Where to insert the step up transformer

Dear Cucurello, if the MC output is very low and the phonoamp is far away, do amplify the signal as early as possible and use a low capacitance phono cable. To keep solder joints and connectors to the minimum possible, I would however - whenever possible - integrate the transformer into the phono-input section (especially so as most step-up transformers do furthermore benefit from the additional shielding of the preamps cabinet and the input of the phono/RIAA-preamp can easily adjusted (with tubes.... sometimes with JFets too) to perfectly match teh secondary of the transformer.
Cheers,
D.

Dear Cucurello, you will need shielded cables and transformer cabinet shielded too. If you use bare transfoemers and customize them into a cabinet, make sure all leads - input and output - are twisted tightly. Do connect the cabinet and the transformers ground with a ground connector similar to the ground at the phono preamps input. The signal is nowhere as small as here and the interference from outside sources (radio, cellular, wireless LAN etc.) can be very annoying...... and once picked-up you won't get rid of it.
Cheers,
D.