Sony WF-C710N FCC Teardown

The FCC internal photos of the WF-C710N have become available. So let us see what secrets the new model is hiding and how the design compares to the WF-C700N. While this not a step by step teardown like 52Audio's. we are able to see all of the major components and parts inside. Check out the announcement post for more details on the headset.

This first photo does not really show much, to be honest, but I suspect we have clips and tabs holding the case together, like in the old model. The case battery, as with all of Sony's earbuds, is underneath the plastic piece which the PCB sits on. While it is difficult to tell from these photos, I feel there is space for a wireless charging coil. Considering the new LinkBuds Fit did not receive wireless charging, it makes sense why the WF-C710N did not either. The battery/PCB assembly is screwed into the underside of the middle piece (top left corner).

The case PCB size has decreased in size when compared to the WF-C700N. We now have two ICs, one on each side, and 2 charging pins per earbud, 5V and ground. Unfortunately the photos are not clear enough to make out the writing on the chips. Sony still uses the old HDX-#### model names on the PCB, rather the YY code designations.

The board also has a date code, 2434, meaning 2024, week 34, or the second last week of August in 2024. Not sure if this is just for the certification prototype, or if Sony (actually Cresyn) started production around the same time for the retail units.

A major change is the addition of a battery connector on the board, where previously the battery was soldered directly to the board. There are now 3 cables connected to the battery, just like the new WF-C510, and Sony's other newer earbuds. From what I have read online, the third wire is for the thermistor, which monitors the battery's temperature when charging.

Neither the WF-C500 nor WF-C700N had this extra third wire, so I am unsure if the case batteries had any temperature monitoring. I am sure there is charge protection on the case batteries but perhaps not related to temperature, just current? This could explain the recharging issues users have experienced when recharging with AC adapters. Sony does recommend to using AC adapters with less than 13W.

Removing the top of the earbuds, we can see the touch sensor and wireless antenna on the underside. The top of the main PCB is visible here with 2 pin connectors for the touch sensor and antenna. The wind reduction structure is visible just under the touch sensor, and seems identical to the one seen in the WF-C700N. The previous model used a physical button (see photo below), but the general design is similar between the 2 models.

Sony WF-C700N

Removing the PCB and battery, we can see there is a foam spacer (1) between the battery and the flex cable assembly. The voice/feedforward NC microphone is also visible in this photo (2). The flex cable assembly connects to the PCB with a connector.

Removing the earbud PCB, we can see a metal shield covers the main Bluetooth SoC. This shield is soldered to the board. The battery connections (+/-) are the side beside the metal shield.

The other side of the PCB has the wireless antenna contact (1) and the touch sensor contact (2). The flex PCB connection is on the bottom of the board.  Not sure what the other small chips are, while there is support for 360 Reality Audio, I am unsure if head tracking is supported in this model.

The WF-C700N lacks a metal shield, but does use a similar flex cable connection. Removing the metal shield, we can see the Bluetooth SoC.

Sony WF-C710N PCB

The biggest change, is Sony switching from a midrange Airoha AB1562A Bluetooth SoC, to the Mediatek MT2822M. This is the Sony V1 found in the WF-1000XM4, LinkBuds, LinkBuds S and ULT Wear. There is no mention of the Sony V1, or any new Bluetooth chip on the WF-C710N product page. The WH-XB910N also uses this same chip, but there is no mention of the V1 on its product pages either.

In my opinion, Sony should definitely mention the V1 on the WF-C710N product pages. Granted it is not the new V2, but still features improved performance over the previous Bluetooth SoC found in the WF-C700N.

Below is the Sony WF-C700N PCB for comparison with the Airoha AB1562A Bluetooth SoC. The layout is similar but the WF-C710N lacks the battery protection chip seen in the WF-C700N. This chip is also absent in the WF-1000XM4, LinkBuds and LinkBuds S. The Sony V1 has the battery protection built into it from what I understand, so this explains this extra chip is absent. I have more details on the V1 here, and here.

 

The main differences between the Airoha AB1562 and Mediatek MT2822 (AB1568), is the addition of a host processor, the ARM Cortex-M4, which pairs with the same DSP Cadence HiFi MiniAudio Engine DSP coprocessor. The embedded flash is 8MB, versus 2MB/4MB. I suspect the MT2822 is also a newer chip, and more efficient, seeing as the internal battery capacity stayed the same but the battery has increased.

Sony WF-C700N PCB

The flex cable assembly in the WF-C710N is similar to the WF-C700N but with additional components. 

1. Proximity sensor
2. Voice/Feedforward NC MEMS microphone
3. Feedback NC MEMS microphone
4. Driver contacts (these will be soldered in the actual retail unit 
   

Just like with the charging case PCB, we also have a date code on the flex PCB, 240809, if this is YY-MM-DD, then this would be August 9th, 2024. The flex PCB photo does confirm that we have 2 NC microphones inside the earbuds as mentioned on the product page. The extra NC microphone, together with the MT2822 (V1), should help improve the ANC performance versus the WF-C700N. Looking forward to comparing the new model to the old.

Finally the batteries. Sony will again use 2 suppliers VDL and High-Power for both the earbuds and the case batteries. The case battery is 500mAh at 3.85V.

VDL earbud battery

High-Power earbud battery

The High-Power batteries have Zenipower written on them, so I guess they are a part of High-Power? The case battery model is 772030 for High-Power, and the VDL the model is 772130. both batteries are 3.85V 500mAh.

While we do not have an expanded component view from Sony's product pages, I did find this in a certification filling.

Always a pleasure to see how it all goes together. And with that, this ends the teardown.

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