Sony LinkBuds Teardown

The Sony LinkBuds were announced only last month and we already have a teardown by 52Audio. Check their article out for the full teardown which features a lot more detail than I will be posting. 

                    

So beginning with the case PCB, we can see Sony has decided to solder on the battery cables like in the WF-C500. While not a major issue, replacing the battery would require more work and tools than in the WF-1000XM4, which has its battery attached to the board with a connector.

There is a connector in the top left, but this is for the extra PCB which signals to the headset to either connect/disconnect to the paired device when the lid is opened/closed. The USB type-C port is not centered on the board since to the left is a reset button.

The other side of the PCB has the main controller chip and the charging pins. The main chip is the K32 L2B microcontroller; more information about it can be found here. Interesting to see the model code printed on the board, YY2953, rather than the model name, WF-L900 like in other models.

Comparing the internal battery, we have a type 621733 lithium ion, with a capacity of 300mAh/1.11Wh. If this battery looks familiar, that is because it is the exact same battery that is found in the WF-C500 charging case. For the rest of the case teardown check the source.

Now moving onto the earbuds themselves, both halves in the driver unit and main body are glued together.  As seen below, the black substance does not surround the entire opening, so this is probably not for IPX4 resistance but to hold the pieces together (in addition to glue). There is also no mesh on the holes so best to keep any dirt and water away from them. The little holes do face the ear canal, so it is possible that the hole could get clogged up with dirt and ear wax.

Opening up the main body, we have a ribbon cable connecting the cover to the rest of the unit. So be careful when opening this part so as not to rip/damage the cable.

On the inside we have the battery which is held inside the earbuds with a plastic surround. This is probably to keep the battery in place. Unfortunately the consequence of this is that the battery looks to be smaller than in other models.

Click for a larger size

The battery is a Zenipower brand again but a different model, Z32H. The capacity is 3.85V 0.12Wh, which is around 31 mAh. Looking at the other Sony earbuds, the WF-C500 is around 70 mAh and the WF-1000XM4 is around 75 mAh. 

In the engineer interview post, I was wondering if the lackluster battery life was because of a smaller battery and it looks like this is the case. The capacity is around 44% of the WF-C500 yet the battery life is about 55%, so I suspect the MT2822 in the LinkBuds is a lot more power efficient than the Airoha AB1562M. Shame Sony did not opt for a slightly larger battery, perhaps 45-50 mAh. I am curious if a larger battery would fit if the plastic surround was removed? Anyone wish to test it out on their earbuds?

Now moving onto the ring driver. While we have seen photos of the driver in the Sony Engineer interview post, it was only shown outside of the earbuds, but now we can see it in situ. The black membrane which produces the sound can be seen in the middle. 52Audio measured the driver to be around 13mm.

Taking the driver out of the body we can see how the driver connects to the main body, via 2 small pins, which means the driver is not soldered to the main board. Therefore any repairs/replacements of the ring driver would be rather quick and easy once the cover is removed.

We can actually see where the 2 small pins connect on the main body in the next photo. It looks like the connection is maintained by the force of the plastic cover.

Looking at the inside of the detached cover, we can see one of the PCBs with the positive terminal for the battery. The black plastic piece holds the battery in place and connects to the main body which allows for a secure fit of the cover.

After removing the PCB, we can finally see the call microphone and the plastic piece with the Bluetooth antenna. The microphone does appear to be affixed with what looks to be a lot of glue.

While looking at the antenna assembly I noticed it was very different to the one shown in the engineer interview. It looks like the assembly is attached to the plastic cover with glue.

Top: 52Audio teardown; bottom: Sony Engineer Interview

Comparing the 2 sets of photos. the antenna looks to be the same design with a C shape, but the main plastic piece looks a bit different on the edges. The biggest noticeable change is on the underside with the microphone and board contacts. In the engineer interview post, I even said the PCB contacts did not match up with the contacts on the antenna, but it seems they do on the actual production model. Likewise the microphone looks like it has a lot less glue in the bottom photo. I would guess that the engineer interview part was possibly an engineering prototype or pre-production model.

Now moving to the PCBs. There are 2 connected by a ribbon cable. We have already seen one side with the positive battery terminal, and here they are all in relation to each other.

                     

To save on battery and space, a lot functionality has been ported to the main Bluetooth chip, the MT2822. But there are still other chips like a battery protection chip and an accelerometer present on the boards. 

The main body PCB has the following parts:

1. Proximity sensor
2. On board contacts for driver assembly
3. Charging pins
4. Negative contact for battery
5. Battery protection chip

The other PCB has the following parts:

1. On board contact for Bluetooth antenna
2. Bluetooth SoC - Mediatek MT2822
3. On board contacts for microphone
4. Accelerometer chip
5. Positive contact for battery

Finally a close up of the main Bluetooth SoC, the Mediatek MT2822MA. This seems like it is another variant again, the other being the MT2822SA in the WF-1000XM4. Perhaps this version of the MT822 in the LinkBuds is without the built in DAC/AMP, but this is only a speculation on my end.

There is also a MT2822AA found in the BMS002 Bluetooth module which will be used in the upcoming new wireless speakers. 

But I will write more about this in an update in the Sony V1 post.

Well that is the overview of the teardown, the rest of the photos and details can be found here in the original article from 52Audio. Some interesting surprises, like the smaller battery, a new variant of the MT2822 and the ring driver assembly. While it would have been cool to see the ring driver taken apart, I suspect 52Audio did want to keep their LinkBuds in working order.

If anyone sees anything else interesting in the teardown, leave a comment below. Apologies for any spelling and grammatical mistakes.