U.S.-based company Avantree Corp. has released its ‘Quartet’ audio solution that enables multiple sets of headphones to be wirelessly connected to a single audio source. The base solution consists of four pairs of headphones and a transmitter base that can wirelessly relay audio to the headphones from any device that can output audio through an AUX or optical jack, such as a television, projector or stereo receiver.
Employing Nordic Semiconductor’s nRF52832 general purpose multiprotocol System-on-Chip (SoC) in both the headphones and the transmitter base to run the proprietary 2.4 GHz protocol for wireless audio transmission, the solution is designed for applications where multiple sets of headphones need to be connected to the same source, for example, in classrooms, aged care facilities, or outdoor cinemas. Latency is as low as 7 ms, eliminating any lip sync problems during TV or movie playback. The nRF52832 SoC’s multiprotocol radio enables Quartet to reliably transmit audio at a range of up to 100 meters outdoors, or 30 meters indoors. It offers a maximum receive (RX) sensitivity of -96-dBm and a maximum transmit (TX) output of +4-dBm, and a total link budget of >100dBm.
The scalable solution enables up to 100 pairs of headphones to be connected to a single transmitter base, with each pair offering independent volume control so people with different levels of hearing can set their own desired volume. A ‘pass-through’ feature also allows existing soundbars or stereo receiver/speaker systems to simultaneously play the audio, for situations where some listeners prefer not to use headphones.
The processor-intensive application is powered by the nRF52832’s 64 MHz, 32-bit Arm® Cortex® M4 processor with floating point unit (FPU), and its generous 512kB Flash memory and 64kB RAM. The nRF Connect SDK [Software Development Kit] for the nRF52832 integrates the Zephyr RTOS, supports applications using Bluetooth LE, Bluetooth mesh and Thread, and includes examples, Bluetooth LE profiles and driver support for all peripherals.
The Quartet headphones are powered by lithium batteries and can last up to 20 hours between charges, thanks in part to the ultra low power characteristics of the nRF52832 SoC, with features such as the 2.4GHz radio’s 5.5mA peak RX/TX currents and a fully-automatic power management system. “Having the longest possible battery life was very important when choosing a wireless chip for Quartet,” says Howard Leung, Chief Product Officer at Avantree. “This was especially true when considering the major usage scenarios, such as customers wanting to watch television for extended periods without charging their headphones.
“The Arm CPU capability, large memory capacity, radio sensitivity, and low power consumption were all key factors in chip selection, but our main design necessity was the low latency and high scalability offered by the nRF52832 SoC.”