ZitatAny final schematic about that design?

Best Regards.

Here's what my amp looks like.
I haven't played or heard an original K19 so I can't say how close it is but this circuit works for me.
PA is quite different because of the higher plate resistors of the PI and the 6V6 tubes.
The presence control is borrowed from a Laney Ironheart and allows the negative feedback of the PA to be basically defeated like in the original. Turned to the other side it cuts highs which helps when bright guitars are plugged in. I like some feedback for the clean tones and compensated the lost distortion with the higher plate resistors of the PI.
I tried different phase inverters but this one sounded best to me.
The EF86 channel isn't needed for good clean tone, but I really recommend the tone stack mid scoop switch.

Here's a sloppy sound demo of the K19 channel: https://www.tube-town.de/ttforum/index.php?action=dlattach;topic=24357.0;attach=64395