AKM's AK449x DAC chip, since the release of AK4495 in 2016 has been about six years, we have seen AK4495, AK4493, AK4490, AK4497 and other DAC chips appear on portable players, sound cards, decoders and other devices. The flagship model AK4499 DAC was released in December 2018, and the original high-end model was scheduled to be available in late 2019-early 2020, but due to the epidemic, chip shortage, plant fire and the positioning of its own AK4499 chip, it was difficult to produce. Fortunately, since the second half of 2020, the player, sound card and decoder of the AK4499 DAC have appeared one after another. The main significance of AK4499, from the perspective of the official sound of AKM, in addition to the super performance of the digital part, is also the first time in more than a decade to release a current output DAC chip, placing I/V outside the DAC chip [voltage type refers to built-in I/V]. Judging from third-party data, AKM officials have even given the view that I/V externals can make audio performance have more room to play. So, let's take a look at how the decoder of the AKM AK4499 DAC chip that netizens specially purchased for testing- SMSL M400 performed.
Shuangmu Sanlin S.M.S.L M400 USB external decoder
Appearance, key features and specifications
The Shuangmu Sanlin SMSL M400 decoder is similar to the device positioning currently using the AK4499 DAC chip, and the price will not be too low, which is limited by the chip positioning and price. M400 price of more than 5,000 yuan, in general, all aspects of the configuration is not too high-end, the appearance is only the average level of SMSL, as a desktop decoder, can only say that the real machine looks better than the photo so a little. But in terms of details, don't ask for too much.
<b>1. Appearance:</b> SMSL M400 decoder appearance workmanship and design is very general, the top cover is a black acrylic panel, the new state is indeed a good visual effect, but it is difficult to maintain, such as electrostatic ash absorption, fingerprint collection, wear-resistant, but also consider and SP400 ear with "suit" stacking effect will not be good. The surface of the black aluminum material in a circle of the fuselage is general, the assembly accuracy is general, if it is placed in front of a small desk with ear amplifiers, it feels that the degree of refinement is not good. It looks small and delicate on the sound cabinet.
The front side of the decoder is a color LCD screen on the left, which usually displays the volume number and the parameters of the input signal, such as the sampling rate of the PCM. In addition, the machine has some functional settings that need it to display. We'll talk about it later in the feature description. The assembly of this screen has a serious defect, that is, its LCD panel is directly stuck in the front of the chassis opening, and the panel is completely flush, without front glass protection. So one careless... The liquid crystal is broken. Why is it pressed bad? For example, if we plug in the back of the wire, it is easy to need to top it in front? If you are not careful, it will break.
On the right side of the front panel is the knob, which has a poor feel and is loose and crumbling. The middle area is the keypad, which is useful in the function settings. There is a very small opening in the center, and the red Led work indicates the status when the machine is in standby.
<b>2. Interface:</b> The back of the SMSL M400 decoder is a conventional input-output interface. In addition to the power interface, a USB-B input interface, an IIS digital signal input for the HDMI interface, and an S/Pdif input interface for coaxial RCA and optical fiber are provided. On the output side, there is a pair of RCA Lineouts and a pair of XLR balanced line outputs. In terms of THE IIS input for HDMI, the pin definition is officially explained, and there are two specifications to choose from in the software. The DSD section, as well as flag, has custom specifications to choose from in the software. Unfortunately, only the Sound MR1 in our hands provides HDMI IIS output, but it is not compatible. In addition, there is a small antenna on the back for Bluetooth signal reception.
<b>3. Main functions:</b> Let's briefly understand the main functions of the M400 decoder through the screen shooting diagram of the M400 decoder. As shown in the figure, the first line of input options does not seem to be automatically recognized, without Auto. In addition to the several wired inputs mentioned above, Bluetooth inputs are also included. The next few options mainly include several sets of IIS input specification switching and settings. In addition, you can set whether the volume output is adjustable or locked at maximum. In addition, the AK4499 DAC comes with pcm digital filter type options and a combination of DSD filter width and narrow solutions. In addition, the XLR balanced output also takes into account the difference in phase between the two different connection methods and can be switched within the software. Overall, the operation is still easy to get started. The only thing to complain about is that if you don't use the remote control, after the setting is completed, there is no return key, you can only automatically jump back to the main interface, in order to adjust the volume, this time seems to be a little long by default, about 20 seconds or so.
