Fernando, when using a step-up transformer, the output of the transformer is designed to be plugged into the active phono section with a 47k ohm loading(the Levinson phono input should be loaded at 47k ohms).
The actual cartridge loading then is to be set at the transformer inputs, by way of a switch, or plugging in resistors, or whatever method your unit uses for loading.
Loading a cartridge at the transformer requires you to use about 1/2 the normal specified loading impedance, due to the ratio of the transformer windings.
When used with a transformer, the DL103R likes a load between 30 ohms and 40 ohms, but you can try some loadings a bit outside that range if you want, to suit personal taste. I use 40 ohms on my Cotter transformer with a DL103R.
The characteristics of using a transformer as a step-up device define how the input and output loading is done, so you must use a load of 47k ohm on the Levinson phono input, and between 30 ohms and 40 ohms(approximately) on the transformer input loading. If you deviate much from this formula, you will be affecting the sonic performance of the cartridge, and the way it should be loaded for best sound and internal damping characteristics of the cartridge motor.
While I understand Raul's point about transformers, I also have used many myself, and find that good ones can sound excellent as part of the analog chain. If you already have this unit and can put it to good use, it will serve to save you some money and give additional flexibility to which cartridges you can choose for your system.
