Digital to analog ground

[GainFreak]

I'm building an amp where a uCU takes care of the switching. I'm deriving 5V for the uCU from preamp tubes' rectified heaters. The things look like on the schematic attached taken from an actual big company amplifier.
Now ideally the digital ground should run through a separate ground wire to the star ground or whatever but I would like to "park" it somewhere where I have a near ground. Some recommend using a ferrite bead and I get that however I don't understand how a capacitor could be used for that (like on the schematic). It will block the DC path and effectively separate the two supplies or I'm missing something?

[g1]

Without a layout, or the actual unit to look at, you can't tell if the 7805 is isolated, or providing ground via heatsink.

[GainFreak]

My 12V regulated heater supply goes to the analog ground. It's powering some relays as well. At some point it goes to a 7805 which provides ground for the uCU. If I connect the uCU ground to the analog one via capacitor practically I don't have ground. That's why I need somebody to explain that schematic to me. I'm currently using a ferrite bead to connect uCUs ground (which I assume is mu digital ground) to the analog one.