Anyone with Rhea and Shelter 501MkII?

According to the info at the cartridge database, the loading should be 100 ohms or greater. I suggest trying the settings on the Rhea, I can't remember what the built-in loads are, around this value. Listen for the changes in HF and LF and pick one that sounds best to you. That is the way it is done. IME, the Rhea sounded best with the lowest gain setting you can live with to keep the noise floor down. IMO it is much better to turn the volume up a little more than boost the gain. But you can experiment with that and decide what you like best.

Thanks.

I have a Rhea and you can load at 75 or 125 ohms but not 100. Close enough.

My experience is not inconsistent with that of Dan_ed but I would suggest the quality of the tubes in your Rhea will be a factor. After spending considerable time finding quiet tubes, I now prefer to run my Rhea at the highest possible gain setting rather than boost the volume. I believe this is consistent with the Aesthetix viewpoint too.

I remember contacting the distributor when I bought mine two years ago. He had both a load and gain recommendation for my cartridge. I think it was someone at Musical Surroundings but I may be mistaken.

Aesthetix recommended a low output cartridges to me (which I assume means higher gain at the phono stage), so that seems right.

LOADING

Your cartridge calls for "20 ohms with step-up transformer", "100 ohms with head amplifier" (yes! that is confusing).

Because your Rhea doesn't use transformers, I'd say your goal is 100 ohms.

Therefore, Set your Rhea at 75 ohms or 125 ohms (the closest you can get to 100). Whichever sounds better.

GAIN

Your cartridge has output voltage of 0.5mV.

This calls for a gain of 56dB. Your Rhea hits this on the nose.