rectify tube 6z4 change to 6x4

6x4 raytheon

                              6Z4 北京曙光

tube amp. DAC w 6z4....coffee shop

https://kao211.blogspot.com/2012/10/da-build-in-human-vocal-4-times.html

https://kao211.blogspot.com/2023/07/jukeboxss-audio-amplifier-modify-volume.html

before tube Tung-Sol 6x4
replaced rectify tube  by 6x4 raytheon
sound more nature ~ more detail

low noise amp. w 6x4 raytheon inside

https://kao211.blogspot.com/2024/07/diy-another-rare-low-noise-tube-pre_28.html