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Astell & Kern CA1000T ($2299): Nutube sounds adds to a legend

Astell & Kern CA1000T ($2299): Nutube sounds adds to a legend


A&K build quality
Superb sound
Added depth of tube sound-even with slight grain I like it.
Tube sound adds enough to the bass, like a tube sound should
Mids are still very detailed
Gorgeous good looks
Streaming ability means this might be all you ever need for all your purposes
Ease of access to the “amp” section on the lower part of the top (below screen)


Not mine
OS noticeably slower than CA1000-loss of 0.5 stars
Not everyone likes tube sound-can be slightly grainy
Not mine

Astell & Kern CA1000T ($2299): Nutube sounds adds to a legend




While sitting at T.H.E. Show, in June a gentleman came up to the booth where will and I were sitting. I had just returned from my room with the outstanding CA1000, in preparation for returning it to our contact, Jason. As I was packing it up, I said, “I’m just packing this up, but if you want to hear this outstanding piece, I can remove it.” He replied,” actually I’m here to pick it up.” It was indeed Jason. In gushing over the CA1000, I mentioned how if I were to only have one device, which could be considered a DAP, a headphone amp and a streamer, it would be the CA1000. He then mentioned, “I can send you the CA1000T, if you like.” I said, “yes please.”

This review follows on the heels of the outstanding CA1000, which as stated above (is the truth) is an outstanding device. I thank Jason & Astell & Kern for the item, and upon finishing my time, the unit will be sent back (unfortunately).


CA1000 review



  • Model: ACRO CA1000T
  • Body Color: Rich Gray (Black)
  • Body Material: Aluminum
  • Display: 4.1 inch 720 x 1280 touch screen
  • Supported Audio Formats: WAV, FLAC, WMA, MP3, OGG, APE, AAC, ALAC, AIFF, DFF, DSF, MQA
  • Sample rate: PCM : 8kHz ~ 768kHz (8/16/24/32bits per Sample)
    DSD Native: DSD64(1bit 2.8MHz), Stereo / DSD128(1bit 5.6MHz), Stereo / DSD256(1bit 11.2MHz), DSD512(1bit, 22.4MHz) Stereo
  • Output Level (Headphone Out):

[Low] Unbalanced 2Vrms / Balanced 4Vrms (Condition No Load)
[Mid] Unbalanced 4Vrms / Balanced 8Vrms (Condition No Load),
[High] Unbalanced 6Vrms / Balanced 12Vrms (Condition No Load),
[Super] Unbalanced 8Vrms / Balanced 15Vrms (Condition No Load)

  • Output Level (RCA Out): 2Vrms (Condition No Load)
  • Output Level (XLR Out): 4Vrms (Condition No Load)
  • Recommended headphone impedance: 32 ohm – 600 ohm
  • CPU: Quad-Core
  • DAC: ESS ES9039MPRO x2 (Dual-DAC)
  • Vacuum Tube: KORG Nutube 6P1 x2
  • Decoding: Support up to 32bit / 768kHz Bit to Bit playback
  • Headphone Outputs: Unbalanced (3.5mm, 6.35mm) / Balanced (2.5mm, 4.4mm)
  • Analog Inputs: 4.4mm x1
  • Analog Outputs: XLR (Stereo pair) x1, RCA (Stereo pair) x1
  • Digital Inputs: Coaxial x1, Optical x1, USB(Type-C) x1
  • Digital Outputs: Optical(3.5mm) x1, USB(Type-C) x1
  • Wi-Fi: 802.11 a/b/g/n/ac (2.4/5GHz)
  • Bluetooth: V5.0 (A2DP, AVRCP, Qualcomm® aptX™ HD, LDAC)
  • Dimensions: 4.12″(104.9mm)[W] x 1.77″(45mm)[H] x 6.13″(155.8mm)[D]
  • Weight: about 34.56oz (980g)
  • Feature Enhancements: Firmware upgrade supported (OTA)
  • Operating Temperature: 0℃ ~ + 40℃ (32℉~ 104℉)

Audio Specs:

  • Frequency Response: ±0.031dB (Condition: 20Hz~20kHz) Unbalanced / ±0.029dB (Condition: 20Hz~20kHz) Balanced /

