I think it is a dangerous game for amateurs like us (me included) to toss around these terms. First of all, "gain" is a term associated with an increase in the voltage component of an audio signal. The decibel (db) is defined by a certain amount of change (up or down) of voltage, not current. For a cartridge, an approximation of its current output can be arrived at by dividing its signal voltage output by its internal resistance, which is just Ohm’s Law. The MSL with a 0.3mV output and its internal R of 0.6 ohms would then have a current output of about 500 microamperes, at the standard stylus velocity. You can use that number to compare it to other LOMC cartridges in terms of how the cartridge might drive a current mode phono stage. (I don’t use the term "transimpedance" as it suggests impedance is not a consideration at all, but I think it IS a consideration.) I have done this for a few cartridges, and the MSL would rank among those that make "a lot" of current. For another example, my Ortofon MC2000 has an output of 0.05mV with an internal Z of 2 ohms. That suggests the current output is 25 microamperes. Then you look at the particular current drive phono stage; they all have a finite input impedance greater than zero, where zero is the theoretical desired impedance for pure current drive. Fact is, the actual input impedance of various current driven phono stages seems to range from 2-3 ohms to as much as 20 ohms, where the data are even available. Most makers hide that information. This finite input impedance causes a very specific interaction of each LOMC with each of the many different current driven phono stages. In the case of the MSL driving the Einstein, I cannot find for sure the input impedance of the Einstein, but there is one spec on their website that suggests it might be 12 ohms. In that case, the MSL is going to be driving the Einstein as if in voltage mode, because the input impedance of the phono stage (12 ohms) is way more than 10X the output impedance of the cartridge (0.6 ohms). I have done such a thing with my MC2000; I have an outboard current drive gain stage (gain only; it does not do RIAA) that has a high-ish input Z similar to the Einstein, and the ratio of its input Z to the output Z of the MC2000 looks more like voltage drive than current drive. It works great in conjunction with connecting it to the MM input of a phono stage. I also use the MC2000 with a BMC MCCI current drive phono (2-3 ohms input Z); that works fine too, once I set the gain in the MCCI to +11db. What’s going on in these current drive phono stages, I think, is the input stage senses current or voltage depending upon impedance matching and immediately converts it to voltage. After the input stage, it’s all in voltage mode, including RIAA correction. At its output, I think the MCCI has an additional voltage mode gain stage that can either be bypassed ("0db" setting) or set to add various amounts of voltage gain (+7db, +11db, or +14db). The net result is I think every combo of LOMC cartridge and current gain phono will have a unique sound.
