DigiFi May 2016 issue featuring USB DACs Limited Edition Bonus Complete balanced drive headphone amplifier board, in excellent condition - Magazine: DigiFi Special Edition Stereo Sound - Issue: May 2016 - Number: 22 I bought this intending to use it myself and stored it away. I ended up not needing it, so I'm selling it. The bonus board is unopened and unused; I opened it for the first time to take these photos. I've kept it carefully, so I believe it should work fine. However, I don't have the environment to test it, so I'm sorry, but its operation is unknown. Thank you for looking.