I doubt that you can get the original circuit (without the erroneous GND connection) to work with a single supply. The output is biased at 2.5v, and has to swing negative far enough to cut off the JFET, which may require that the output swing below GND. I think changing Vref to 6 volts will solve that problem. The original circuit was apparently meant to run off a 5 volt supply, but it would still require a JFET with a cutoff voltage of less than 1.8 volts. With a 12 volt supply, that shouldn't be a problem.