Owners of Xiaomi Redmi 9T often face a situation where wireless headphones or Bluetooth speakers are not working correctly: the sound is either too quiet even at maximum, or, conversely, deafeningly loud at minimum values of the slider. This problem lies in the volume synchronization function known as absolute volume. In the Android operating system, and especially in the shell of MIUI, this option is created for convenience, but in practice often causes dissynchronization of sound levels between the phone and the connected device.
The essence of the conflict is that the smartphone and headset interpret sound control commands differently. Absolute volume causes the phone to transmit an exact percentage of volume to the headphones, ignoring their own hardware limitations. If the Bluetooth drivers are incompatible, the user gets either a barely audible whisper or a distorted wheezing. On the Redmi 9T model equipped with a Snapdragon 662 processor, this setting can be hidden in the depth of the engineering menu or require activation through special commands.
In this article, we will discuss proven ways to deactivate this feature, learn how to access hidden developer settings and safely change the configuration of the Bluetooth stack, which will give you full control over audio output and eliminate annoying noise surges when listening to music or watching videos.
Understanding the Nature of Volume Conflict in MIUI
The problem with the Xiaomi Redmi 9T's audio desynchronization is due to differences in implementation of the AVRCP (Audio Video Remote Control Profile) protocol. When you plug in a wireless headset, the phone tries to impose its own volume scale on it. However, many headphone manufacturers use their own, independent scale, and as a result, a slider on a smartphone screen can show 50%, while headphones perceive this as 10% or 90% of their maximum.
The MIUI shell is known for aggressively optimizing Bluetooth devices to save battery power, sometimes resulting in incorrect audio flow. Turning off absolute volume allows the two systems to untie, then the phone will control only its output signal, and physical volume will be regulated by buttons on the headphones themselves or the speaker, which is often a more stable solution.
It is worth noting that this feature affects only wireless connections. A wired headset connected via a 3.5 mm or USB-C connector is not affected by these settings, since it uses an analog signal or a digital protocol without the mediation of a complex stack of Bluetooth profiles.
⚠️ Attention: Changing the settings in the developer menu can affect the stability of the Bluetooth connection.If after disabling the function, the headphones stop being determined, just restart the smartphone to reset the protocol settings.
💡
Turning off absolute volume separates the sound control of the phone and headphones, allowing them to be adjusted independently.
Activation of the developer mode on Redmi 9T
Before making changes to Bluetooth, you need to access advanced system settings. In Xiaomi Redmi 9T, the developer’s default menu is hidden from the eyes of the average user to prevent accidental system failure.
The process of turning on is quite simple and doesn't require root rights or a connection to a computer. You need to find a specific string with the build number and quickly click on it several times. The system will count the attempts until the hidden functionality is accessed. This is the standard security procedure for all Android devices.
Once activated successfully, a new item will appear in the main settings menu, and it's inside that that key switches that are responsible for debugging USB, working in the background and, importantly for us, Bluetooth connectivity parameters, without this step, no further action will be possible.
☑️ Activation of the developer mode
Search and disable options through the developer menu
Once the developer mode is activated, we go to directly find the right switch, and the path to that switch may vary slightly depending on the version of MIUI installed on your Redmi 9T, but the logic remains the same. You need to carefully scroll through the list of special features, because there are quite a lot of them.
Find the Bluetooth partition. Some versions of the firmware have the option Disable Absolute Volume, others have the option "Enable Absolute Volume." The switch logic can be inverted: if you tick "Enable," the function works, if you remove it, it shuts down, and our goal is to make the phone stop dictating volume to the external device.
Once you change the position of the slider, make sure you reconnect the headphones. Just turn off and turn on Bluetooth on your smartphone or turn off the headset in the list of devices and reconnect it. Only after you pair it again, the new settings will take effect, and the system will rebuild the audio stream.
What to do if the item is not found?
Use of the ADB Engineering Menu and Commands
If the standard settings of Xiaomi Redmi 9T do not give the desired result or the desired item is missing in your firmware version, you can use more advanced methods. The engineering menu allows you to access the low-level settings of the radio module.
Dial ##6484## or ##3646633##. In the CIT or EngineerMode menu that opens, go to the Hardware Testing tab, then select BT (Bluetooth) and then BT Debug Mode. This may contain additional signal power and profile settings, although the interface is often stripped down in global firmware versions.
A more reliable, but computer-intensive method is to use ADB (Android Debug Bridge), which by connecting the phone to a PC with drivers and platform tools installed, you can type a command that forcibly changes the global settings of the system, which requires debugging over USB on the developer menu.
adb shell settings put global absolute_volume 0This command sets the absolute volume to zero, which effectively turns off synchronization. To return to factory parameters, you can use the value of 1. This method is universal and works even where the graphical interfaces of settings are hidden.
| Method | Difficulty | Essential tools | Efficiency |
|---|---|---|---|
| Developer menu | Low. | Only a smartphone. | Tall. |
| Engineering menu | Medium | Only a smartphone. | Medium |
| ADB teams | Tall. | PC, USB cable, ADB | Maximum |
Additional Bluetooth settings in MIUI
In addition to direct combating absolute volume, there are adjacent settings on the Xiaomi Redmi 9T that can improve sound quality. In the same developer menu, pay attention to the Bluetooth Codec item. By default, the system chooses automatic mode, but sometimes manually selecting an SBC or AAC codec solves problems with quiet sound better than turning off sync.
It's also worth checking the equalizer and sound effects settings in the standard Music app or system audio settings. Some presets, such as Volume Sound or Mi Sound Enhancer, can conflict with the wireless headphone algorithms, creating the illusion of a volume problem. Try turning off all the improvements and check for clean mode.
Another important aspect is the version of the AVRCP protocol. You can find the option “AVRCP Bluetooth Version” on the developer menu. Try switching it from 1.5 or 1.6 to 1.4. Older versions of the protocol often have better compatibility with older or budget headphone models, as they use simpler controls.
💡
After changing the AVRCP version or codec, make sure to “Forget the device” in the Bluetooth settings and pair again, otherwise the settings will not apply.
Diagnosing Sound Problems After Changes
Once you've turned off absolute volume, it's important to get the results right. The first sign of success is two independent scales or a change in the behavior of one common scale. Now, when you reduce the volume on your phone to a minimum, the sound in the headphones may not disappear completely, because they have their "zero" level.
Note the stability of the connection. Volume control decoupling sometimes causes the phone to stop receiving battery status from the headphones or loses connection status information. If you notice that charge is no longer displayed, this is a direct consequence of the changed protocol settings.
In some cases, you may need to choose the optimal balance, for example, leave the absolute volume on, but change the codec to SBC, or vice versa. Each set of equipment (smartphone + headphones) is unique, and the ideal setting is by trial. Redmi 9T has enough flexibility to adjust the settings to find a compromise.
⚠️ Warning: If after all the manipulations, the sound is completely gone, check if the minimum volume is set on the headphones themselves. When the synchronization is turned off, the phone may think that the volume is 100%, and the headphones - that 0%.