I've built a headphone amplifier powered by a switch-mode 2-pin wall wart power supply. Internally a virtual ground is created by dividing and buffering the supply voltage. Input and output signals are referenced to virtual ground. I/O connector sleeves are isolated from metal enclosure.
If metal enclosure is not grounded, I obviously get 50Hz background hum, so I tried to connect enclosure to -V, then to virtual ground. In both cases the background hum was gone, but which option is "more proper"?
headphone amp schematic

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    \$\begingroup\$ Since the primary purpose of the chassis shield seems to be signal integrity, I want to say virtual ground. Looking forward to hearing what those with actual knowledge have to say. \$\endgroup\$ – Dampmaskin Sep 23 '19 at 10:12
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    \$\begingroup\$ Which ground can handle an ESD strike best? \$\endgroup\$ – Jeroen3 Sep 23 '19 at 10:44
  • \$\begingroup\$ @Jeroen3 I suppose the -V, supplied by my MeanWell power adapter, is better ESD protected than LM358 with 20Ω output resistor 🤔 \$\endgroup\$ – Volodymyr Smotesko Sep 23 '19 at 11:33
  • \$\begingroup\$ If your chassis is connected by the connector to the sleeve, it'll have to be your virtual ground or you'll be running DC through your headphones. \$\endgroup\$ – Cristobol Polychronopolis Sep 23 '19 at 14:20
  • \$\begingroup\$ @CristobolPolychronopolis I'm using plastic connectors, so sleeves are isolated from the enclosure by default. \$\endgroup\$ – Volodymyr Smotesko Sep 23 '19 at 14:40

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