The FiiO R9 delivers impressive audio performance thanks to its five-stage audio architecture with carefully designed IV, LPF, gain, preamplification and current expansion stages. A key component of the audio circuitry is the OPA2211 operational amplifiers, which are manufactured in the Silicon Germanium (SiGe) CMOS fabrication process that ensures the chip's outstanding performance. The variable gain and variable supply voltage result in 5 gain levels, allowing you to precisely set the desired volume. Whether you're using IEMs or hard to drive headphones, you'll have a great listening experience. The FiiO R9's internal power supply, digital parts, DAC and headphone amplifier are all located on separate circuit boards. In addition, there are metal shields to completely isolate the DAC and THX headphone amplifier sections. These four main components of the audio circuitry are housed on independent boards to avoid crosstalk, ensuring that the processed audio signals and their output are accurate, clean and maintain their dynamics. FiiO R9 features a new, low-noise, high-efficiency and long-life industrial-grade 40W power supply that supports an extremely wide input voltage range (85~305VAC) and can operate in a wide temperature range (-40℃~85℃) and is designed to last 500,000 hours. The FiiO R9 can also be powered by an external DC power supply*, allowing you to pair the R9 with a powerful linear power supply that provides its own sound. When the R9 is connected to an external power supply, you can also activate the "Ground Lift" function to reduce crosstalk and achieve a cleaner sound. The analogue part of the audio circuit has a finely divided, multi-stage power supply, including digital-to-analogue conversion, LPF, preamp processing, gain drive and other power supply stages. Each power supply stage uses many precision LDOs to stabilise the secondary voltage, ensuring a clean and stable power supply.