A Tubey Goodness!

PROS: a dual amp design (OP/Tube) with a triple output mode (OP/Hybrid/Tube) offering a sound tuning variation of natural resolving tonality, 2x AK4191EQ/AK4499EX pairs, 2x Raytheon JAN6418 vac tubes, solid build 316L stainless steel chassis, hi-res 5.5” display, Snapdragon 665 SoC, updated user interface, 2.5mm/3.5mm/4.4mm PO and LO, DSD512, LDAC Bluetooth (Tx and Rx).

CONS: weight, price, waterfall hissing with sensitive IEMs in tube modes.

The product was loaned to me for review purposes in exchange for my honest opinion.

Manufacturer website: Astell & Kern.  Available for sale directly or from authorized online retailers like Musicteck and Bloom Audio.

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Intro.

As I already mentioned in the SP3000 review, based on my observation the Astell & Kern flagship releases are usually aligned with the announcements of new AKM DACs.  It happened with SP1000 and AK4497, SP2000 and AK4999, and SP3000 and AK4499EX/AK4191EQ.  But if you are either a loyal A&K customer or in the market for a new DAP, you don’t have to wait long enough between each of their flagship releases because we often get spoiled with something new every year.  A while back it used to be one of their traditional entry-level SR-series or mid-fi SE-series updates, but now we get a more exciting variety with a modular (SE180), a discrete R2R (SE300), a powerhouse (KANN), or a Tube (SP2000T).

Expecting a new DAP from A&K this year was inevitable, but nobody knew when and what.  So, when they announced the SP3000T (3kT) right before the CanJam NYC ’24, I wasn’t as surprised at first because I expected something similar to their SP2000T (2kT) based on the design of their current SP3000 (3k) flagship.  But the surprise came later when they revealed that instead of the NuTube module the new DAP will feature a pair of Raytheon JAN6418 miniature vacuum tubes.  After having a chance to briefly hear this DAP at the CanJam show, I got another opportunity to spend two weeks with it now, just enough time to complete my detailed test and analysis which I would like to share with you today.

Unboxing and Accessories.

The 3kT unboxing experience is identical to other flagship SP-series DAPs.  Don’t expect big surprises, though it is still impressive to see a premium quality “cigar” wooden storage box emerging from an all-black cardboard outer box.  The outer box cover had a signature “A” letter in silver on the top and a small print with detailed specs in 10 languages on the back.

Everything was packed neatly inside that wooden storage gift box, but I still encourage you to hold it from the bottom when lifting the top since there are no latches or hinges for the cover to keep it securely attached.  Inside you have a foam cutout under the cover where you will find a leather case, 2 screen protectors, a quick start card, and a warranty card.  The foam cutout inside the main part of the box holds securely 3kT and USB-C cable.

Inside, you will also find their traditional cardboard card with a pocket and microSD card slot cover (plastic dummy microSD card), though another one was already inside the 3kT.  The included standard USB-C to USB-C high-speed cable for charging, data transfer, and usb DAC functionality is high quality, with durable shielding, and adequate gauge wires.  With fast charge mode support, it’s important to use a quality cable for high-speed charging at higher voltage.

Just like with other flagship SPs, A&K included a premium quality leather case for the 3kT model, a deluxe case crafted from shrunken calf leather sourced from Perlinger in Germany and Alcantara in Italy.  According to A&K, the shrunken method used to craft the leather results in natural wrinkles, creating an irregular, yet distinctive texture that enhances its appearance and ensures the color (yellow mustard here) remains vibrant even after prolonged use.

The case fits like a glove, with an opening for a USB-C connector at the bottom, a covered AMP selection and Play/Pause/Skip buttons on the left, generous phone ports and a power button opening at the top, and a generous cutout for the volume wheel on the top right side.  The DAP slides from the left where the side flap tucks in securely inside, providing better protection from the top and all corners.  The back of the case has a large trapezoid shape cutout for the Tube window.  Below it, to add more elegance, there is an Alcantara leather insert.  The case gives this large-size dap a more secure grip when handling it and protects from the SS edges of the chassis digging into your hand.

