Sony INZONE Buds FCC Teardown

I am sure many of the blog's visitors noticed I did not cover the new INZONE release. This was mostly because any posts I made would have been drowned out by the coverage by the main tech sites. Besides, I do not get any review units, so I would just be reposting the press release. So instead I waited for the FCC documents to become available so I could make this teardown post. I do hope 52Audio performs a full teardown as it will be a lot more detailed than what I can present here.

Sony Japan does have an interview with the engineers but very little tech info is covered in the article. One small detail revealed is that the Bluetooth chip is a custom one from Sony, the L1. The chip is low voltage, high efficiency and has a reduced operating current. Below is a close up shot of the main PCB from the Sony engineer article.

Now turning to the FCC photos. Not everything is revealed in the documents but we do get a much better look than in previous filings.

In the first photo we have a good view of the underside of the main PCB. We can see 2 contacts on the right side, one for the antenna, and the second for the touch sensor. We also have a hole for a mic, which is most likely used for both noise and voice pickup. There is also a connection for a flex PCB at the top.

The next photo shows the antenna/touch sensor module in focus. We can see a hole for the mic in the bottom, along with the antenna contact (lower) and the touch sensor contact (upper). I believe the WF-1000XM5 have a similar design for its antenna and touch sensor.

Here we have the inside of the case and part of the charging PCB. There does appear to be some room where Sony could have added a wireless charging coil, but perhaps we will see a higher end model in the future with this option. Unless Sony deems wireless charging not fast enough?

Next up, we have the main PCB inside the earbuds. It is dual side with the main Bluetooth chip shielded to minimize any outside interference. We can see one of the MEMS mics, which we saw earlier in the photo from Sony I already revealed the main wireless chip in an earlier post, but it is always good to see a physical confirmation. The chip is the CXD3277, or D3277 here. This follows the same pattern as Sony's other chips, like the S-Master HX, which is labelled as D3778 but has a model number of CXD3778.

I believe the earbuds use a dual NC mic setup (like the LinkBuds S), even though I cannot find any mention of this in any of the product pages. If anyone can find a reference to dual NC, please let me know below in the comments.

If we remove the main PCB, we can see one of the flex PCBs, along with 2 magnets, one at the top and one lower down. At the top, we can see the flex PCB connector which attaches connects to the main PCB.

Here is the first flex PCB with the charging pins and battery contacts I believe. There are only 2 charging pins, like in the WF-1000XM5.

Next is the second flex PCB with the second NC mic and driver contacts.

I am only posting the photos of the left side since the right side is identical except mirrored. The microphone at the end of the flex PCB is probably near the main driver, but the FCC photos do not show this.

Next looking at the charging case PCB.

Here we can see the battery connector in the top left, the pairing button bottom left, and the USB type-C port in the middle. 

Flipping to the other side, we can see a ribbon cable connector and a main controller chip, the NXP KL28, which is the same chip found in the WF-1000XM5 charging case.

There is a second smaller PCB in the case, which has the front LED and connections for the charging pins.

And here is everything connected. As I mentioned earlier, we only have 2 pins, a ground and the USB 5V bus.

We rarely get to see the batteries in these FCC teardowns, but we are in luck and Sony has included both the case and the earbud batteries in the documents.

For those wondering if Sony has moved on to another company for their earbud batteries, it appears they have not. The INZONE buds use a 3.86V 0.36Wh Zenipower coin cell battery. This is around 95mAh. The battery model is Z55FH. This is also the same battery used in the WF-1000XM5. How do I know this, well the design matches, but then Sony also revealed this in their engineer interview:

At the same time, the power of the battery itself is also important. "INZONE Buds" incorporates the new high-capacity battery used in the latest completely wireless headphone flagship model "WF-1000XM5."

Unfortunately, I do not have the measurements of the battery, but by going off the FCC photos, it does look like the battery is 12mm in diameter, so matching a 12.1mm that is the industry standard. We do not have the height, so that could have changed. But if the size is the same as the Z55H, then theoretically one could buy 2 Z55FH batteries and swap them into the WF-1000XM4. This would help with battery life.

Moving to the case battery, we have 2 suppliers, VDL and High Power. Unfortunately the FCC document only shows the capacity of the VDL battery.

We are looking at a 3.85V 450mAh Li-ion battery, model number is 731734. It is rated up to 4.4V.

Finally we can have a quick look at the USB dongle.

And here is a close up of the PCB and the main Bluetooth chip, an Airoha AB1565. See my write up on the Sony V2 chip for details on the AB1565.

And with that, this concludes this FCC teardown. While not a complete teardown, we did discover the new Z55FH Zenipower battery, which is also used in the WF-1000XM5. We know that the INZONE buds use 2 NC microphones, and that the USB dongle uses an Airoha AB1565 chip. I suspect the Sony L1 (CXD3277) is a custom Airoha/Mediatek chip, but we will never know for certain. 

If anyone notices anything else from these photos, drop the information into the comments.