the last 4 tube amps I've built were constructed on PCbs I etched myself. I used a ground plane in all of them and every one of them is silent, no hum. I have tried various impedance phones with each ranging from 64 Ohms to 300 Ohms and the result is the same. I did some homework on board layout and did my best to keep DC power away from signal traces and so on... My question is "does a single wire from a ground plane to power ground on a panel jack constitute a star ground"? I am far from what I would call an expert on laying out PCBs, I just try to use the largest feasible traces on the amp boards, keep the signals away from power and not use a ground plane for the PSUs Ive built.
All of the amps so far have been low voltage hybrids except for the 6DJ8 amp which was almost 300 volts DC on the PSU, split into 150 volts for B+
Am I just lucky or is the PCB layout and the use of a ground plane not that critical for eliminating hum?