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Testing Ground

S.M.S.L Icon: an elegant Lightning DAC with a great sound performance!

By Abigail Church |

Intended for Apple smartphones and tablets equipped with a Lightning connector, the new Icon DAC from the Chinese manufacturer S.M.S.L, even if it complies with Apple’s demands and, in some way, with the normalized sound of the computer giant, is rather attractive with its successful design.

It’s been some time since the arrival on the market of DACs and headphones equipped with a Lightning connector, which allows them to be directly plugged into an Apple smartphone or tablet also equipped with one. It was around the release of the iPhone 7 and its Lightning to Headphone Jack adapter.

Until then, the few MFi (Made for iPhone/iPod/iPad) compatible DACs—the predecessors of this new generation if you will—that we had seen were generally equipped with a female USB A socket in which was plugged the standard Lightning cable with a male USB A plug, the USB interface chip being for its part a specific model that is also MFi compatible, as we had observed in the testing ground of the Denon DA-10 DAC.

It still left some leeway to the DAC manufacturer, as we’d seen during the testing ground mentioned above, and avoided the use of the Camera Kit like with the OTG DACs that can run on iOS, a scenario that could of course lead to some clutter.

With this new race of MFi DACs that has just appeared, we can say that the manufacturers have almost gotten rid of all initiative regarding electronics, since it is set by Apple and only the design and a small part of the controls—and some action on the sound—are magnanimously left to their goodwill by the Regent who still retains their grip on its sound kingdom, most probably collecting some royalties in passing for the adhesion to the MFi Program, to which belongs this S.M.S.L Icon DAC that we are now about to present you.


Presentation

For sure, this S.M.S.L Icon Lightning DAC is completely different from the Apple model. Its beautiful box in aluminum, which has been machined by a Computer Numerical Control device, displays a nice modern outline and a pleasant grey color, and is provided with discreet keys allowing to set the volume, manage the calls and launch the SMSL Player application, which is however nothing special, as you can see on the pictures, except that it obviously handles Hi-Res, which is not the case of the Apple player. Moreover, the length of the cable (30 cm, or 1 ft.) will allow you to leave a bit of slack between the smartphone/tablet and the DAC.


You can notice two little holes in the box, the upper one is meant for letting the sound pass towards the microphone and the bottom one to let the light emitted by the blue LED—located on the printed circuit board—indicating that the device is working.

Manufacturing

The electronics of the S.M.S.L Icon DAC is compliant with the recommendations of the MFi Program. On the right side of the circuit, you can see the interface module with the Lightning port and next to the 3.5 mm Jack socket, there’s a Cirrus Logic CS42L42 chip, a 24-Bit/192 kHz coder-decoder, a low-power model equipped with a 2 x 35 mW in 30 Ω headphone amplifier, and whose internal structure is rather complex.


The CS42L42 includes a digital-to-analog converter for the microphone, and the signals can be filtered in a windy situation by a windnoise filter or even benefit from some equalization. Signals coming from the microphone are conveyed after their digitization toward the Lightning port to be sent toward the mobile telephone network and they are also combined with those coming from the Lightning connector; the whole is then converted into analog signals that can be heard through the headphones. Sampling rate converters, which can be bypassed, are also present on the path of the digital signals, whether incoming or outgoing.

With lots of difficulty, after browsing through dozens of Internet pages and almost before the deadline of this testing ground, we finally managed, thanks to our stubbornness, to get hold of the CS42L42’s datasheet—a large piece of eighty pages classified as ‘Confidential’—which allowed us to know a bit more than the scarce information provided by the Cirrus Logic website about this chip and to tell you about what we thought was relevant.

We learnt in it that the headphone amplifier is a class AB model whose power supplies can be modulated depending on the incoming signal, the adopting a class H working, and that its power can be limited, which explains how the one provided by this S.M.S.L Icon DAC turned out in our listening sessions to be superior to the one of Apple Lightning to Headphone Jack adapter.

It’s also worth noting that this CS42L42 chip is smart, as it detects the presence of a headphone and its type, with or without microphone, activating if there is one its digital-to-analog part in order to allow a phone conversation and that it possesses, in addition to a standard I2S interface, a Soundwire interface, which, incidentally, led us to discover this recent interface (2014) from the MIPI Alliance (MIPI : Mobile Industry Processor Interface), founded in 2003 by ARM, Nokia, STMicroelectronics and Texas Instruments, and which includes Cirrus Logic and Apple among its many contributors.


On the other side of the circuit we find the microphone encapsulated in a small metal box resembling an oscillator, the keys, as well as the microcontroller whose part of a code is left—even if it’s still have to respect the MFi program—to the liking of the manufacturer (MCU example code shows how to quickly develop a product that complies with MFi requirements, as the MFi Digital Headset Reference Design) reveals, S.M.S.L implementing the possibility to launch the SMSL Player application from a button on the Icon DAC.

Sound

With this Qobuz app for iOS, the sound reproduction offered by the S.M.S.L Icon DAC of Henry Wood’s Fantasia on British Sea Songs is sharp, precise and spacious, qualities which manifest in particular in the first title, The Saucy Arethusa, in which we hear all the small details, such as the discreet triangle, even if the power isn’t great (with our Oppo PM-3 headphones, we are a bar away from the highest level).


The languorous Tom Bowling proves to be rather singing and, in a quiet environment, you don’t have to listen carefully to follow the smooth violin singing and to perfectly hear the pizzicati from the double basses. As for the mischievous Jack's the Lad, the S.M.S.L Icon DAC perfectly restitutes the dynamic gradation of the scene, which burst out in a frenzied finale without any harshness or saturation, while the beautiful title Home Sweet Home is reproduced with a tenderness devoid of excessive sentimentality, and the bravura pieces that conclude the work, See the Conquering hero and Rule Britannia let effortlessly burst out—despite the rather modest power of this DAC—their imperialistic-patriotic fervor through powerful brass instruments and the clanging of cymbals that never put our eardrums at risk.

It also goes very well with Carl Orff’s album Carmina Burana performed by the London Philharmonic Choir and the London Philharmonic Orchestra conducted by Hans Graf (24-Bit/44.1 kHz Hi-Res version) whose every variety of timber—like the bell starting the Ecce gratum with a striking impact and very pleasant resonances—benefits from a faithful restitution while the S.M.S.L Icon conforms to the slightest difference in level as well as to the biggest ones, of which there’s no lack of in this work, but it would seem that this DAC is somewhat less at ease than previously with the impressive orchestral and choral mass, and it requires you to turn the volume down a bit. There is no doubt that the rather weak amplifier power shows its limits in such a case, which is not an easy one nonetheless, but anyway, the sound results are still more than good.

You don’t have to turn up the volume too much to get rather important sound levels while listening to the title Out Of The Black from the album Royal Blood in which the decibels are unleashed in a saturated electric mood, of which the S.M.S.L Icon DAC doesn’t seem to have any difficulty reproducing the guitars’ distortions by clipping with power and consistency, but as for appreciating other parameters… Still, this sound restitution holds its own and the DAC’s amplifier knows its stuff, as they say.

To conclude, with the S.M.S.L Icon DAC, we are in the presence of a small Lightning DAC displaying at the same time a very pleasant design and more than good sound performances, with a slightly higher power output than its all-white counterpart from Apple, a little addition that proves to be really nice and allows you to enjoy even more your favorite music!

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We would like to thank Audiophonics for lending us the S.M.S.L Icon.

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