Thank Nkj. I just opened the receptacle and checked ground with the ratshack tester - and it is just as you describe - grounded when the receptacle is screwed into the conduit box, not when unplugged.
I was going to run a wire from the ground screw to the box as you also suggest, but my multimeter shows continiuty from the ground screw to the receptacle ends, which are firmly screwed to the conduit box anyway, so I don't see the point of a separate wire. Effectively, screwing the receptacle to the box grounds the box, as the ratshack tester shows.
Unfortunately I don't have the skills to check to see whether the conduit is firmly grounded to the circuit breaker box at the other end. It sound like I need to bring an electrician here, and in fact I have been considering a dedicated line for some time.
For now I'm going to replace the receptacle as it was (unless you really tell me a wire from the ground screw on the receptacle to a screw on the conduit box is somehow different from the (ground-continuous) receptacle-ends being firmly screwed onto the box).
Next I'm going to try swapping the Io's power umbilicals, and then the EL-34s, to see if that makes any difference.
I take your point about running the Io all-out in NYC. I probably could use the 72 db setting as well. But the 80 db setting sounds so good in my current system that I'm reluctant to switch.
I haven't been able to get in touch with Jim White yet - he's a hard man to get hold of!
Patrick
I was going to run a wire from the ground screw to the box as you also suggest, but my multimeter shows continiuty from the ground screw to the receptacle ends, which are firmly screwed to the conduit box anyway, so I don't see the point of a separate wire. Effectively, screwing the receptacle to the box grounds the box, as the ratshack tester shows.
Unfortunately I don't have the skills to check to see whether the conduit is firmly grounded to the circuit breaker box at the other end. It sound like I need to bring an electrician here, and in fact I have been considering a dedicated line for some time.
For now I'm going to replace the receptacle as it was (unless you really tell me a wire from the ground screw on the receptacle to a screw on the conduit box is somehow different from the (ground-continuous) receptacle-ends being firmly screwed onto the box).
Next I'm going to try swapping the Io's power umbilicals, and then the EL-34s, to see if that makes any difference.
I take your point about running the Io all-out in NYC. I probably could use the 72 db setting as well. But the 80 db setting sounds so good in my current system that I'm reluctant to switch.
I haven't been able to get in touch with Jim White yet - he's a hard man to get hold of!
Patrick