±0.033dB (Condition: 20Hz~20kHz) RCA / ±0.002dB (Condition: 20Hz~20kHz) XLR ±0.079dB (Condition: 20Hz~70kHz) Unbalanced / ±0.029dB (Condition: 20Hz~70kHz) Balanced /
±0.080dB (Condition: 20Hz~70kHz) RCA / ±0.008dB (Condition: 20Hz~70kHz) XLR

  • S/N: 108dB @ 1kHz, Unbalanced / 112dB @ 1kHz, Balanced / 121dB @ 1kHz, RCA / 128dB @ 1kHz, XLR
  • Crosstalk: -115dB @ 1kHz, Unbalanced / -112dB @ 1kHz, Balanced / -138dB @ 1kHz, RCA / -145dB @ 1kHz, XLR
  • THD+N: 0.004% @ 1kHz, Unbalanced / 0.002% @ 1kHz, Balanced / 0.0005% @ 1kHz, RCA / 0.0003% @ 1kHz, XLR
  • IMD SMPTE: 0.0007% 800Hz 10kHz (4:1) Unbalanced / 0.0007% 800Hz 10kHz (4:1) Balanced /0.0007% 800Hz 10kHz (4:1) RCA / /0.0007% 800Hz 10kHz (4:1) XLR
  • Output Impedance: 3.5mm, 6.35mm (1ohm) / 2.5mm, 4.4mm (2ohm) / RCA (4ohm) / XLR (9ohm)

Clock Source:

Clock Jitter: 25ps (Typ)Reference Clock Jitter: 70psStorage:

  • Built-in Memory: 256GB [NAND]
  • External Memory: microSD x1 (Max. 1TB)


  • Capacity: 10,100mAh 3.8V Li-Polymer
  • Charge Time: about 5hours (9V / 3A PD2.0 Fast Charging)
  • Playback Time: about 11hours (Standard: FLAC, 16bit, 44.1kHz, Unbalanced, Vol.40, LCD Off, OP AMP, Low Gain)
  • Supported OS: Windows 10, 11(32/64bit), MAC OS X 10.7 and up

In The Box:

USB-C charging cable
Owner’s manual
Screen protectors

Filter Response:

  • Minimum phase (Default): Low latency, Minimal pre ringing and low passband ripple
Screenshot 2023-08-05 at 9.32.25 AM.png
  • Linear Phase Apodizing: Full Image rejection by FS/2 to avoid any aliasing, with smooth roll-off starting before 20k
  • Linear Phase Fast Roll-Off: Most Common filter with clean suppression and high rejection, best for music with high transients. Provides crisp clean highs
Screenshot 2023-08-05 at 9.36.31 AM.png
  • Linear Phase Slow Roll-Off: Low group delay and symmetrical inputs response. Less ringing than Linear phase fast roll off. Punchier bass than LPFR, with clean highs
Screenshot 2023-08-05 at 9.37.19 AM.png
  • Minimum Phase Fast Roll-Off: Minimal Pre-Ringing, preferred for Imaging and soundstage. No aliasing in frequency domain. Stronger bass than Linear Phase, clean highs
Screenshot 2023-08-05 at 9.38.05 AM.png
  • Minimum Phase Slow Roll-Off: Non Symetrical filter designed to minimize pre ringing. Strong punchy bass with good transient attacks
Screenshot 2023-08-05 at 9.38.30 AM.png
  • Minimum Phase Slow Roll-Off: Low Dispersion Provides a nice balance of the low latency of Minimum phase filters and the Low Dispersion of Linear Phase filters. Minimal pre-ringing is added to achieve the low dispersion in the audio band
Screenshot 2023-08-05 at 9.38.49 AM.png


