The new generation of aune's fully discrete Class-A headphone amplifiers with Twin JFET, R2R volume control, 2 selectable current levels (A-L/A-H Class-A quiescent current per transistor), up to 7.5 W output power, 3 groups of headphone outputs + 2 groups of preamplifier outputs, etc. It is a powerful headphone amplifier with the best sound and high performance. The power amplifier of the S17 Pro EVO works with two pairs of output transistors connected in parallel. The amplifier has a total of 16 output transistors. The maximum output power is 7.5 W. Each channel of the S17 Pro EVO has two pairs of transistors connected in parallel, so that the quiescent current per channel can be up to 100mA/200mA. The S17 Pro Evo utilises JRC's R2R electronic volume chip and associated operational amplifiers to create the 4-way balanced R2R volume control. The S17 Pro EVO has two gain settings, each with a different output level. The low gain utilises the Class A amplifier's ability to keep the transistors in linear operation to drive IEMs well and properly, while the high gain is up to 7.5W and can drive high power headphones well.