Current injection (amplification) phono stages

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.

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.

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?

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.