Amp power supply questions.

[OldSolder]

Thanks for the great ideas gents. I think I will go for the zener diode solution.
And thanks for the maths in coming to the 2k2 resistor value J M Fahey.
Saves me looking up old text books for the formulas.
One more question. As I intend using one vol control, I thought of putting it between the pre and pwr amps.
That way the pre would be running at max "warmth" all the time.
Does that sound like a good idea?
Also my guitar, Gibson Herb Ellis model, doesn't have a tone control on the guitar so I thought of placing a simple guitar type treble roll off
tone control directly after the pre amp input. Sound ok?
Cheers.

[J M Fahey]

Edit: I call "an intelligent voltage divider" a shunt regulator

Me too, but to somebody asking about "voltage dividers" , "intelligent voltage divider" carries the idea straight away .... "shunt regulator" although textbook correct, might not.
Unless the plain "name" is accompanied by an explanation , that is

PD: and I was still too sleepy when I calculated dropping resistor value, see above corrected Math.