Current injection (amplification) phono stages

I think I started a thread on this type of phono stage some time ago, maybe not here.  After reading Fremer's review of the BMC MCCI, I developed a strong curiosity to try it out.  I think Fremer was trying to underplay the fact that he actually found it to outperform his standard piece, in some ways.  Have you heard one?  "Current injection" is a cute term; I hadn't heard that one before.  Aqvox is much liked by its owners, and cost is very reasonable.

I am currently playing with the Avari - it's awesome.  I would like to get the Avari, but am worried about it's resale value - nobody has heard of them, they don't respond to emails, have 0 social media presence, so if I buy it, it will be my "forever" phono.  It is however much better than my phono (built into the Soulution 520 preamp), and it is  better than the 3x as expensive external Soulution phono (5 series)...

The new Sutherland "Phono Loco" is also a transimpedance phono stage that should be on the short list.  It is superior design and offers unbelievable performance - definitely worth checking out.

As I recall, after researching this type of phono stage, I came to the conclusion that there is an internal theoretical contradiction. That is, for ideal transfer of current you would want zero impedance at the input of the phono stage. But in fact you have to have at least some impedance in the form of a resistance between the grid and the ground or cathode of a tube or between the gate and the ground or drain (or collector) of a transistor, or else those devices don’t work. So in operation, they all present at least a two or three ohm parallel resistance at the input. The proof of the pudding would be in the listening.

jwp, Why do you say that the Sutherland is “superior”. What is it superior to, and what makes it superior?

Gold Note PH-10 and i am waiting for external PSU for it 

Don't believe the Goldnote is a current mode stage. 

The ESE Nibiru is another one, perhaps one of the earlier current mode stages. 

Dynavector P75.

@hdm Don’t believe the Goldnote is a current mode stage.

Forgive my english, just missed "current injection" in the topic.
Well, i believe that my WLM Phonata Reference is current mode phono stage for LOMC (automatic load inpedance for any MC).

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.