Shuangmu Sanlin S.M.S.L M400 USB External Decoder - Screenshot of Features
The design of the remote control looks relatively simple, but the volume, input switching and other functions are still more convenient. Moreover, the official also designed the anti-false touch function of the remote control with the lock by default, which requires pressing the C key to operate. This feature is good is good... I just don't read the instructions and really can't understand. In addition, it is worth mentioning that with the SP400 ear amplifier, the SP400 also has a separate remote control. And it can be coded without stringing.
<b>4. Talking about voltage type and current type DAC chip:</b> The so-called voltage output and current output refer to the signal before the DAC chip is finally output to the analog circuit as a changing voltage or a changing current. Obviously, in audio equipment, sound cards, decoders and other equipment need to convert digital signals into analog signals, through the changing voltage to transmit to the next level of amplification such as the previous stage or power amplifier. The current delta-sigma DAC or R-2R DAC or the D/A circuit in the digital circuit textbook are all converted into the corresponding changing current values of the digital 01 signal, and all need to be I/V converted. The so-called voltage DACs, such as AK4495, AK4493, AK4497, are built-in I/V circuits. The current-type DAC, on the other hand, allows the I/V part to be implemented through off-chip circuitry.
Common voltage DACs include Cirrus Logic CS4398, CS43131 and so on. Common current DACs such as PCM1792, PCM1794, ESS902x Pro series, etc. (ESS partial voltage DACs also seem to provide current output modes, such as the early ES9018K2M?). )。
<b>5.AKM's AK4499 DAC:</b> This DAC chip is the flagship model of AKM and the first time that a current output DAC has been released, including the previous generation AK4397 flagship. According to the official introduction, it has 4 built-in D/A channels, which can support 4 channels of parallel output, and the signal-to-noise ratio of 140dB can be reached in this state. That is to say, if the stereo decoder uses an AK4499 in the left and right channels, the indicator can be achieved. The SMSL M400 is used as a single AK4499, but it can also be produced in parallel for every two D/A channels [AK4497 is two D/A channels each, and the official nominal combined mono output is 131dB signal-to-noise ratio].
In terms of specifications, the AK4499 should be much different from the AK4497, after all, at that time, it was possible to decode the hardware of PCM's 32bit/768kHz and DSD512, and the 16-core XMOS XU216 could also be matched in terms of USB channels. In addition, the M400 decoder can also support MQA decoding, Bluetooth uses CS8675 chip, can support LDAC and Haibei Music's UAT Bluetooth wireless solution.
In other configurations, such as high-precision clock chips, we can refer to official information. However, in the most critical AK4499 DAC as a current output DAC, it needs to be used with an external I/V circuit [generally completed by using an op amp chip], the official did not go into details, but wrote the OPA1612 op amp in the manual, but it was not clearly used in I/V or LPF, or elsewhere.
Let's do an objective test
Objective testing
Objective testing, since the SMSL M400 decoder is typical in terms of output, in the USB section we tested RCA Lineout and BAL Lineout separately. In addition, the test was carried out under the LDAC Bluetooth connection, using the Lineout RCA output. The Haibei UAT test was originally a very interesting part, but the test results are somewhat bizarre and are for reference only. In actual tests, the maximum output voltage is 2.3Vrms under the unbalanced output of RCA, and the balanced XLR output is ±2.3Vrms. Tests are based on the sharp filter option under the first PCM.
