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Astell&Kern SEM2 Dual DAC for SE180 Music Player Review

Amps, and DACs, and Bears, Oh My! A comparison of the SEM2 vs. the standard SE180 DAC Module


Replaceable modules aren't anything new in the world of portable music players, but Astell&Kern has finally put their own flair on the design. The SE180 DAP implements this new design for AK, giving the user complete control to change the sound of their music according to their own listening preferences. Why? Because everyone hears differently.

People like choice, and the SE180 music player departs from the design of the SE200, and instead of including multiple digital-to-analog converters in a single device, they have designed the music player to have removable DAC modules. It's not the first time we've seen this kind of design, but Astell&Kern makes it their own and does it well. Now they've released the SEM2, the latest module for the music player. How does it compare? And will there be more on the way?


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Pros:

  • Replaceable modules are compact
  • Snug and secure connection
  • Great sound
  • Customization

Cons:

  • Pricey
  • Can be difficult to unlock and swap out

Overview

Astell&Kern SEM2 is loaded with the Asahi Kasei AK4497EQ Dual DAC. The AK4497EQ can play files up to 32-bit/768kHz PCM and native DSD512. Another module is planned for later in the year, with a further one coming in the first half of 2022. The first two DAC cards support 2.5mm, 3.5mm, and 4.4mm headphone connections and MQA support for locally stored files and playback via TIDAL. There could be different headphone port options coming with the next wave of DAC modules.


Materials & Quality

Like the Astell&Kern SE180 music player, the SEM2 is made with matching aluminum, disappearing into the design when installed. The fit is so precise that it's hard to tell if the module is removable at all. The craftsmanship, in general, is superb, with each button finely cavity milled out for seamless precision. The double-locking mechanism is effective in making sure you have a tight and secure fit of the module inside the music player. The module itself connect to the DAP circuitry by means of a USB-C connection, allowing for fast transfer speeds between the DAC and headphone amplifier sections.

With the detachable module section, the DAP is no heavier than a similar weighted player like the SP2000. It's not unwieldy by any means, but there is some weight involved when considering the overall portability of the device. We certainly recommend using a leather case on the device to protect your investment, because it's not so much the fear of dropping the device as it is scratching the glossy front and back glass finish.

Size-wise it is also comparable to the SP2000, sharing the larger chassis when set side-by-side to the SA700 or SR25. Still palm-able, the SE180 is the player to beat when it comes to the overall customizable sound that you can tailor to your own listening preferences. The only downside is that the module fits so precisely inside the music player that it can sometimes be difficult to eject. You'll need to find the right angle where you can apply enough pressure on each side of the unit which gives you enough clearance from the locking mechanisms while simultaneously using your fingers or fingernails to pull the module out from the small groove located on the back. After a couple of times of struggling, I found what worked best for me and haven't had any issues since.

As expected, all the SEM cards have the exact same dimensions and build quality. You won't find anything different here other than the superb build quality that Astell&Kern is known for.


Sound Quality

(Comparison with the SEM1)

The design choice of the SEM2 is to give the user control to change their music players' sound based off their personal listening preferences. The SE180 DAP does this beautifully with the choice of the SEM1 (which the SE180 comes equipped with) and the new SEM2. The SEM2 utilizes an Asahi Kasei AK4497EQ Dual DAC setup, although it's hard to tell by looks alone, as the modules look identical. Each one has the same configuration as well with 2.5mm, 3.5mm, and 4.4mm analog outputs. The only real way to tell them apart is by the tiny glossed text on the bottom of the module.

As stated in the SE180 music player review, the SE180 DAP comes packaged with the SEM1 module, which is equipped with the flagship ESS ES9038PRO DAC chip. These days DAC chips are just a part of the sound signature equation, and one thing that the SE180 boasts that other DAPs can't is a completely separated DAC section from the rest of the machine. This means that the power and RF signals/noise from the main unit is completely blocked by the engineering design of the DAP. Less noise also means a more pure auditory experience.

The ES9038PRO is an excellent DAC, providing a surprising amount of detail and clarity to your digital audio. I would say it's on the analytical side of the spectrum, but not totally inaccessible for those who prefer a warmer sound. Don't worry though, if you don't like it you can always swap it out for a different DAC from a different module. That single factor is why I've been a fan of iBasso since they allow the user to tailor their sound to their personal preferences: listen to your music the way you want to.

The SEM2 offers a slightly more bodied sound than the SEM1. AK DACs tend to be by nature warmer than their ES counterparts, and the AK4497EQ is not different. Still offering plenty of detail the low frequencies are rounder, offering more perceived bass than the SEM1. Mids are warmer, more energetic, and to me a little more boosted than the SEM1, making guitars sound more in your face. Highs are still detailed, but more rolled off and smoother. The SEM2 is great for genres like classical and jazz, who want a more musical presentation but still want to retain that sense of detail and intimacy in the performances.

Performance-wise the SEM2 is going to be identical to the SEM1, not making any difference in battery life and overall speed of the SE180 music player from power draw.

