Sony WH-CH730N FCC Teardown
Moving to the left side, we have the main PCB, and the USB/3,5mm PCB. The two connections from the right are for the driver (lower), and feedback microphone (upper).
Here is a comparison photo to the WH-CH720N. There does appear to be a lot of less wires in the new model. Such a change would help during manufacturing.
The most obvious change is the one PCB splitting into two. The USB and 3.5mm ports are on their own board, with the rest on the new main PCB. While not clearly visible, the voice microphone may have been changed in the new model to a MEMS type. The WH-CH720N used an electret microphone for its voice mic.
The photo of the voice microphone in the FCC filing is not ideal, but such ribbon cables tend to use MEMS mics rather than electret type in Sony models, so I am confident we are looking at a MEMS type mic.
Why did Sony only change the voice microphone, rather than all of the mics? Could it be related to the addition of LE Audio and LC3 support? The LC3 codec does provide a better quality sound for calls in my testing.
Moving on, we can look at the USB PCB next.
The new smaller PCB has the USB-C port, the 3.5mm port, the ribbon cable connection to the main PCB, and the power button. There are also two LEDs on the left side. The new WH-1000XM4C added a self resetable fuse near its USB-C port, but this is absent in the WH-CH703N.
Moving over to the main PCB.
- Connection from right side
- Voice microphone connection
- Feedback microphone connection
- Driver connection
- USB PCB connection
- Power (GND, VBAT) from right side
- Feedforward microphone connection
It is difficult to compare to previous model as the PCBs are not the same, but the new model features more connectors, like for the voice microphone.
The other side of the main PCB, we can see the wireless antenna (bottom left), and the main Bluetooth chip in the middle.
Zooming in one one section near the top left, we can see a few new chips not found in the WH-CH720N.
A low power stereo Audio ADC (Analog-to-Digital Converter). I am uncertain if Sony is using it only for the voice microphone, or the ANC microphones as well.
An over-voltage Protection switch with programmable over-current protection. This should guard the headset from any dodgy chargers. This might explain the absence of any self resetting fuse near the USB port.
Finally we have the main Bluetooth chip, which I mentioned in my review.
The WH-CH730N has switched to the Airoha AB1585M, from the custom Mediatek MT2822 found in the WH-CH720N. Mediatek has never released any datasheet for the chip, but we do have details on the chip from Sunitec and their BMS002 module.
| Airoha AB1585M | Mediatek MT2822 | |
| Host Processor | ARM Cortex-M33F up to 260 MHz | ARM Cortex-M4 up to 208 MHz |
| DSP | Cadence HiFi5 up to 520 MHz | Cadence HiFi Mini up to 416 MHz |
| Node | 12nm | 22nm |
| Other features | Hybrid Active Noise Cancellation | Hybrid Active Noise Cancellation |
| Max sample rate is 192 KHz and data precision is 24-bit | Max sample rate is 192 KHz and data precision is 24-bit | |
| Real-time Adaptive ANC | ||
| Call AI Noise suppression and echo cancellation |
The Airoha chip on paper is the better chip, as it is on an improved smaller node, and uses the newer Cortex-M33 cores. Both of these should help reduce power consumption, resulting in an improvement in the battery life. Whether this alone is enough to provide the significant increases in battery life, I do not know, but it could be.
I think that covers most of the details from the FCC photos. I am hoping for a more in depth teardown from 52Audio, but the new headsets have not been announced in China yet.
I am still using the WH-CH730N on a daily basis, testing it, and further comparing it to the WH-CH720N. If you have any questions regarding the new WH-CH730N, please post them in the comments on the review.
