@oldears If its not humming I would not worry, but I suspect there is no need for the 'drain' wire, as the preamp is likely electrically grounded via the ground connection of the AC power cord.
We've been making DIN to XLR phono cables for decades; we just tie pin 3 of the DIN (ground of the arm) to the shield which is pin 1 of both XLRs.
We've been making DIN to XLR phono cables for decades; we just tie pin 3 of the DIN (ground of the arm) to the shield which is pin 1 of both XLRs.