Since the microSD card slot is covered at the bottom, you have to remove the case to physically access and replace it.  Also, I found the “natural wrinkles” in the texture of the case making it harder to feel the covered side button on the left.  But I’m sure Dignis will have their 3kT case available at some point soon since they always do.

Design.

With dimensions of 141.5mm x 84.7mm x 18mm and a weight of 483g, 3kT is very close to 3k, within a 1-2mm difference and even 10g lighter.  One of the contributing weight factors here is the Stainless Steel 316L chassis used in 3kT, another “the first time” with a unique Silver-color Stainless Steel material featuring Pure Silver plating.

The focus of the design is still around a gorgeous 5.5″ HD touchscreen occupying the front view.  This view of the DAP is also similar to 3k and asymmetric due to unevenly sculptured bevel sides, including a slightly bulging-out area around playback/control buttons on the left and a crown-patterned volume wheel on the right.  But unlike 3k and similar to 2kT, the volume wheel here does not double as a power button.  A dedicated power button is on the right at the top with a typical long press to turn the power on/off followed by a confirmation to shut down or a short press to turn the screen on/off, though I usually prefer a Double-tap to wake up the screen.

Out of the box, the volume wheel was not as easy to turn using just a thumb, I had to use both fingers, and it still has some resistance with a click action felt with every rotation turn of 150 volume steps.  I recall at the CanJam NYC show, the volume knob was easier to turn, so perhaps due to this review unit being fresh, it will loosen up with more use.  Also, identical to 3k, implemented here is a multi-function LED behind the wheel to indicate charging status or bit depth depending on the source file (16bit – red, 24bit – green, 32bit – orange, DSD – purple).  LED light could be disabled in Settings.  The design of the volume wheel has a very detailed and unique crown pattern, typical of a wristwatch.

On the left side, you have the AMP button (a new addition for faster access to the AMP menu to select between OP/Hybrid/Tube) and Play/Pause and Skip control buttons below it, four identical small rectangular buttons located in the upper part of the left side.  They do have a nice tactile response and even spacing, but the addition of the 4^th button created a bit of a problem for me.  I usually brush my finger across the buttons to find the middle play/pause, while here you have 4 buttons, and you have to remember if you are going from the top or the bottom.  Also, as already mentioned, the new “wrinkled” texture of the leather case makes it hard to feel the indents of the buttons.  So, I was mostly using the top left-side hardware button to access the AMP menu.

The top of the DAP has access to a 3.5mm phone output port which is also used for Line Out and Optical out.  Next to it, you have 4.4mm and 2.5mm balanced phone ports that could also be configured as Line Out.  The power button is next to it.  At the bottom to the right, you will find a spring-loaded microSD card slot.  In the middle, there is 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.  The back of the DAP also has a typical A&K asymmetric design with an extra cutout around the volume wheel.  The top of the back has a window to display Tubes “glow” with a background LED lightning.

Under the hood.

As already mentioned in the Intro, A&K has a history of flagship model releases aligned with the introduction of the latest AKM flagship DACs.  When 2 years ago AKM announced AK4499EX, it only made sense that A&K would be the first to introduce it in their 3k design and feature it in 3kT as well.  And it is not just about AK4499EX, but also AK4191EQ in conjunction with AK4499EX.  After the devastating factory fire of 2020, AKM came back strong with a new solution where they separated the digital and analog circuitry of the DAC, partitioning it into AK4191EQ to process the digital signal of D/A conversion (digital filter with sigma-delta modulation and oversampling) and AK4499EX for analog conversion and processing.

It is becoming more common to see ckt boards with a partitioned layout of analog and digital circuits.  Here, the DAC chip itself is partitioned into two separate chips to improve the purity of the analog signal, lower the noise and increase the SNR, and lower the clock jitter by separating digital and analog portions of the clock.  As part of the 3kT design architecture, A&K implemented 2 separate pairs of AK4499EX DAC and AK4191EQ modulator, one pair per L/R channel, for a total of 2x 4499EX and 2x 4191EQ.  This is a different architecture compared to the 3k HEXA design with 6 modules using 4x 4499EX and 2x 4191EQ where they partitioned separate BAL/UNBAL paths.

