Dave reverse engineers the XuanZu X2U808 HiFi 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 HowTo video:    • EEVblog #675  How To Reverse Enginee...  
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