BTI-031 Sky Wing: an aptX HD Bluetooth transceiver with a headphone amplifier at a bargain price!

It is becoming more and more obvious that receivers with aptX and aptX HD codecs for Bluetooth connections are going to secure themselves a strong position as Hi-Fi elements on the market with sounds results that won’t deter music lovers. And this, at prices that could be considered ridiculous, like this BTI-031 Sky Wing.

By Philippe DAUSSIN | Testing Ground | May 30, 2018

In several instances, we have had the opportunity to present you with testing grounds of Bluetooth receivers, and also of wireless Bluetooth headphones, compatible with the Qualcomm-CSR aptX and aptX HD technologies, and whose sound results have always impressed us.

These codecs, one limited to CD-quality files (aptX) and the other to 24-Bit/48 kHz Hi-Res files (aptX HD) use non lossless compression algorithms, let’s say, because their efficiency is such that the difference of restitution between the non-encoded files and the encoded ones is rather hard to perceive.

The following testing ground will be devoted to a small aptX HD Bluetooth transceiver that we acquired on the Internet under the reference LEVN BTI-031, but it would seem that it is instead built by the manufacturer Sky Wing, which offers other models that are non aptX.

An aptX HD Bluetooth receiver, it also allows you to use it as a Bluetooth transmitter and to share audio files by encoding them into aptX or aptX HD if it establishes a connection with a receiver compatible with one codec or the other, and can be used simultaneously with two receivers.


The BTI-031 takes the form of a small square black box with very round angles whose top section is composed of a light grey belt, a central key press (also called Multi Fonction Button or MFB) enabling the powering of the device or the launch of a pairing, the rubber intermediate zone allowing you to act on four command keys, volume up and down and skip to the previous and next file. Another finish, more feminine and beautiful, is also available.

At the bottom, you can see a small light guide for the status indicator LEDs and below, on the bottom side of the box, the micro USB socket to use and charge the battery. You can also see the switch allowing you to choose between the receiver and transmitter modes, but know that the transmission with be done from analog signals.

These signals will be coming from the Jack plug, which is also used for the reception and can be linked to a Hi-Fi system’s auxiliary input or to power a pair of headphones. You will also notice the metal clip-on (which is detachable) that you can use to attach the BTI-031 on your clothes.


The small double-sided circuit board whose outline is somewhat crooked welcomes on its top side the command keys and the three small status indicator LEDs, as well as, next to the Jack socket, a SGM3717 (U3) circuit from the manufacturer SGMicro. This circuit, controlled by the TX/RX switch, is composed of two analog commutators that will direct the decoded signals toward the outside in reception mode (RX) and the analog signals coming from a source toward the CSR module in transmission mode (TX).

On the other side the micro USB plug used for the power supply as well as the charge of the 3.7V/170 mAh battery is located. Just next to it, and before the Jack socket, you will find a Diodes Incorporated PAM8908 headphone amplifier which will also be used in line mode. The circuit marked U2 is probably overseeing the charge of the battery.

The central part is occupied by the Qualcomm aptX HD Bluetooth module equipped with a CSR8675 chip. Above it you can see the microphone enabling phone calls as well as another SGM3717 circuit composed of analog inverters to cut the music and commute lyrics.


For the occasion, this is our Sony Xperia XZ1 smartphone that will act as an aptX HD source by encoding albums streamed with the Qobuz application for Android. And we haven’t chosen the easiest route, since it’s the very personal interpretation of Tchaikovsky’s Violin Concerto performed by the MusicAeterna ensemble and Patricia Kopatchinskaja on violin conducted by Teodor Currentzis.

Once again, we can only applaud the results obtained via a Bluetooth connection with the aptX HD codec, which allowed us to hear this interpretation almost the same way we know it, with its subtleties, the bow strikes of the soloist that are sometimes almost grating, sometimes lively and sharp, not forgetting the orchestra’s dynamics and bandwidth that are always present. We have also listened to the finale of this concerto with our Oppo PM-3 headphones and the sound results, power, frequency response, dynamics, and accuracy of restitution were also there, and at no time could we notice that we were using a Bluetooth connection.

Maybe it wasn’t the best choice to listen, under a beautiful sun and with headphones on our ears, to You Want It Darker from Leonard Cohen’s eponymous testament album, but this piece of music is more or less the polar opposite of the previous one, opposing to this one a certain darkness and languor that the BTI-031 reproduces, we won’t say happily, but with as much talent.

We will remind you that in order to benefit from the aptX and aptX HD encodings, you will have to use a compatible smartphone and that an aptX or aptX HD receiver won’t bring any improvement if used with an Apple smartphone.

To conclude, if you do not wish to part with your wired headphones but you wish for it to not be plugged into your dear smartphone (compatible with aptX HD of course) anymore, you can opt for this small receiver, which is as cheap as it is efficient.

Manufacturer’s website

R.R.P.: less than 30 euros (sold online)


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