding weight, especially considering the use of Stainless Steel 904L body material available in black and silver finishes.  Plus, the battery capacity went up.

SP4000 vs SP3000M

The design still focuses on a new stunning 6″ HD touchscreen at the front. The front view of the DAP remains asymmetric, a signature A&K design look, due to uneven sculpted bevel sides, including a slightly bulging area around playback buttons on the left and a crown-patterned volume wheel on the right with a more open side-guard cutout area around it. The volume wheel functions as a power button, requiring a long press to turn the device on or off, with a confirmation to shut down or a short press to toggle the screen on or off.  As always, I prefer double-tap to wake up the screen, which is also available as an option in SP4k.

The volume wheel features a unique crown pattern. It is easy to turn with a thumb, though it’s not loose and has some resistance, with a click action felt with every 150-volume step rotation.  A multi-function LED behind the wheel is also implemented to indicate charging status or bit depth, depending on the source file (16bit – red, 24bit – green, 32bit – orange, DSD – purple, DAR enabled – blue). LED light could be disabled in Settings. The design of the volume wheel has a detailed, unique crown pattern, typical of a wristwatch, which varies between different A&K models.

On the left side, you have Play/Pause and Skip controls, three identical small rectangular buttons located in the upper part of the left side. They do have a nice tactile response and are spaced evenly with enough room in between to avoid pressing an adjacent button by mistake. The top of the DAP has access to a 3.5mm single-ended phone output port, which is also used for Line Out and Optical Out. Next to it, you have 4.4mm balanced phone ports that could also be configured for the corresponding Line Out.  The “legacy” 2.5mm balanced output is gone, just like in SP3kM.  2.5mm is an old standard, and with 4.4mm in SP4k implementing GND connection, unlike some other manufacturers, you no longer need ground adapters with bridging of 2.5mm/3.5mm ports.

One new addition to the design is a Button-Lock switch at the top to the right.  I have to say, when I first got SP4k out of the box, I was a bit confused, considering my previous extensive use of SP3kT and SP3kM, both of which had a separate power button in that spot, pressing it to turn on the DAP.  Even after realizing it was a slide switch to enable the button lock (locking the volume and playback buttons), I still needed a few more brain cycles to adjust to the volume wheel being the combined power button.

At the bottom, similar to the SP3k/T/M, the SP4k has a USB-C port, used for charging (including Fast Charging), data transfer, USB DAC connection, and USB OTG external device connection for digital audio out.  Also, to the right of the USB-C port, you will find a spring-loaded microSD card slot, with A&K acknowledging support up to 1.5TB.  The back of the DAP also has a typical A&K asymmetric design with an extra cutout around the volume wheel.  Overall, the lines of the SP4k design are similar to those of SP3k models, being less aggressive and classier. However, SP4k stands out with more protruding and deeper cutout guards on the side around the volume wheel.

Page 2 – Under the hood, and GUI.
Page 3 – Sound Analysis, Comparison.
Page 4 – Pair up, Wired/wireless connections, and Conclusion.