Audio Transmitter

A Bluetooth audio transmitter is connected to an audio source such as a TV, record player or PC via a cable. Their sound signal is then transmitted by radio and can be played with any Bluetooth headphones or speakers.

A Bluetooth transmitter requires a wired connection to the audio source. The headphone output or stereo cinch output is suitable for this, or the optical digital audio output (SPDIF) on televisions. With an audio extractor, the sound from an HDMI signal can be used. The audio signal is then sent to a Bluetooth headset or speaker using Bluetooth wireless technology. The respective device must first be coupled with the Bluetooth transmitter (pairing). Typically, you press a button on the two devices (transmitter and headphones) to connect them for the first time. After that, it should connect automatically when you turn it on.

A Bluetooth receiver is suitable for this, which is connected to the stereo system with an audio cable. If you then play music on your smartphone or tablet, you will hear the sound through the system. The transmission from the mobile phone runs wirelessly via Bluetooth.

The standard Bluetooth codec ( SBC ) already offers reasonable audio quality with data rates between 192 and 320 kbps. However, the quality at SBC can vary. If the music source is standard music streaming or internet radio, that should be enough for most users. If the two devices involved, ie the Bluetooth transmitter (e.g. mobile phone) and Bluetooth receiver (e.g. headphones), support it, a better codec can be used. This is mainly aptX , of which there are 3 variants: The normal aptX delivers a better and more reliable music quality with 320 kbps. AptX also has lower latency. Latency is the time delay between sending and playback. It doesn't matter with music. But if you want to transfer the sound to a video via Bluetooth, this is very important. Otherwise you hear the door slam in the film after it's already closed. aptX Low Latency was created for such applications. The latency has been reduced here, so that the transmission takes place almost in real time. The delay is under 40ms, which is 4-6 times better than SBC. And aptX HD was developed for music transmission in even better quality. This sends data to compatible devices at a data rate of 576 kbps. This makes sense if the audio signal is uncompressed or streamed "lossless".

Mainly devices from Apple (iPhone, iPad and AirPods) use the AAC codec and then offer a significantly better audio quality than SBC. Third-party devices with AAC often do not use the maximum quality, because a lot of computing power is required for sending. Apple's own services like Apple Music use AAC for transmission, so it doesn't need to be converted by the iPhone. The LDAC codec, which is only used by Sony, has a niche existence. All Bluetooth audio codecs can only transmit a stereo signal, not multi-channel sound. If smartphones or PCs advertise with "Dolby Atmos" via Bluetooth, psychoacoustic calculations are running there. Then a special signal is generated for each ear - but it stays with 2 audio channels.