One of the biggest differences between the CA1000 and the CA1000T are the Twin Triode KORG Nutube tubes (x2). Similar to the ones used in the Cayin C9, the A&K incorporates a system where you can run anywhere from full tube goodness, to full solid state. Keeping the channels separate also means the balanced sound can travel its own path instead of combining, then separating via a balanced transformer, thus keeping the circuits separate and without additional “conditioning.” An additional switch on the top-front (far right), brings up the sub-menu used to change the state of amplification, giving the user quick access. Much like DAP’s can be switched between dual DAC’s or Class A/AB using a switch, the A&K incorporates the touchscreen for help in deciding what level of tube or solid state (hybrid) you would like to use. This is only available for the headphone jacks on the front. The CA1000T offers a complete balanced circuit that separates left and right channels with two vacuum tubes via the dual DAC’s, creating a more natural and softer sound in the tube state. Those DAC’s by the way are the newest ESS, the dual ES9039MPRO promoting a more voluminous and vivid sound. MQA stereo hardware is incorporated into the chip as well. The roadmap below guides you through the usage of chips, OPAMP’s and Nutubes all the way to whichever end process you choose. The OPAMP’s used are A&K’s own design for enhanced, deeper bass response as well as clear highs. Combine all of the above at you get a max of 15Vrms regardless of output option.

Screenshot 2023-08-05 at 9.39.43 AM.png

The OP AMP mode (bottom left on sub-menu circle) puts Astell&Kern’s AMP technology to use, delivering extreme clarity and dynamic sound, while TUBE AMP mode (bottom right on sub-menu circle) provides a uniquely warm and musical sound. HYBRID AMP mode (five options between OP AMP & Tube Amp, getting progressively more “tubish” as you go clockwise around the sub-menu circle), which is a first for digital audio players, enhances the resolution and clarity of the existing TUBE AMP mode to express more musical detail (the closer you are to solid state). Each of the five hybrid options does enhance musical detail, but the closer you get to the full tube sound, the less this is evident as one would expect.


As we know, while tubes sound fabulous to most of us, they are prone to external pressures from bumping and shocks. This gives off unwanted vibrational aspects to the sound we hear, essentially ruining the tube experience if not isolated. A&K has thought of that as well. To minimize and isolate this potential structural problem, both sides of the vacuum tube are fixed with flexible silicon covers minimizing shocks; while a magnetic force is used to physically separate it from the PCB. This offers greater stability and isolation when the tube is operational.

Screenshot 2023-08-05 at 9.40.52 AM.png

A&K’s Teraton Alpha provides patents, which essentially minimize distractions in any part of the working power unit to provide noise reduction when the device is in use, regardless of the source or option used (OP AMP or Nutube). This is also better audio wiring, which improves the crosstalk (mainly on the amp parts); a complete mute of unused channels (such as when in Nutube or solid-state mode), keeping noise levels at the lowest level while listening; and a silver plating shield can, which prevents various noise and electromagnetic interference from affecting the audio block.

Another nice feature is the “Crossfeed” widget, accessed from the dropdown menu in OS. In a headphone environment in which the left and right channels are clearly separated, ear fatigue may increase during prolonged listening. When you turn on Crossfeed, the experience of crisp, but comfortable sound begins (less long-term fatigue). Crossfeed mixes parts of the original signal from one channel and sends that signal to the opposite channel with a time difference to center the sound image, much like balanced or a holographic sound. Crossfeed can be changed in “Settings” (slider-based), with options such as Shelf Cutoff, Shelf Gain, and Mixer Level, allowing you to change the settings according to your listening preferences. You can even make your own custom settings as well.


A&K’s UI is a custom Google OS, with a familiar layout to the CA1000, but this time around, it is almost painfully slow. Especially when you use a third-party app such as Tidal or Qobuz (must be downloaded to a computer, then the .atk file dropped onto the A&K, then installed), located under “Services,” in the main Settings layout. The screen layout is quite good though, with easily manipulated sub-menus and options. Just slow. I also found that when I used Tidal, the volume knob sometimes failed to register quickly, causing me to scroll repeatedly to raise the volume. This was while charging, and I will investigate this further.

“ReplayGain,” which is also accessed via the dropdown menu from the top of the OS, automatically adjusts the volume of each song; matching volume levels between songs to the level you have set. This works across sources as well, ridding us of the annoying volume jump between different sources.

Coming with Roon Ready as well as MQA authorization, and AK’s File Drop (wireless transfer); the CA1000T supports native DSD512 up to 32bit, 768kHz; should you have that format. LDAC and aptxHD also gives you the latest formats from those source codes as well.

