Thanks, Itsjustme!
To clarify regarding the Herron VTPH-2 specifically, the input stage it provides for LOMC cartridges utilizes a FET (Field Effect Transistor). Consequently, as I mentioned earlier, it has an input impedance that for practical purposes is essentially an infinite number of ohms, but it provides connectors on its rear panel for purposes of connecting loading plugs. 47K loading plugs are supplied as standard with each unit, and Keith Herron can supply plugs in any other values that may be desired. He recommends that with many and perhaps most cartridges the VTPH-2 will provide best results with no loading whatsoever, and I and some other members here have found that to be true with our particular cartridges. Even though, for example, my AT-ART9 has a load resistance recommendation from the manufacturer of "100 ohms minimum."
As you may have seen in the past, Ralph (Atmasphere) has stated in a number of threads here that the need for relatively low impedance loading, where necessary, is mainly due to sensitivity of the particular phono stage to RF frequencies, which can be introduced into it at significant amplitudes as a result of the resonance that is formed at RF frequencies by the interaction of the inductance of LOMC cartridges and the load capacitance that is applied to them. Apparently the VTPH-2 can handle RF frequencies in a more graceful manner than many other phono stages, meaning that such frequencies will have little if any effect on audible frequencies.
So as I had mentioned interposing a SUT between an LOMC cartridge and the LOMC input of the VTPH-2 can be handled in a reasonable manner from the standpoints of cartridge loading and transformer loading. But the concern that would arise in this particular case would be the possibility of a voltage overload in the phono stage and/or in whatever preamp circuitry may be "ahead" of the volume control.
Best regards,
-- Al