Hi Oli
I had more in mind the OP's original request for ideas when I posted rather than the technical aspects of passive preamps which this thread has evolved to.
But yes it would be good to read about measured distortion amounts (generally and not only for LDRs), but I also wonder even if some distortion is measured it will be meaningful in an actual listening environment.
I believe it was my LDR pre that Alan brought round to your gaff. Or maybe the smaller one he put together?
atb
Edward
Current: [P20] Roon/Tidal > Custom PC> Chevron Paradox NDF16 > Phast Pre > Neuro. 686 > Tannoy Berkley (RFC tweaks)