*A note about potential issues: while the unit was well packed, it came without the protective box, and assorted items. Only the CA1000T was sent, and it is fairly obvious from the looks that this unit has been handled by reviewers repeatedly. My hope is that they treated this well, but it does show signs of prior “heavy use,” to put it politely; along with the normal shipping company’s “safe handling.” To me, this is not any indication that A&K bears responsibility, and if this were my unit, it would be treated with the utmost care. As a result, the volume wheel stuck in high humidity situations coupled with the previous mentioned handling.


Physical Layout & Form:

On the front side (L to R): 1-3.5mm TRS output; 1-2.5mm TRRS, balanced output; 1-4.4mm Pentaconn, balanced output; and a 6.35mm TRS output.

The back:

  • 2x mini-XLR outputs, balanced output, used with a set of monitor speakers
  • 1x stereo RCA output, single-ended output, to connect another amplifier, or a set of speakers or into a system to be used such as my Yamaha CRX-E150 (it is all I have out currently due to the move)
  • 1x coaxial in, to use the CA1000 T as a DAC
  • 1x optical in, used as a DAC as well
  • 1x 4.4mm Pentaconn In, for a balanced DAC when using the A&K as a headphone amp
  • 2x USB-C, one for charging, one for DATA – USB3.1 compliant
  • 1x micro-SD port to expand the internal storage to 1Tb, plus 256Gb of internal memory

The top:

  • a 4.1” 720×1280 touch screen, the same found on some of the brand’s DAP
  • 5x control buttons, power on/off, previous, play/pause, next, AMP (to switch between the three modes mentioned above)
  • an illuminated Astell&Kern logo indicating the playback/amp mode (at the top, above the screen when lowered)- [Playback mode]: 16bit-red, 24bit-green, 32bit-blue, DSD-purple; [Amp mode]: OP AMP: red, Tube Amp: orange, Hybrid Amp: blue green

The CA1000T shares the same shell as the CA1000, with only the front & back panels (top actually) changed according to the included items. Also changed is a gold-accented inner volume ring in stainless steel, which they say gives a more luxurious look. Gold and black together do look good. If you are familiar with the CA1000, then you should have little issue with the layout and functioning. The only other change is the aforementioned “Astell&Kern” logo on the top center, which shows the amp color use and decoding color. A nice change, which I likened to the colors used to accent the Tone2 Pro from Khadas, under the control wheel (another fabulous unit).

The black (Rich Gray) color gives the unit a stealthy look and the highlighted logo on top lends a sense of purpose, especially when formats change. Compared side by side, the CA1000T looks more sinister, subdued and ready to hold a spot hidden on your desk; only to jump out when in use. While I like the black (better), the silver of the CA1000 shows off the angular surface more to me. Where the CA1000T is subdued, the CA1000 is curvaceously angular. Pick your poison.

Functionally speaking, you will have little issue, even if you are not familiar with the CA1000. Remember though, that third party apps such as Qobuz or Spotify must be downloaded onto an SD card, then installed from the card. I did that for Qobuz on the CA1000, but not the CA1000T, sticking with Tidal and SD cards, Tidal mainly.

I also used the RCA outs to my Yamaha small system, much like I did the CA1000 with the A-301, with no issues. I could have hooked the CA1000T into the excellent little Schiit Modi 2 Uber via optical S/PDIF, but saw no need; since the A&K DAC section was superior. Needless to say, that the performance digitally would have been of a cleaner nature when hooking up as a streamer. If I was to keep this (unfortunately not…), I would hook the CA1000T into my two-channel for streaming via optical and BT a set of powered speakers as well. An unfortunate aspect of my gear being packed away.




Whether utilized as a streamer, headphone amplifier or pre-amp; the CA1000T excels in the same way the CA1000 did. Except here you have the new ESS chips running the show as well as the Korg Nutubes with which to vary your source sound. My preference was straight Nutube listening, but the benefit of solid state cannot be understated: it is superb, and right up there with the best sources I have ever reviewed. Another reviewer stated that if he were to have one source to use as a headphone amp, streamer and pre-amp; the CA1000T would be it. This is exactly what I said about the CA1000, and repeat here.


*The SS/Hybrid/Nutube options are not available on the RCA connections I used. I am unsure of the others on the backside, due to a lack of testing.

