Hi Sondre,
So the pin 7 ground on the tube is just for the internal shield.
When you say “Phono Socket Ground” I assume you’re talking about the RCA in jack? If so, it isn’t connected to the ground of the chassis intentionally so we can isolate the grounds between the pre-amp and the GU50. The ground from the pre-amp will be connected to the RCA shield conductor.
Once the amp is hooked up in circuit, it will have a ground path.
Sorry about the confusion! Technically the driver board is designed to allow a ground wire to be connected at that blue junction (The signal in junction) and it will connect with the rest of the ground path present on the signal board. We design each of the boards this way so we can choose where to take the ground off. However, if we connected the RCA ground to the board, and the board to the chassis star ground, we would then have a ground loop. Where the amplifier has two paths to ground, one through its own IEC socket. And the other through the RCA cable and the pre-amp.
The schematic shows it as being connected to ground because it will be when it’s running. But I’ll have a talk with James about this and see if it’s better to change how we display this on the schematic so it’s less confusing and more accurate to the real world.
Charles