Method of electron tube automatic gain control compression not by reducing anode current but by increasing anode potential at same current

Not sure how it works yet but it can be read on previous post.
https://euroelectron.blogspot.com/2019/06/we417a-5842-electron-tube-with-pull-up.html


The power supply to electron tube is a constant current one rather than constant voltage. A more than 10KΩ series power resistor. Then a decoupling 47μF capacitor. This arrangement affects DC quiescent conditions at a time constant dictated by components.


(Not sure yet, it may sound like FM broadcasting. Loudness at peaks remains constant without distortion because of automatic gain reduction. The release time is dictated by above time constant.)


So when a side chain signal is applied or created by the electron tube, instead of anode current decreasing by the change in bias, anode voltage increases by less drop from the power supply.


Electron tube seems not to clip, just possibly gain reduction, ie automatic volume or gain control. Output signal remains maximum without audible distortion.


Is this neat trick taking place also on the Neumann U47 microphone amplifier? See 30KΩ resistor in series with power supply:
http://downloads.bbc.co.uk/rd/pubs/reports/1954-23.pdf


See also:


https://euroelectron.blogspot.com/2019/06/comparing-we417a-open-grid-to-pull-up.html