Zener Bias "Trick" for Cathode Biased Amps

[jbrrrrr]

Hello, amp tinkerers and tube zealots,

I stumbled across this chunk of a schematic somewhere, but I can't remember the source - it looks like this is a technique used in cathode biased amps with a shared cathode resistor, in order to control the amount of stiffness (or lack thereof) by clamping the cathode voltage at the limit set by the parallel zener(s).  See attachment.

Anyone have any experience using this zener trick as a means to control the 'feel' of a cathode biased output section?  It looks to me like in the 3rd schematic on the right of the 'Zener_bias_trick Squash.gif' file, if you wanted to make it switchable, you could maybe use a DPDT to ground the second series zener with one pole, and parallel in another value for the cathode resistor to make sure the bias sits appropriately in either position using the other pole of the switch.  I could see that being a more impactful modification than just increasing the bypass cap value for a stiffer feel.

Would anyone mind verifying if I'm understanding this correctly?

Regarding any other references to this kind of idea, it looks like tubecad.com might have been an early source for this - Broskie wrote about it here, in the second article on this blog post from 2007.  Paul Ruby is also credited in doing something similar but everything I've read about it seems targeted towards removing "buzz" or crossover distortion, specifically from EL84 tubes.