I do not think the SUT does anything sonically, just 'magic' passive signal boost. My FRT-4 is totally noiseless, and I use PASS to play MM Cartridges I am very familiar with goint directly to MM Phono Input in the past. If your Phono LOMC input (which is/has a SUT within prior to riaa eq) makes some noise, and your MM Phono has no noise, the FRT-4 will let you send your LOMC to your MM Phono with no added noise.
Changing to the various x-factors/resultant impedances, the volume change is instantly evident, after you adjust the volume, listening for slight variations, they are not immediately obvious.
Changing inputs, listening to different cartridges: Stereo MM/Stereo MC/Mono MM/Mono MC (mine or my friends), you can hear differences, and after you take the time to play a lot of familiar music, you more readily identify your 'preferences' (not better, just preferred).
Both of my cartridges are LOMC with outputs of approximately .25mV.
I’d like to see if adding a SUT in front will lower the noise and sound better than going straight into the MC input. Do you think the FRT-4 inject any sound signature of its own to the signal?
It is my one and only SUT experience, I feel lucky I chose it (based on it's optional features). Absolutely noiselessly pre-pre amp's the delicate phono signal. PASS for MM.
Ideally, separate control of x-factor (signal boost) and loading (impedance) is desired, however I am unwilling to spend the amount of money that requires. The FR-4 has a limited set (4) of inter-related options that work well for me and many MC cartridges, but you need to learn and then do the math when pairing it with a specific MC Cartridge.
Actually, it is:
'TRY' a low signal strength cartridge (Moving Coil), and you
'USE' a SUT to be able to do that. Passive Signal Boost: Magic?
In the beginning, when I was young, ANY and ALL MC Cartridge's made noise! NYET! It was a club for Masochists, Jag V12 Owners, JVC TT-101 and TT-801 Owners
After joining Audiogon in 2019, I decided to finally try a LOMC Cartridge. I got help, followed with research, made some new friends with MC/SUT experiences, decide to go for a long arm at the same time, that led to a larger plinth that led to multiple arms, ......
I am a huge advocate for two tonearms, and a SUT (or phono stage) with multiple and easily selectable inputs is a key ingredient for ease of use.
One day I might change the FRT-4's output cable to one with better connectors, and yet 5 years of happy listening ......