There is no getting around the flexibility of the CA1000T with regard to changing the source sound you hear. Solid state allows the music to shine through unencumbered by anything. Isolation is excellent, and a black background is not only an expectation or demand; but reality. Crystalline in nature, with a decidedly excellent weight to the notes allows the music to shine based upon the engineer’s requirements. No hindering of sound is had. I do find that even though the sound is clear sonically, there is a slight volume drop going between solid state and full Nutube. Mids, while not suffering seem a bit behind the overall scheme in SS mode as well. Nutube pushes the mids forward for good or ill, and you can tailor that by going into the Hybrid mode.

Pretty much any skewing of sound can be had by going SS or Nutube, along with the five Hybrid choices with progressively more tube input going clockwise in choice. My second favorite choice was what I will call “setting one,” which is the first of the Hybrid settings, skewing more towards SS. The Nutube certainly still had a small effect, adding mids from the wonderful tubes to make a tube-like sound, which also presented excellent clarity and detail. Bass was taut and reached deeper due to the input, with a slight smoothing of character along with the mid-exuberance.


The best of both worlds was mid-Hybrid, with the SS still allowed to show off its clarity, while the Nutube added depth to the bass, and thickness to the mids, which for me were pushed a bit too far forward. This seemed odd, until I realized it was the excellent clarity, which seemed to bother me. I prefer a richer, warmer signature, which was provided in full-Nutube mode.

Each time you initiate Nutube mode from the settings, a red circle works its way around the sub-menu while the tubes pre-heat. Once done, you can indeed hear when the tubes kick in. A nice feature here is still in place as well. Double tap the screen from off, with the Amp sub-menu up and you return to that sub-menu. Yes, this is like a Smartphone, but having the ability to quickly change the SS/Nutube settings this way is a nice touch. Of course, hitting the on/off button will do that as well.



The A&K ACRO CA1000T is expensive. Even taken into consideration against other streaming devices of such character. But those other expensive streamers are really only a one trick pony. “Stream or die!,” they say. Meanwhile, the CA1000T turns into a DAP, much to the astonishment of the other top tier DAP’s. “What is this sorcery?!,” they say. Without a bother, the CA1000T, then hooks into the KANN MAX or my aged AK120 Titan, becoming a headphone amplifier. “Blasphemey!,” the well-known headphone amplifiers shout from their perch. The CA1000T then hooks into your two-channel as a pre-amp for whatever source you want injected into the soul of it. “WHaaaa?!?!,” the others shout, as they cower away knowing they cannot compete.

The CA1000T then uses its final trick to the nodding approval of your fine 50-year-old tube amplifier as it switches on the Nutube. For you see, that ancient wisdom coming forth from your Dynaco or McIntosh or other such sort knows. They see the ability to all of the above, with extraordinary abilities as a positive, not a single-tricked item, with added gizmos to show off. They know that the CA1000T is of the sort, that it can hold its place in any of those situations, without diminishing the results. Without jading those results, because the performance is less than others in whatever category is complaining. The A&K ACRO CA1000T gets it.

Many are tired of having a multitude of devices with which to care and use so that we get our “value” out of them. The A&K understands that it is expensive, but challenges you to add up all you have spent on individual items in the categories listed above, and understand that while those items are good to excellent; it can do all of that in one device. I personally would bet (and know) that the cost of all of those far surpasses the cost of the CA1000T, and one could arguably state that the A&K is a bargain. I dare you to use this argument with your significant other (or your own mind), saying you are saving money and getting rid of pieces as a result. To me, this is the true beauty of the CA1000T: they took the excellence of the CA1000 and improved upon it, making it a very noteworthy addition to the market, and one you should most definitely consider in any of the situations I listed above. It excels in them all.

I finish this while listening to Nat King Cole’s “L.O.V.E” on my Meze 99Classics with the excellent DDHiFi BC150B 4.4bal and the small Yamaha system of which I inserted the CA1000T. It is superb, and I would gladly pare my units down to make room for this in any situation. Especially if they could sort out a faster OS. To me, that is the only “major” flaw, and needs addressing to make the CA1000T near-perfect. Your opinion of course may differ, but it is well worth a hard, serious look to make that differentiation.

Thank you, Jason and A&K for the chance to hear the “upgrade” to the model I loved in the CA1000. The CA1000T is worth it.