And steerpike, thanks for the offer to eventually post your paper, you must have felt to be off the hook.
I spent the evening yesterday reading this whole thread again (I printed the thread a few months ago and then filed it, so that was easy), and actually think I know the way forward: have the + and - leads go through the step-ups without any connection to the ground of the arm nor of the turntable, nor to any metallic screening parts of the cartridge (the last should be already allright). All the cable from the cartridge to the preamplifier must have the active + and - leads independent from the ground and from the screening of the cable.
Steerpike_jhb wrote: I've been trying to explain here all along that the reason for using balanced lines is to eliminate noise picked up on the cable. If that isn't the source of the noise, then there is no point in invoking a technology designed to fix it.
Steerpike, I found your earlier comment interesting because it raises the question whether it is actually worth changing the Bent step-up transformers into XLR. Cable length and therefore noise would not be a problem, as my second TT (a splendid Thorens TD 124 with FR-64S and B-60 currently in assembly) will be rather close to the phono preamp. But I think it is still worth doing, because I am currently obliged to use the phono preamp in RCA output mode as the power amps are not balanced. Not yet, because eventually they will be, so the whole chain from the cartridge to the amps will be fully balanced. So better start preparing for the future now.