Shuangmu Sanlin S.M.S.L M400 USB external decoder - frequency response curve @Lineout
Shuangmu Sanlin S.M.S.L M400 USB external decoder - frequency response curve @BAL
Shuangmu Sanlin S.M.S.L M400 USB External Decoder - Noise Distribution @Lineout
Shuangmu Sanlin S.M.S.L M400 USB external decoder - noise distribution @BAL
Shuangmu Sanlin S.M.S.L M400 USB External Decoder - Dynamic Range @Lineout
Shuangmu Sanlin S.M.S.L M400 USB External Decoder - Dynamic Range @BAL
Shuangmu Sanlin S.M.S.L M400 USB External Decoder - Total Harmonic Distortion @Lineout
Shuangmu Sanlin S.M.S.L M400 USB External Decoder - Total Harmonic Distortion @BAL
Shuangmu Sanlin S.M.S.L M400 USB External Decoder - Intermodulation Distortion @Lineout
Shuangmu Sanlin S.M.S.L M400 USB External Decoder - Intermodulation Distortion @BAL
Shuangmu Sanlin S.M.S.L M400 USB external decoder - resolution curve @Lineout
Shuangmu Sanlin S.M.S.L M400 USB external decoder - resolution curve @BAL
Test the project
THE
BALL
LO96
BAL96
Noise level, dB (A):
-94.9
-95.1
-116.7
-117.4
Dynamic Range, dB (A):
94.9
95.1
116.7
117.4
Total harmonic distortion, %:
0.00053
0.00024
0.00031
Intermodulation distortion, %:
0.00512
0.00490
0.00088
0.00068
Stereo resolution, dB:
-94.8
-110
-115.2
Shuangmu Sanlin S.M.S.L M400 USB External Decoder - Frequency Sweep @Lineout
Shuangmu Sanlin S.M.S.L M400 USB external decoder - resolution test @Lineout
Shuangmu Sanlin S.M.S.L M400 USB external decoder - frequency sweep 96kHz@Lineout
Shuangmu Sanlin S.M.S.L M400 USB external decoder - frequency sweep DSD@Lineout
Shuangmu Sanlin S.M.S.L M400 USB external decoder - resolution frequency analysis @Lineout
From the objective test to the SMSL M400 objective indicators are not a problem, all aspects of the performance is good, of course, the past AK449x of various types of equipment test indicators are good. However, after all, the AK4499 has an external I/V, and the objective indicators of the M400 are satisfactory. If you are very interested in the test results, it is recommended to pay attention to the THD and IMD at 24bit/96kHz, which are quite low.
Shuangmu Sanlin S.M.S.L M400 USB external decoder - frequency response curve @LDAC44.1 Lineout
Shuangmu Sanlin S.M.S.L M400 USB external decoder - Frequency response curve @LDAC48 Lineout
Shuangmu Sanlin S.M.S.L M400 USB external decoder - noise distribution @LDAC44.1 Lineout
Shuangmu Sanlin S.M.S.L M400 USB external decoder - noise distribution @LDAC48 Lineout
Shuangmu Sanlin S.M.S.L M400 USB External Decoder - Dynamic Range @LDAC44.1 Lineout
Shuangmu Sanlin S.M.S.L M400 USB External Decoder - Dynamic Range @LDAC48 Lineout
Shuangmu Sanlin S.M.S.L M400 USB External Decoder - Total Harmonic Distortion @LDAC44.1 Lineout
Shuangmu Sanlin S.M.S.L M400 USB External Decoder - Total Harmonic Distortion @LDAC48 Lineout
Shuangmu Sanlin S.M.S.L M400 USB external decoder - intermodulation distortion @LDAC44.1 Lineout
Shuangmu Sanlin S.M.S.L M400 USB external decoder - intermodulation distortion @LDAC48 Lineout
Shuangmu Sanlin S.M.S.L M400 USB external decoder - resolution curve @LDAC44.1 Lineout
Shuangmu Sanlin S.M.S.L M400 USB external decoder - resolution curve @LDAC48 Lineout
LDAC test
16/44
24/48
24/96
-101.6
-104.1
102.5
114.3
0.00057
0.00197
0.00091
0.00538
0.00256
0.00215
-94.4
-99.2
-99.3
Shuangmu Sanlin S.M.S.L M400 USB external decoder - frequency sweep @LDAC 44.1
Shuangmu Sanlin S.M.S.L M400 USB External Decoder - Frequency Scan @LDAC 48
Shuangmu Sanlin S.M.S.L M400 USB external decoder - frequency sweep @LDAC 96
The performance of LDAC is also normal, and the work is stable in close proximity. However, from the perspective of objective indicators, the signal-to-noise ratio of about 104dB under 24bit seems to have a slight gap with our commonly used test platform, which should not be the best state of LDAC, but it is not easy to detect in use.
Haibei's UAT test results are shown in the figure, and at present, this result is really a bit too bad. As shown in the figure, the frequency scan of 20Hz-48kHz at the 96kHz sample rate starts to be distorted from 14kHz under the high-quality connection, the higher the frequency, and the brightness of the line is significantly increased? That is, the level is significantly increased. In partial connection quality mode, the situation is even worse. Look at the 44.1kHz sampling rate 20Hz-20kHz scanning, more weird, look at the waveform chart, what is this shape? What's even weirder is that if we turn off LDAC in the Android settings, the situation will be even worse.
Shuangmu Sanlin S.M.S.L M400 USB External Decoder - Frequency Scan 44.1kHz@Hiby UAT Bluetooth
Shuangmu Sanlin S.M.S.L M400 USB External Decoder - Frequency Scan 96kHz@Hiby UAT Bluetooth
The previous paragraph is the connection priority setting, and the latter paragraph is the sound quality priority setting.