I’m no longer surprised to see every headphone port available in SP-series DAPs, 4.4mm and 2.5mm balanced, and 3.5mm single-ended (or unbalanced, as A&K calls it) outputs.  The single-ended 3.5mm PO has an output impedance of 1.5ohm and 3.3Vrms output, while balanced 2.5mm has 1.5ohm as well and 4.4mm has 1.4ohm with both having 6.3Vrms output, assuming the unloaded output measurement condition.  Based on my comparative testing between 3k and 3kT, the volume level was nearly the same which confirms that power output hasn’t changed between these models.  Furthermore, each port can be switched to Line Out, and 3.5mm also has Optical SPDIF output.

The touch display is 5.5” HD with 1920×1080 resolution.  The interface is as fast as in 3k, noticeably faster than in previous A&K DAP models thanks to the implementation of the Snapdragon 665 (6125 Octa-core) SoC processor.  The interface is still closed Android so it is hard to compare to other open Android DAPs since I can’t run 3D benchmark apps, but the user interface is noticeably faster than previous 2k and 2kT models.  And there is plenty of processing power to do flawless audio decoding while supporting all the popular lossy and lossless formats, such as WAV, FLAC, WMA, MP3, OGG, APE, AAC, ALAC, AIFF, DFF, and DSF, with PCM rates up to 32bit/768kHz and DSD rates up to 22.58MHz (DSD512).  Also, if you still care, you get MQA playback support, covering Tidal Masters, Local files, External USB, and MQA-CD (ripped).

Just like in 3k, the internal storage of 3kT is 256GB, and you also get microSD external memory expansion up to the latest largest capacity card (A&K tested with 1TB).  I guess it doesn’t matter as much today since many people are streaming and high-capacity microSD cards are relatively cheap, including plenty of 1.5TB available now.  Furthermore, USB-C OTG supports external hard drive storage or usb stick expansion.  According to A&K, their high capacity of 5,050mAh (3.8V LiPo) battery should give you up to 10 hours of playback time under normal IEM listening in OP mode.  Also, fast charging (QC3.0) is supported and should give you a full charge in about 3.5 hours.  This is the same battery and the same solid-state playback time as in 3k.  The playback time will decrease as you drive more demanding headphones at a higher volume and in Tube mode.  As an example, in my testing from 4.4mm output at 60/150 volume, in Tube High Current mode and w/DAR enabled, I got about 6.5-7 hours of playback time.

To support fast charging and speed up data transfer, 3kT uses a USB 3.0 Type-C interface for charging, data transfer, and USB DAC functionality.  WiFi is dual-band, supporting both 2.4GHz and 5GHz.  Along with that, you have OTA firmware update support and of course streaming of many popular apps.  Furthermore, Bluetooth is up to 5.0 with wireless support of not only aptX HD but also LDAC protocols for 24-bit playback over Bluetooth, plus in both Bluetooth Rx and Tx directions.

Unlike 2kT which uses a Korg NuTube module that is similar to a conventional vacuum tube since it operates as a triode tube, the 3kT design switched to use the actual vintage vacuum tubes.  Here they implemented a pair of Raytheon JAN6418 mil-spec vintage miniature vacuum tubes, well-known and highly regarded in the audio industry for portable use.

When dealing with tubes, you have to be aware of the noise/ringing in the event of minor shocks or vibrations.  To address this issue, A&K came up with a modular design using a flexible PCB board attached to the main PCB.  They also implemented a silicone module case along with silicone dampers around tubes, and a silicone tube around vacuum tube leads, all to absorb the shock and reduce shock transmission.  However, some minor resonating ringing could still be audible if you bump the player or tap on it, but you can only hear it when idling or at low volume and only for a very short time since it stops quickly.

Page 2 – GUI overview, Open APP Service.
Page 3 – Sound Analysis, Comparison.
Page 4 – Pair up, Wired/wireless connections, and Conclusion.