Hey Axel,
I still don't get your "voltage mode, vs current mode" statements with respect to transformers. The amount of current a cartridge delivers into the primary of the SUT is fixed by the inductance of the SUT in parallel with the reflected load the transformer provides.
In in your case of the 1:30 and the 47K, the reflected load (~52r) dictates the current through the transformer primary. By adding the 13 ohm resistor in parallel with the primary you do not appreciably adjust the current through the transformer primary. The current output from the cartridge increases but all of the added current simply traverses the resistor to ground.
This doesn't mean that the primary load doesn't have an effect on the transformer behavior since it does. I would expect the output impedance plot of a cartridge to show a rising value with frequency due to the inductance of the coil with a peak at the point where the inductance and capacitance resonate and then a decrease beyond that. This typically happens close to or within the audio band. If you consider how the source impedance has an effect on the transformer behavior and understand that the primary loading resistor damps (and lowers) the output impedance of the cartridge it quickly becomes clear that this is a very complex relationship that doesn't lend itself to generalizations and ROT's
dave
Last part: Therefore "Current mode" means that the cart delivers the most current it can, into the SUT's primary and the best / most when properly impedance matched.
I still don't get your "voltage mode, vs current mode" statements with respect to transformers. The amount of current a cartridge delivers into the primary of the SUT is fixed by the inductance of the SUT in parallel with the reflected load the transformer provides.
In in your case of the 1:30 and the 47K, the reflected load (~52r) dictates the current through the transformer primary. By adding the 13 ohm resistor in parallel with the primary you do not appreciably adjust the current through the transformer primary. The current output from the cartridge increases but all of the added current simply traverses the resistor to ground.
This doesn't mean that the primary load doesn't have an effect on the transformer behavior since it does. I would expect the output impedance plot of a cartridge to show a rising value with frequency due to the inductance of the coil with a peak at the point where the inductance and capacitance resonate and then a decrease beyond that. This typically happens close to or within the audio band. If you consider how the source impedance has an effect on the transformer behavior and understand that the primary loading resistor damps (and lowers) the output impedance of the cartridge it quickly becomes clear that this is a very complex relationship that doesn't lend itself to generalizations and ROT's
dave