The Phonata operates in current mode with MC cartridges. Not anything really new here. I've been using an Aqvox for about 7 years now which operates similarly.
The loading is not fixed. From the Stereophile review on the Aqvox:
"MC cartridges may produce tiny voltages, but they output decent amounts of current from a source impedance that is both low and resistive. This is ideal for use with a current-mode input because such an input is nearly a short circuit. Different MC cartridges react differently to being plugged into a current-mode input, in part depending, of course, on the internal impedance, but the short-circuit loading means the cartridge is inherently damped and resistive loading becomes a nonissue."
The BMC (like the Aqvox, also designed by Carlos Candeias) is another current mode stage. From the Stereophile review on the BMC:
" Because the input uses current instead of an MC cartridge's ultralow voltage, the input impedance is very low, less than 3 ohms. There is no need, therefore to damp the cartridge's ultrasonic resonance with energy-destroying resistors in parallel with the input."
Some have suggested that current mode phono amplifiers tend to work better with very low impedance MC cartridges and there may be some truth in that.
I've used the Aqvox with a couple of cartridges, most recently a rebuilt Ortofon MC 20 Super with a 5 ohm internal impedance and there does seem to be particular synergy there. Aqvox themselves market a couple of cartridges that appear to be, for all intents and purposes, clones of the MC 20 Super (at least if appearance is any indicator) and do claim great synergy with the current mode input, but I'd expect almost any low impedance MC to work very well.
The loading is not fixed. From the Stereophile review on the Aqvox:
"MC cartridges may produce tiny voltages, but they output decent amounts of current from a source impedance that is both low and resistive. This is ideal for use with a current-mode input because such an input is nearly a short circuit. Different MC cartridges react differently to being plugged into a current-mode input, in part depending, of course, on the internal impedance, but the short-circuit loading means the cartridge is inherently damped and resistive loading becomes a nonissue."
The BMC (like the Aqvox, also designed by Carlos Candeias) is another current mode stage. From the Stereophile review on the BMC:
" Because the input uses current instead of an MC cartridge's ultralow voltage, the input impedance is very low, less than 3 ohms. There is no need, therefore to damp the cartridge's ultrasonic resonance with energy-destroying resistors in parallel with the input."
Some have suggested that current mode phono amplifiers tend to work better with very low impedance MC cartridges and there may be some truth in that.
I've used the Aqvox with a couple of cartridges, most recently a rebuilt Ortofon MC 20 Super with a 5 ohm internal impedance and there does seem to be particular synergy there. Aqvox themselves market a couple of cartridges that appear to be, for all intents and purposes, clones of the MC 20 Super (at least if appearance is any indicator) and do claim great synergy with the current mode input, but I'd expect almost any low impedance MC to work very well.