EEVblog #837 - Reverse Engineering A Valve Headphone Amplifier

Dave reverse engineers the XuanZu X2-U808 Hi-Fi Headphone Amplifier to see if the valves actually do anything. What is the circuit topology? E180F (6J9) pentode valve datasheet: http://frank.pocnet.net/sheets/009/e/... Doug Ford's Microphone design series:    • Microphone Technology & Design   Reverse Engineering How-To video:    • EEVblog #675 - How To Reverse Engineer A R...   Forum: http://www.eevblog.com/forum/blog/eev... EEVblog Main Web Site: http://www.eevblog.com The 2nd EEVblog Channel:    / eevblog2   Support the EEVblog through Patreon!   / eevblog   EEVblog Amazon Store (Dave gets a cut): http://astore.amazon.com/eevblogstore-20 T-Shirts: http://teespring.com/stores/eevblog Donations: http://www.eevblog.com/donations/ Projects: http://www.eevblog.com/projects/ Electronics Info Wiki: http://www.eevblog.com/wiki/ 💗 Likecoin – Coins for Likes: https://likecoin.pro/@eevblog/dil9/hcq3