Have you tried either the 14dB or the 26dB windings and compared them with the 20 dB?

Transformers often do work better the less transforming they are doing.

It might be interesting to listen to the 14 dB winding loaded by about 1K3 or alternatively the 26dB winding loaded by 36K to see what the effect is. The cartridge will still be seeing about 50 ohms.

Of course I might be missing some key point here but I'd try it!

Edit

The feasibility of this depends on the o/p level available from the EMT aswell.