Current injection (amplification) phono stages

Chakster , the way these special phono stages work is based on the notion that the first amplification stage becomes part of the cartridge output. So in theory you want the source impedance of the cartridge to be as low as possible. In fact not all low output moving coil cartridges have a source impedance low enough to work really well with this type of phono stage. Ideally you want the source impedance to be below 10 ohms, better yet below five ohms. Thus a cartridge like a denon DL 103 which is low in output but has a source resistance of 33 ohms, would not be a good match for this type of phono stage. (I am not saying it wouldn’t work at all; I am saying it would not give optimal results.) Low output ZYXs with source resistance of 4 ohms work well, on the other hand. HOMCs would not be a good match at all for this reason.

Thanks @lewm 
Now i've checked the article about it from the link above. My "old friend" Dr.Tominari whom i've mentioned in my Dynavector thread invented this method, very interesting:  

Dr. Noburu Tominari of Dynavector was the first to propose using the MC cartridge as a current source and amplify the current from it. This is the current that a cartridge can deliver into a dead short. According to Tominari, all cartridges produce magnetic distortion caused by the nonlinear characteristics within the magnetic materials of the cartridge. These distortions have an adverse effect on the signal produced by the cartridge.  When using current amplification, the magnetic distortion of the cartridge is significantly reduced resulting in better linearity across the whole frequency range."

"Current amplification, also called Current Injection, or CI, is of course the same as a current to voltage (I/V) converter for DACs, except with DACs the source resistances and current levels are higher. Current outputs of moving coil cartridges vary considerably depending on the coil windings of the cartridge. In general, the lower the internal resistance of the cartridge (10 ohms or less), the better the cartridge tolerates the short and produces a usable current output. Many of the higher internal resistance cartridges sound constrained by the shorted output and do not benefit from current injection. However, with the right low internal resistance cartridges, listening to a current injection phono preamp opens the listener to a beautiful new experience of vinyl music without magnetic distortion.

It seems like my WLM Phonata is using same principle, definitely not for all cartridges, but i've got spectacular sound with FR-7F and FR-7Fz LOMC cartridges with WLM current phono stage. My old ART-2000 was also great with that phono stage. Not to mention that my First Watt amp is also current amp (not voltage amp) for cross over less full range speakers.   

The thing is also that none of the current injection phono stages truly present a dead short, either.  They present a very low impedance however (on the order of a few ohms), much lower than that of a conventional phono stage.