DigiFi No.10 Special Appendix: USB DAC Headphone Amplifier. - I used it once when I purchased it, then wrapped it in a plastic bag and stored it in the original paper box inside a plastic case for a long time. Upon listing, I confirmed its conductivity and was able to use it for PC audio. - The booklet in the photo is an excerpt of the special feature articles related to the USB DAC headphone amplifier (pages 13-29). Not all pages are present, and as the photos show, the booklet itself is not in good condition, so please be aware of this. - As I am an amateur, I do not know the details of sound quality differences due to aging. Please understand this point and consider purchasing. - Please read the above and understand that this is a used item. If you are at all concerned, please refrain from purchasing. Other: - Shipping will be via Rakuraku Mercari or Yuuyu Mercari. - No price reduction. - Listed for collection organization. - No claims, no returns. USB DAC Headphone Amplifier Specifications: ● Input: USB terminal (Type B) ● Output: 3.5Φ stereo mini headphone terminal, RCA pin terminal ● Headphone output: 13mW x 2 (300Ω) ● Line output: RCA 2Vrms (MAX) ● Volume adjustment mechanism: External control of the computer's volume ● Dimensions: W64 x H38 x D94mm Headphone Amplifier