A general rule of thumb is that the load resistance is at 10 times or higher than the coil impedance.
My suggestion is buy a metal film resistor kit, starting with 82Ω, and try different values to find what works best for you.
moving coil loading
I'm getting back into my audiophile hobby and dusting off my vintage gear. I have a question on the preamp loading impedance my Fidelity Research MC201 cartridge. The specs for the cartridge are:
Stylus: 0.3 x 2mil linecontact solid diamond stylus
Output voltage: 0.16mV
Coil impedance: 8 ohms
Load impedance: 10 ohms
My Acoustat Trans nova preamp allows me to install any resisters required for loading the MC circuit. Just not sure on what value resistors to use. Any guidance would be appreciated. If more information is needed let me know
A general rule of thumb is that the load resistance is at 10 times or higher than the coil impedance. My suggestion is buy a metal film resistor kit, starting with 82Ω, and try different values to find what works best for you.

must be an error, load impedance guidance: probably 100 ohms, not 10. gain and load are inverse. high gain/low load. low gain/high load yours is a difficult combination of very low signal strength and 8 ohm resistance. an X Factor of 25 would boost 0.16mv to 4.0mv, I like that. X factor 25 squared = 625. 47000 / 625 = 75 ohm load, a bit low .... X factor 20 boost’s 0.16mv to 3.2mv weaker than I would want. x factor 20 squared = 400. 47000 / 400 = 118 ohm load, good. don’t forget, there is a slight loss of signal strength, i.e. calculated 4.0mv might actually be 3.8mv; 3.2mv might actually be 3.0mv, just guessing here. ......................... solution: for cartridges with these difficult relationships: a phono stage with separate gain choices and separate load choices. opens up the choices to nearly anything. they get expensive. Or, change to a cartridge with more compatible relationship, in your case, lower impedance, or higher output.

I went from knowing nothing to learning here, then researching ... for myself and friends. I made a virtual system with copies of SUT pages I have gathered you will need to increase your screen’s zoom to read some charts .................................. SUT indications can be quite confusing, i.e. my Fidelity Research FRT4, in round numbers: setting 3 ohms is x Factor 36. (+31 db) setting 10 ohms is x factor 21 (+26db) (possibly what your #10 is referring to?) setting 30 ohms is x factor 18 (+25db) setting 100 ohms is x factor 11 (+20db) ........................................ a borderline low signal strength needs to be checked against your preamp’s mm phono sensitivity, i.e. my mx110z preamp's phono sensitivity is 3.0 mv. thus the calculated 3.2mv above would not be my choice. 
@vtacoustatx You are not loading the cartridge to any effect you can hear until the load is extremely low. The loading resistor is there for the benefit of the phono preamp, which apparently is sensitive to Radio Frequency Interference (RFI). The cartridge is an inductor and the tonearm cable has capacitance so they have a resonant frequency which is often 1MHz or higher. When energized, this resonance is essentially RFI that can mess with the input of many phono sections; hence the resistor, which detunes the resonance. So ignore the stuff you commonly see about '10x the impedance of the cartridge'. All that's important for your phono section is the elimination of RFI. So the highest resistor value that does that is the right value. BTW, when you load the cartridge you make the cantilever stiffer since you are asking more work of the cartridge. The industry standard for cartridge loading is 47,000 Ohm (47K); when you make it drive 400 Ohms you are asking two orders magnitude more work and that has to come from somewhere. That additional stiffness is decreased compliance so the cartridge may not track as expected in the arm. It also reduces the ability of the cartridge to trace higher frequencies (both measurable and audible) which means there is a risk of the loading resistor becoming a tone control. If the phono section is resistant to RFI at its input, its plug and play with no worries about loading (this isn't true for MM high output cartridges; that's an entirely different topic).
