Master Volume on only one Phase Inverter output

[scstill]

So I was looking at a previous design that I thought was successful,
sounded decent and even better through an external speaker cabinet.
https://stillampd.com/black-and-blues-05

But today it occurred to me that the post PI MV is incorrect as it is only on one output leg.
Why would this approach sound good? What electrical issues does it create?
Thinking I should add a dual pot to include MV on both PI outputs.
Pic shows the single pot and potential for the dual pot.
What do you think?

[SEL49]

That amp has a paraphase PI. The MV pot directly controls the signal level being fed into the top power tube. But look closely. It also controls the signal level being sent to the grid of the 6SC7B half of the PI. This in turns controls the signal level being sent to the lower power tube. So, you kill two birds with a single stone.

[Merlin]

It's never occured to me before, but that's one of the few (maybe the only) advantage of that inverter, thanks!

[scstill]

Thank you.
I suppose at some point I was schooled in this approach or found a similar design that worked.
Its not in my notebook.
It sounds good and has been completed for several years.

I prefer the sound of pentode preamp to the triode.
I like the fact that I can patch both channels
and that I can switch out the internal speaker for an external cabinet.

It has a little more hum than I think it should so maybe I will investigate reducing that.

[pdf64]

I suspect that the negative feedback is insufficient to have any effect?
But the NFB ratio will be affected by the master volume control setting, with the most negative feedback when set electronally halfway.
It seems a better idea to connect the negative feedback to the other 6V6 grid.

[Merlin]

It seems a better idea to connect the negative feedback to the other 6V6 grid.

Only half the output stage would get feedback then

[passaloutre]

Why not send the NFB to the (first) cathode of the phase inverter?