The xDuoo MT-603 brings a soft, smooth tube touch to your music. It features a high-quality 12AU7 tube to add a touch of sweetness to our music, making it more musical and enjoyable. xDuoo MT-603 can be connected to up to four devices at once. It features three RCA aux input ports on the back and a 3.5mm aux input at the front of the device. The active input can be easily switched using high-quality Toneluck switches on the front. xDuoo MT-603 has a premium, sturdy build with sandblasted texture panel and a solid aluminum alloy chassis. It effectively prevents external signal interference providing the users with a clean output signal. xDuoo has featured premium Toneluck push button switches on the MT-603. Toneluck is a well-known brand that manufactures switches and OEM parts for many world-famous brands in different categories. They are durable and have a rich feel to them.