[Twin JFET | 2 Pairs of Transistors per Channel] JFET has high input impedance and rich sound. The S17 Pro EVO’s Twin JFET is more than that - same temperature rises, same performances and stable mid-point voltage. It’s the ideal input transistor of a headphone amp. | The final output stage uses 2 pairs of output transistors in parallel. The whole device has as many as 16 output transistors. Max output is as high as 7.5 W. It can drive all kinds of headphones and IEMs with ease [Class-A, 2 Levels of Current/Gain] 50 mA/100 mA per transistor; each channel has 2 pairs of transistors in parallel, so the quiescent current of each channel is as high as 100 mA/200 mA. The sound of a class-A amp is mellow, warm and smooth; 2 gain levels: the low gain takes advantage of the class-A amp’s feature that the transistors are always working in the linear area to drive the lEMs well and properly, while the high gain is as high as 7.5 W and thus can drive headphones well with big power [R2R Electronic Volume Chip | Rigorous HiFi Component Selection] Uses the R2R electronic volume chip from JRC and the dedicated op-amps to build the 4-way balanced R2R volume control. High control precision, great channel balance, wide soundstage, accurate positioning. | The components are high-quality and carefully selected, such as the electrolytic capacitors, the ceramic capacitors, the organic thin-film capacitors, the communication-grade PCB, etc. Everything is aimed at good sound [2 Colors to Present Current Level/Temperature | Overheat Protection | 3-Dimensional Cooler Structure] 100 mA mode is a high current Class A operation mode, similar to the GT mode in a racing car. There will be a slow temperature rise. (If the headphone impedance is low, it can lead to a faster temperature rise.) When the device temperature reaches 69 °C, due to overheat protection, the S17 Pro will auto switch to 50 mA Class A current mode which still maintains very good sound quality Powerful and Rich-Sounding | Aesthetic Tuning The S17 Pro uses the 50 W low-ripple toroidal transformer and dual-power design. Digital control and analog are independent from each other, so the analog part can be free from interference. What’s more, it has the 19200 μF capacitor array. They together make the S17 Pro so powerful and rich-sounding. | The tuning is based on real instrument sounds and music pieces referencing, leading to the signature that is natural and full of musicality Please Note - The product must be used at 110V voltage. Excessive voltage will damage the product As aune's new generation of fully-discrete class-A headphone amp, the S17 Pro has the features of twin JFET, R2R volume control, 2 levels of current to select from (50mA/100mA class-A quiescent current per transistor), output power as high as 7.5W, 3 groups of headphone outputs + 2 groups of preamp outputs, etc. It is a high-performance rich-sounding headphone amplifier with high power.