Shuangmu Sanlin S.M.S.L M400 USB external decoder - frequency sweep 96kHz@Hiby UAT Bluetooth LDAC off
Of course, regarding the Bluetooth UAT test, considering various problems such as the receiver, the transmitter and the software cooperation at both ends, it is not certain that this is the problem of the UAT. But in the test, we replaced multiple phones and forced off the surrounding 2.4G WiFi, which of course certainly had nothing to do with the strange shape of the test results. Originally, we were very interested in the UAT test, but we can only have the opportunity to do it later, hoping that its performance will not be so weird.
Subjective hearing
In the subjective hearing test, we left the part with SMSL's own SP400 headphone amplifier for a few days later. Today's main talk about the performance of the SMSL M400 decoder with the speaker system. The test speaker section includes AirPulse's A100 and New Dirk A600 amplifiers + Scanspeak D6620 treble + Vifa ne180w-08 6.5-inch mid-bass bookshelf box combination as a reference. The contrasting sound source chose mr1 and element-M of the sound, although the two are different in function and positioning, but we only compare the sound style of the CS4398 DAC and ESS 902x Pro DAC with the high-end positioning.
<b>Overall impression:</b> Regardless of the I/V design of the M400, it makes us really feel at ease when it opens, the dynamics of the M400 decoder in the intermediate frequency and high frequency parts are very different from the previous voltage type AK449x, the sound lines are bright and extreme, even slightly excessive, and the stereoscopic prominence of the vocal performance is even a little excessive. There is no longer the sound drifting sound on the AK449x due to lack of dynamics. Instead, however, there is a rare true neutral or even youthful, ostentatious style in recent years. In the entire midrange area, it is not so thick, which is not surprising, after all, AKM was also known for its light elegance in the AK4397s. In the low-frequency diving part, it is also a good performance.
<b>Treble performance:</b> The high pitch of the SMSL M400 is straightforward and brash, no longer the so-called delicacy on the AK449x [at least 4497, 4495, 4490], the sound has become three-dimensional, the dynamic performance is sharp, the transient is quite sharp, and in recent years, everyone has begun to pursue "warm sound" in the environment, and it is really rare to hear such a style. It's a bit of a feeling of hearing the AK4397 sound card, PCHiFi in the early days. This treble is not the Pursuit of Extreme Detail in the EXTREME HIGH Frequency section under the Chord Hugo series, and in the EXTREME HIGH Frequency Section, the M400 of the AK4499 does not have much deliberate modification. Instead, the sound dynamics in the high-frequency, mid-high-frequency areas are very good, the transient speed is fast, and the sound is somewhat exaggerated, and even some are brittle. There are some exaggerated "British sound" flavors, and unlike the traditional listening style and the coldness of Japanese sounds, it still has very good lines and dynamics.
Such a high note we originally worried about with the aluminum belt treble will not be too hard, too hard to be too brittle? There is no problem with the actual collocation performance. But the style is definitely completely out of the so-called warm sound system, its treble knot image position is more advanced, for violin strings, treble brass instruments and other performance textures have exaggerated components, the sound is obviously more gorgeous, the lines are slightly abrupt. However, due to the high level of quality, there will be no hearing problems such as burrs and particles. When paired with the treble of plucked instruments, the speed is slightly faster, and the exaggerated sound density may make some of the originally weak recording noise be relatively amplified, such as the before and after noise of the touch strings, and some so-called rosin sounds of stringed instruments in some recordings, which are very distinctive, but may be slightly blunt.
Such a sound style, for the recording itself with too much MSG will not be very suitable, and for more rigorous recordings will sound like high details are good, but slightly exaggerated, bright, density than imagined relatively excessive. However, from the current point of view, with the speaker system, as long as the quality of the tweeter is guaranteed, the problem is not big. However, pairing with ear amplifier headphones may encounter problems.
Whether it is the MR1 that already has a modified component or the ESS 902x Pro series, in front of the AK4499 M400, it can be said that it is obviously restrained and warm. However, in terms of density and dynamics, the M400 is stronger than the MR1, which is closer to the ES9028Pro's Element-M and has a stronger density. However, from a high-end decoder, it can only be said that the M400 treble is very stylish, and it is still worse in terms of beauty and level.
