Modern smart TVs Xiaomi Mi TV and Redmi TV offer impressive image quality, but built-in acoustic systems often leave much to be desired, especially for connoisseurs of surround sound. To connect an external audio system, soundbar or home theater owners often face the need to use digital optical output. This is where the S/PDIF interface comes to the scene, which provides uncompressed or compressed multichannel audio without loss of quality.
Many users mistakenly believe that it is enough to simply connect devices with a cable, but there are important software nuances in the Android TV ecosystem on which Xiaomi TVs are based. A key feature is that the physical Mini-Jack 3.5 mm connector on the back of Xiaomi TVs often performs a dual function: it serves both analog output and digital S/PDIF. This means that activating the digital stream requires not only the right cable, but also competent configuration of the software part of the operating system.
In this guide, we will take a closer look at the connection process, selecting the right adapters, and fine-tuning audio settings to maximize playback, and learn how to get around the limitations of embedded speakers and unlock the potential of your audio system, whether it’s an expensive Dolby Digital-enabled receiver or a compact soundbar.
What is S/PDIF and why is it needed in Xiaomi TVs?
S/PDIF (Sony/Philips Digital Interface) is a digital audio transmission standard designed to connect household audio equipment. Unlike analog interfaces that transmit an electrical signal that depends on the quality of the cable and interference, the digital interface transmits data in zeros and ones, which ensures that the sound coming out of a Xiaomi TV is identical to the sound coming to the decoder of your audio system, without distortion and noise.
In Xiaomi Mi TV Stick, Mi Box and modern Mi TV 4A/4S/5 series panels, this interface is often implemented via a combined connector.This allows manufacturers to make devices thinner, sacrificing the number of individual ports. The main advantage of using optical output over Bluetooth is the stability of the connection and support for multi-channel formats, which Bluetooth often cannot transmit in its original quality.
The use of digital output is especially relevant if you are watching content in high resolution or playing games with surround sound support. Analog output, even high-quality, is not able to transmit encoded streams of DTS or Dolby Digital Plus in its original form, requiring transcoding, which leads to the loss of details of the sound picture.
Physical Connection: Cables and Adapters
The first step is to get the devices connected physically properly. Because Xiaomi TVs most often use a 3.5mm connector to output a digital signal, you'll need a special adapter cable. A standard jack-jack audio cable won't work here, because it's designed for analog signal. You need a 3.5mm to Optical Toslink cable.
When buying a cable, pay attention to the label: there should be a 3.5mm plug on one end and a square-shaped optical connector with a protective plug on the other. It is important to understand that not all 3.5mm cables are the same: some are for analogue sound only (AUX), others are for digital. For Xiaomi TVs, it is critical to use a Toslink-enabled cable.
⚠️ Note: Do not try to use the usual AUX-And the signal just won't pass, because the conventional cable transmits electric current, and the fiber optic cable transmits light flux.
The connection process is as follows:
- 🔌 Insert the plug 3.5 mm in the port AV IN / Audio Out on the back of Xiaomi TV.
- 🔦 Remove the protective plugs from the optical cable (if any) and connect it to the adapter.
- 📺 The second end of the optical cable (Toslink) connect to the Optical In port on your soundbar or receiver.
- 💡 Make sure the cable is not clamped and has no sharp breaks, as there is a fragile fiberglass inside.
Configuring sound parameters in the Android TV system
Android TV
Xiaomi
You need to find the audio output item. The path may vary slightly depending on the firmware version, but it usually looks like this: Settings → Device → Sound → Digital Output. In this menu, you will be asked to choose the output format. For maximum quality, choose the Pass-through option or Dolby Digital option.
If you choose PCM mode, the TV will decode the sound and transmit it in stereo format, which will deprive you of the ability to use the decoders of your external device for formats like DTS or Dolby Atmos. Pass-through mode transmits raw bitstream directly to the external system, which is engaged in decoding.
