The AT-PHA55BT wireless headphone amplifier is a compact but powerful tool that will help you get the most out of your headphones - wherever you go. Utilizing Bluetooth® wireless technology and supporting LDAC, aptX, AAC and SBC audio codecs, the amplifier processes the digital transmission from your Bluetooth device and faithfully converts it to an analog signal via an ESS Technology ES9118 HiFi System-On-Chip (SoC). Offering up to eight hours of continuous use and a max output level of 50 mW + 50 mW, the AT-PHA55BT has the power to drive your headphones to their full potential. Additionally, the amplifier features an output mode switch that allows you to select between two output impedance levels - one suitable for headphones with dynamic drivers, the other for headphones with balanced armature drivers - ensuring you get the best sound possible. The amplifier is designed to suppress wireless jitter and reduce acoustic resonance, and allows for fine audio tuning through its 32-step multilevel digital volume control. The AT-PHA55BT is equipped with LED indicators that display the battery level, pairing and charging status, and the codec currently in use. The amplifier also includes a microphone so you can take calls from a paired smartphone, and comes with a belt clip and a 30 cm (1') USB charging cable.