Thank you for your comments
Yes, I will improve all that.
I will change the potentiometer cables and put shielded. Then I will test the Smeter with the manager Ubitx.
On the diagram, as M0THY says, we can improve the sound by modifying the cabling of the potentiometer.
See what it says in the pdf. I put you the plan of its construction which I inspired.
This should make the AGC work a little better.
I also made a modification on the mosfet for the famous "pop"
Add diode+ resistor and capacitor
It is true that in this amplification story, we could use a pc amplifier directly as we had on the sound card.
See you soon for news