Since the BTR15 can work as both a Bluetooth receiver and a USB DAC, FiiO built in a button for PC/BT/PHONE mode. With just one press of a button, you can quickly switch between the three different modes to meet your current scenario for high-quality music enjoyment. The FiiO BTR15 features a global parametric equalizer (PEQ). FiiO's proprietary PEQ algorithm and user interface allow you to select the exact frequencies to adjust in each mode*, along with their gain levels and bandwidth - allowing you to fine-tune the sound exactly how you want it. The upgrades start with the heart of the FiiO BTR15, namely the cores that power it. The BTR15 uses the powerful combination of Qualcomm QCC5125 Bluetooth chip and XMOS 16-core XU316, which supports stable high-res audio playback in any mode* and gives you more ways to immerse yourself in the world of high-quality high-res music. The FiiO BTR15 supports up to 8x MQA decoding, enabling master-level high-resolution sound quality in files of reasonable size suitable for your mobile device. With the BTR15, FiiO is the first to use hot-bent curved glass, which is used on both the front and back of the device. This not only makes the device feel better in the hand, but also gives the BTR15 a more attractive and three-dimensional look. Together with the aluminum alloy middle frame, it makes the BTR15 a pleasant device to use. Like its big brother, the BTR7, the BTR15 also features a large display - a brilliant 0.96-inch OLED display. This display not only allows for more information to be shown at once, but also a larger font - making it easier to see the device status and change various settings. In addition to the standard 3.5mm headphone output, the BTR15 also features the widely used 4.4mm balanced headphone output, which offers greater contact reliability and durability compared to the 2.5mm balanced output. Thanks to the two outputs, you can use the BTR15 with multiple headphones for an even better listening experience.