Teardown AmazonBasics Nano Bluetooth Speaker

2017-07-24 | By All About Circuits

License: See Original Project

In this teardown, we will examine the AmazonBasics Bluetooth Speaker to see how manufacturers continue to reduce the size and cost of devices that once were thought to be impossible.

The Speaker

The speaker is a small plastic housing that appears to contain two speakers (one either side). The outer perimeter of the speaker has a rubber handle and buttons to operate the device. The buttons include volume adjusts up and down, and also the function button for turning the speaker on. The perimeter also has the micro USB B connector that is used to charge the unit.

The various buttons on the speaker

The USB port

Pulling the rubber away from the unit was difficult and suggests that the rubber is placed in before the unit is put together. However, there are no visible screws found on the speaker so how this unit was put together remained a mystery until it was finally opened.

Removing the rubber reveals the tactile switches on the side

The USB charging port is revealed in more detail

A long time was spent on trying to find some opening technique but this proved futile. One attempt made was to use a drill press and attack some of the internal cylinder structures seen in-between the small gap around the perimeter. However, this did not work and so more drastic measures were taken. A small saw was used to cut the internal parts to free the two halves with success. A word of caution; this device (and most like it), use lithium-ion batteries and rupturing one can cause fires so be careful.

Drills don’t work here!

It was originally thought that the device had two speakers either side but upon gaining access to the internals it turned out that only one speaker was active. The other speaker was just a diaphragm but this may be useful by also producing sound when the internal air pressure changes due to the powered speaker operating.

Turns out that there is a false speaker!

With the device opened, the PCB and other parts were revealed in all their glory. It turns out that the unit is held together via screws yet there are no visible entry points for those screws. Therefore, it is most likely that these units are pressed after being produced to create the speaker pattern seen on the outside.

The internal parts revealed

The PCB – Topside

The topside of the PCB reveals an interesting mix of through hole, surface mount, and modular parts. Large capacitors are of the through hole variety whereas controller ICs use surface mount packages.

The topside of the PCB

The IC in the center of the PCB uses an MLF package and has the identification of 2810D0. A datasheet for the part cannot be found however its function can be deduced by looking at what it connects to, the sizes of those connections, and the nearby components. This IC contains various capacitors connecting to IO pins, but one trace, in particular, is the top right trace that connects to the electrolytic capacitor. Another interesting feature is the two ferrite parts connecting the speaker port to the IC. Therefore, this implies that this IC is a driver for audio equipment.

The suspected audio driving IC

The speaker also has an LED indicator that is housed in a small piece of shrink tubing. As can be seen in the photo, the unit was still operational during the teardown. This picture also shows the various switches and a few stitching via in the flood planes.

The glowing LED indicator and the switches

The module (blue) found on the PCB is the unit responsible for Bluetooth transmission. The top of the module has no ground plane or solder mask to maximize the effectiveness of the PCB antenna. The main IC on the module has the identification of BK8000L which is a Broadcom device that is designed to produce audio signals. The device supports serial AT commands, so this device can (in theory) be hacked by identifying the RX and TX and connecting it up to a serial port on a computer.

The Bluetooth Module

The BK8000L IC that handles Bluetooth connections and audio processing

The second IC on the module is identified as a BoyaMicro 25Q40ASTIG which is a serial flash NAND device that contains 4Mbit of data and has dual/quad data access capabilities. This device on the module will most likely hold information such as network and device configuration so when the device loses power, it will not forget user configurations.

The serial flash device BoyaMicro 25Q40ASTIG

PCB – Underside

The underside of the PCB shows no components and only a single Lithium-ion battery. The lack of components on one side helps to keep manufacturing costs down as well as complexity. The battery used here has a capacity of 1.5Wh at 3.7V (430mAh).

The lithium-ion battery stuck to the underside

One nice feature that hackers will really appreciate is the use of many test points and labeled pads that include serial connections and JTAG. Since these pads are very close to the module and the lack of any other controlling ICs, it can be assumed that these pads connect to the Bluetooth module.

The labeled pads under the main microcontroller

More labeled pads

Summary

This Bluetooth speaker demonstrates many manufacturing techniques with simplicity and cost in mind. The use of mainly surface mount parts with all components on one layer helps to keep costs down as pick-and-place machines are only used once. This also gives the PCB the opportunity to use wave soldering for the through hole parts which also helps to keep production costs down. The lack of screw holes is something that I personally have not seen on a unit that uses screws yet and hopefully it does not become the norm in product design as they make teardowns nearly impossible!