<b>Midrange performance:</b> Although we can be sure that the midrange and vocals of the AK4499 M400 have finally become stereoscopic, clean, solid, and have a very good dynamic, it is still not a thick, full, warm style. For the expression of young female voices, such a style obviously strengthens the sound of breath, the saliva song is really enhanced by the saliva sound, and the so-called "mouth shape" also sounds very different. But the dynamics are good, and the sound stereo is always much stronger than all the previous AK449x fluttering pretending to be warm. Relatively speaking, such a style is also not very suitable for recordings such as saliva songs, which cannot be blamed on decoders, but on recording MSG is too heavy. For mature female vocals, the thickness is relatively insufficient, but the sound tension, dynamics, lines, and knots are very good, and the style is indeed slightly younger. The performance of the male voice, even if it is a mature male voice, the strength and resolution of the voice are very good, the thickness is insufficient, and it is light. Everyone should understand that there is a big difference between the lightness brought by the thickness and the sound not solid caused by the serious lack of dynamics. It can be basically confirmed that the AK4499 under the M400 performance should have changed the obvious lack of dynamics before the AK449x.
In the performance of large dynamic works such as symphony, its image position is relatively backward, mainly because the thickness of the low part of the midrange is not enough, or it is relatively insufficient, and the middle and high frequency articulation part is obviously bright. At present, it is speculated that the equilibrium of this part may be optimized in the I/V and LPF parts, and it may be that the M400 is doing something exaggerated. Of course, for such a performance, it is quite suitable for symphony, after all, the typical EQ of the symphony is also tuned in this way. Its mid-range and mid-high frequency dynamics are very good, full of strength, and the sound is more ostentatious in the mid- and high-frequency areas, which is slightly too gorgeous. Good control in the mid-range area. The sound tension is measured, even better than the dynamics and control of the MR1.
<b>Bass performance:</b> The M400's mid-bass part of the articulation seems to be the most obvious flaw in the whole machine, the cause is unknown, and it is estimated that there is room for optimization, not the problem of the DAC chip itself. In the deeper part of the low-frequency dive, there is a good strength and depth of the dive. It should be noted that this part of the detail may require a large caliber mid-subwoofer to perform, like the A100 should not be a good reflection of its advantages. Compared to the ESS 9028Pro's equipment, the dynamics of the deeper parts of the low-frequency dive are comparable, with slightly weaker force and slightly faster deferred transient speeds. The thickness of the low and medium frequency parts is larger, and it is also weaker than MR1, which also causes its overall hearing to be less thick. Of course, this may also be the style that AKM has always preferred. In addition, it seems that AKM devices should not be expected to express low frequencies like ESS or PCM179x, which is almost zero. In the very dynamic, loud pressure burst low frequency, the M400's low frequency dive is satisfactory, and the details are also good. Better than the previous evaluation of the national brick AK4497/ AK4493 is no problem, and its medium frequency can basically be considered that AK4499 returned to normal dynamic performance capabilities, and voltage type AK449x has a difference. It's just that in the low and medium frequency parts, we still need to work hard to optimize.
<b>summary</b>
The first time I heard the AK4499's decoder, the SMSL M400, seemed to have a taste of the AK4397 sound card more than a decade ago, when PCHiFi was in its early days. The sound is straightforward, pursuing lines, dynamics and density in the high and mid-high parts. The mid-frequency does not pursue a very warm thickness, but it is straight, three-dimensional, clean, and has better control. Unlike the so-called jerky monitoring style, the AK4499 M400 still has good tenacity, and does not have problems such as glitches and unpleasant graininess due to too strong high-pitched density and flamboyant style. It is just that in the performance of phonograms that already have heavy tastes, it is somewhat unsuitable. For normal recording, the M400 will be more youthful and energetic, slightly brighter.
Although today's evaluation is the first time we have heard the sound of AK4499, we still hope to be able to optimize in the low and medium frequencies, so that the thickness is slightly enhanced, and the density of the middle and high frequencies is converged, not too crunchy.
Also because it is the first time we have heard the sound of AK4499, so the trend and style analysis is only the beginning, and it is certainly not accurate. But we have seen the design of AKM external I/V that has been missing for more than a decade, and hope that we can hear the subjective sound changes and I/V external design, and also hope that we can hear better AK4499 through I/V, LPF and other optimizations. More hopefully, AKM's DAC chip, at least on music-listening devices, will introduce more external I/V versions of the AK449x's low-end model. After all, for music appreciation, that is, a D/A core parallel, the difference between 110dB and 140dB is really not as important as the I/V design, not to mention that AKM in the AK449x model may show such obvious shortcomings on hundreds of devices in the market?