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If you have lost the sound after selecting the Dolby Digital format, check if your audio system supports the codec, otherwise return the settings to PCM or Stereo mode.
Solving problems with coding formats and codecs
Xiaomi
Netflix
YouTube
Mi TV
Dolby Digital Plus
In such cases, the TV can automatically switch to the PCM stereo, or you can hear the characteristic digital noise instead of sound. To solve this problem, you can use third-party players such as VLC for Android or Kodi, which have their own audio output settings and can force the stream to be recoded into a compatible format on the fly.
The S/PDIF interface has a bitrate limit, so high-resolution formats such as Dolby TrueHD or DTS-HD Master Audio cannot be transmitted in full through optics, in which case the sound will be downgraded to the core format.
| Sound format | Support through S/PDIF | Quality of transmission | Recommended treatment |
|---|---|---|---|
| PCM Stereo | Complete. | Basic (2.0) | PCM |
| Dolby Digital (AC3) | Complete. | High (5.1) | Pass-through |
| DTS | Depends on the model. | High (5.1) | Pass-through |
| Dolby Digital Plus | Limited. | Medium (compresses) | Auto / PCM |
Using HDMI ARC/eARC as an alternative
While the topic of this article is S/PDIF, one can’t help but mention the more modern method of connectivity, HDMI ARC (Audio Return Channel).If your audio system and Xiaomi TV are equipped with an HDMI port with ARC or eARC support, this will be the preferred option. HDMI allows you to transfer a wider range of formats, including Lossless audio, which does not “get” into the narrow neck of the optical cable.
The advantage of HDMI ARC over S/PDIF is also the ease of control. Using the CEC protocol, you can control the soundbar volume with the remote control, and when you turn on the TV, the sound system will automatically turn on. The optical interface lacks this intelligent connection and requires separate control.
However, S/PDIF remains relevant for connecting old but high-quality hardware that does not have an HDMI input.In addition, the optical connection is completely electroplated, which eliminates the appearance of a 50 Hz network background, which is sometimes found when connecting over HDMI.
⚠️ Note: When switching between HDMI ARC Optical S/PDIF be sure to turn off one of the cables or change the priority output in the audio settings, otherwise there may be a conflict of devices and loss of audio signal.
Why is there no sound in some applications?
Diagnostics and troubleshooting
If you don't have the sound after all the settings, or if it's intermittent, you need to do a diagnostic, and first of all, check if the red light on the end of the optical cable is on when you connect to the TV, and if there's no light, then the digital output is not software activated or the cable is defective.
A common problem is desynchronizing sound and image. This can happen when using heavy codecs. In the settings of the Xiaomi TV, find "Correct Sound Lag" or "Lip Sync" and adjust the value in milliseconds. Also try rebooting both devices along the chain: first turn off the TV and soundbar, disconnect them from the network for 1 minute, then turn on the soundbar, and after 10 seconds, the TV.
In rare cases, the problem lies in the length of the optical cable. A standard Toslink cable should not be longer than 5-10 meters, otherwise the signal will fade. If you need a longer distance, use active optical cables or converters.
- 🔍 Check the attachment density of the plug in the socket 3.5 mm - it should sit very tightly.
- 🔄 Try resetting the TV sound settings to factory via the Settings menu → The device → On TV. → Reset.
- 🔊 Make sure that the external device has the correct source of the signal (Source: Optical/Toslink).
☑️ Checklist for connection check
Conclusion and final recommendations
Connecting an S/PDIF to a Xiaomi TV is a great way to significantly improve the sound quality without buying new technology. Despite using a compromise 3.5mm connector, if properly set up, you can achieve a clean and powerful sound that will turn watching movies into a cinematic event.
The key is to keep the software settings and choose the right adapter cable in mind. Ignoring Pass-through mode will negate all the benefits of digital connectivity, leaving you with standard stereo. Experiment with equalizer and format settings to find the perfect balance for your acoustic system.
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The right setup of the digital output (Pass-through) is more important than the cost of the cable, as it allows the external system to reach its potential.