Module Sound Signatures Recap:

  • SEM1: Analytical, Detailed, Resolute
  • SEM2: Musical, Warmer, Detailed

Features

Interchangeable Modules - With the SE180 DAP, Astell&Kern wanted to expand on the multi-DAC idea that was first introduced with the SE200. Like the SE200, different DACs can be used in one DAP, but for the SE180 they decided on implementing a new system of interchangeable modules. Swap-able cards or modules aren't new, as companies like iBasso have been doing them for years with their DX line of music players, but Astell&Kern is quick to point out that their system is different from the competition. Unlike iBasso, the SE180 is a module-separated product that increases the convenience of connection between the main body of the player and the module. It features an innovative double-locking design that securely connects each component while providing smooth lines that naturally flow without any sense of separateness between the two pieces. By applying different DAC/Amplifier configurations and adjusting the tuning and outputs for each module, the user can choose the most suitable module for their sonic preferences for high-end audio qualit.

Modules Double Lock for Ease of Use - The biggest difference between the SE180 and other products that use interchangeable modules is that the SE180 uses a double-locking mechanism rather than screws to fasten the module to the body. The first locking structure attaches the module and the body. The second locking structure informs the user that the module has been securely fastened to the main body. The spring-supported internal connectors of the main body allow reliable audio signal connection and are used to prevent connection failure in case of external shock to the player when on the go.

Astell&Kern Audio Technology Forms the TERATON ALPHA Sound Solution - TERATON ALPHA is AK's ultimate Sound Solution to produce audio playback that is close to the original sound through the audio output interface by use of effective power noise removal, efficient power management, and amplification with minimal distortion. TERATON ALPHA features Astell&Kern's patented technologies, which are the result of tens of thousands of hours of continuous research and development to produce the sound close to the original sound the artist and producer intended.

Next-Generation Advanced AMP Technology - It is extremely difficult to push beyond your previous best. With the SE180, Astell&Kern applied Next Generation AMP technology to push beyond the sound quality others feel is acceptable for Premium Hi-Fi Sound to produce the best sound possible. From the selection of OP-AMP parts to circuit design, board layout, and tuning, everything has been completely redesigned to produce the best sound. It is difficult to improve the Signal-to-Noise Ratio (SNR) while maintaining a high output.

Circuit Separation Structure of Main Body and Module - By physically separating the main body from the All-in-One DAC module, Astell&Kern completely blocks power and RF noise that may occur from the main body. This creates an independent structure that prevents noise from interfering with music playback.


Verdict

The SEM2 is a great alternative to the more analytical signature of the SEM1 that comes with the SE180 music player from Astell&Kern. Both modules sound phenomenal and are small enough to potentially take both with you while traveling. Customization means you can personalize your music player to what you want without the need for adapters or external gear. The SEM2 module comes equipped with a very capable AK4497EQ in a dual-DAC configuration, giving you more body and warmth to your music. The low end is perceptively beefier, though never bloated. Mids and highs provide energy and detail, and like the AKM DAC in the SE200 music player, is a welcome option for those not keen on the more analytical sound signature of most Astell&Kern DAPs. We like to have high-quality options, and Astell&Kern is finally providing them.


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What's in the Box

  • SEM2 DAC/AMP Module for SE180 DAP Music Player
  • Manual/Paperwork

Specifications

Technical Features
  • Model: PAP12
  • Body Material: Aluminum, Stainless Steel, Polycarbonate
  • Body Color: Moon Silver
  • 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), Stereo / DSD512(1bit 22.4MHz), Stereo
  • Output: Unbalanced Out (3.5mm), Balanced Out (2.5mm, only 4-pole supported / 4.4mm, only 5-pole supported)
  • Output Level: [Normal Gain] Unbalanced 2Vrms / Balanced 4Vrms (Condition No Load) [High Gain] Unbalanced 3Vrms / Balanced 6Vrms (Condition No Load)
  • DAC: AKM AK4497EQ x2 (Dual DAC)
  • Decoding: Support up to 32bit / 768kHz Bit-to-Bit playback
  • Dimensions: 3.03"(77mm)[W] x 2.99"(76mm)[H] x 0.78"(19.9mm)[D]
  • Weight: 3.53oz (100g)
  • Operating Temperature: 3.53oz (100g)
  • Playback Time: about 10.5hours (FLAC, 16bit, 44.1kHz, Vol.50, LCD Off)
AUDIO Performance
  • Frequency Response: ±0.07dB (Condition : 20Hz~20kHz) Unbalanced / ±0.06dB (Condition : 20Hz~20kHz) Balanced ±0.68dB (Condition : 20Hz~70kHz) Unbalanced / ±0.67dB (Condition : 20Hz~70kHz) Balanced
  • Signal to Noise Ratio: [Normal Gain] 122dB @ 1kHz, Unbalanced / 124dB @ 1kHz, Balanced [High Gain] 125dB @ 1kHz, Unbalanced / 127dB @ 1kHz, Balanced
  • Crosstalk: [Normal Gain] -138dB @ 1kHz, Unbalanced / -145dB @ 1kHz, Balanced [High Gain] -138dB @ 1kHz, Unbalanced / -147dB @ 1kHz, Balanced
  • THD+N: [Normal Gain] 0.0006% @ 1kHz, Unbalanced / 0.0005% @ 1kHz, Balanced [High Gain] 0.0008% @ 1kHz, Unbalanced / 0.0006% @ 1kHz, Balanced
  • IMD SMPTE: 0.0002%, 800Hz 10kHz (4:1), Unbalanced / 0.0002%, 800Hz 10kHz (4:1), Balanced
  • Output Level: 3.5mm (1ohm) / 2.5mm (1.5ohm) / 4.4mm (1.5ohm)

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