I also went thru this recently, started a thread, found a few options, members added a lot to the discussion and suggested choices
https://forum.audiogon.com/discussions/phono-eq-small-inexpensive-two-phono-inputs
For MM, any simple RCA a/b switch will do it, I had an old small Sony Video Switcher, a,b,c,d in, 1 out. Best arm/cartridge direct to phono 1, a/b switch to phono 2 for the other 2 arms.
Then I decided to enter the world of Moving Coil
Any Step Up Transformer (SUT) with a combination of 2 selectible inputs, and PASS will do it, that lets you keep using your existing preamp’s phono, 1 direct, 2 thru SUT.
I got this, 3 selectable inputs. I love it, versatile options for MC, and PASS for MM, separate selector for the 3 rear inputs. You could run all 3 arms thru this, then into your Phono 1 input, use any combo of MM/MC,
https://www.ebay.com/itm/Fidelity-research-FR-FRT-4-Toroidal-Transformer-In-Excellent-Condition/333648114135?ssPageName=STRK%3AMEBIDX%3AIT&_trksid=p2057872.m2749.l2649
https://forum.audiogon.com/discussions/phono-eq-small-inexpensive-two-phono-inputs
For MM, any simple RCA a/b switch will do it, I had an old small Sony Video Switcher, a,b,c,d in, 1 out. Best arm/cartridge direct to phono 1, a/b switch to phono 2 for the other 2 arms.
Then I decided to enter the world of Moving Coil
Any Step Up Transformer (SUT) with a combination of 2 selectible inputs, and PASS will do it, that lets you keep using your existing preamp’s phono, 1 direct, 2 thru SUT.
I got this, 3 selectable inputs. I love it, versatile options for MC, and PASS for MM, separate selector for the 3 rear inputs. You could run all 3 arms thru this, then into your Phono 1 input, use any combo of MM/MC,
https://www.ebay.com/itm/Fidelity-research-FR-FRT-4-Toroidal-Transformer-In-Excellent-Condition/333648114135?ssPageName=STRK%3AMEBIDX%3AIT&_trksid=p2057872.m2749.l2649