Purchased on Amazon. This is the main unit only. I haven't used it much because I bought a higher-end model. There are no operational problems. I think there are no noticeable scratches. It can be connected with 6.35mm and 4.4mm. 【Brand and Model】 The SMSL DS100 is a USB DAC that supports high-resolution audio. It is ideal for audio enthusiasts seeking high-quality music playback. 【Connectivity】 It has USB, optical, and coaxial input terminals, allowing connection to various devices. The output terminals are left and right analog outputs, allowing easy connection to speakers and headphones. 【Design】 The simple and stylish black casing will match any audio system. It's easy to operate, with a knob for easy volume adjustment. - Brand: SMSL - Model: DS100 - Color: Black - Input Terminals: USB, Optical, Coaxial - Output Terminals: R, L - Features: High-resolution audio support