Looking for help with a Benz SL low output cartridge

The Benz SL cartridges have an internal impedance of 12 ohms. It’s kind of on the line for a transimpedance phono stage. No reason not to try it, but only with a return privilege. You cannot use a transimpedance phono with a SUT, so it’s one, or the other. 

I use SUTs with all of my phono stages, but in your situation I would look at upgrading my phono stage, rather than adding a SUT. There is no right or wrong between high gain phono stage, phono stage with SUT, and high gain transimpedance phono, just personal preference. All can yield marvelous results.

Many folks use primary, or secondary, resistive loading on their SUTs to change the impedance. I prefer not to, but it can be necessary in some applications. The Ned Clayton Cinemag 1254 SUT, mentioned earlier, is very reasonably priced and has switches for four different impedances and gains, 1:10, 1:13, 1:20 and 1:40. Kind of the Swiss army knife of modern SUTs.

If you want to play with transimpedance, Hagerman makes an inexpensive transimpedance head amp that could be used in concert with a conventional phono stage like yours.

What line stage are you using and what is the gain?

Whatever you do, don’t mix a current driven phono stage with a SUT.  The two options are mutually exclusive. Also, keep in mind that the markings on a SUT like the one belonging to Elliot are an indication of what the internal resistance of your cartridge should be, in order to match the turns ratio or voltage gain afforded by that particular pair of inputs, as Elliot correctly intimated.  But it’s not absolutely necessary to match the values of the inputs with the value of the internal resistance of your cartridge.  There is some leeway, and you want to choose more for how much gain you really need than for matching the inputs on the SUT to the internal R of the cartridge.  For example, a pair of SUT inputs labeled "3 ohms" will typically afford much more gain than a pair of SUT inputs labeled "10 ohms".  To understand this, you might want to first understand the simple math.  Ideally you want the ratio between the internal resistance of the cartridge to be about 1/10 of the input impedance of the phono stage as seen through the SUT.  The SUT reduces the apparent input Z of the phono by a factor equal to its turns ratio, squared.  So for a 1:10 turns ratio, you divide the input Z of the phono (almost always 47K ohms for an MM phono stage) by 100, which gives 470 ohms. Just apply that conversion and you can see that a 3 ohm cartridge can in theory drive a 30 ohm input Z.  To end up with a 30 ohm input Z, the SUT may have a turns ratio as high as greater than 1:30, which is an amount of gain you will almost never need.  So you are not restricted to using the 3 ohm inputs if you have a 3 ohm cartridge. Etc. The vintage Japanese SUTs are often marked as is Elliot's, and I find it regrettable and confusing for new users.  Bob of Bob's Devices will set you straight.

@dpm2340 rather than spending money on a SUT that will go into KC Vibe, consider upgrading your phono stage. I owned KC Vibe Mk2 and ran Hana EL and Hana ML with it. It’s a good phono stage. But…

Stepping up to 20/20 Mk2 LPS was a very noticeable improvement. McIntosh MP100 is another excellent choice. Whest Two.2 is a considerable improvement over the Vibe as well and so should be the Two.2 Discrete.

Just go up in phono stage quality. You will not regret that decision. 

@dpm2340 I am not aware if you are city-based or rural, as an area where you reside. I'm confident that if you are residing in a populated area, a request made to loan a device for a demo purpose should produce the desired outcome.

What is the unforeseen is how you Wed to a demo device. I have been through numerous SUT's and loaned quite a number as well. To date I maintain two models and have one that is a SUT of interest, as a result of being present when the design was loaned to another system.

I should also state not to overlook a Head Amp. I have loaned in the past few years, a few designs for this device type, all design used produced by the same designer/builder. If they weren't so readily available to be loaned, I would own one.

I'm sure my recently acquired SS phonostage, will end up with a trial using a Head Amp with the MM Input. Why not! 'Pardon the Pun', "nothing ventured, nothing gained".