My personal favorite is the Parasound JC-3 jr (I simply prefer SUT's for LOMC use -so don't use it's MC capabilities) -without sounding soft or rolled off in the HF -John Curl's design simply is the most relaxed -plain pleasant to listen thru. I also own and enjoy: old Bryston BP-1.5 (-mainly used for LOMC Denon carts), Hegel V-10, ELAC PPA-2 and Hagerman Bugle II -these are all -IMHO opinion excellent MM preamps.I also own a Opera Consance MM tube pre-amp ( puzzling design -transformer on this unit's power supply seems way more than required to light up a couple of tubes ?). Lounge Audio LC-1 ( factory modified to have 47 pF input cap for use with AT MM carts) also works a treat with London Decca carts ( and a Lounge audio Copla), Own 2 of the art DJ Pre II ( 1 modified for 100 pF input -again for AT MM carts) and the newer Art Pro -actually like the Pre II better for MM carts-but am impressed with the MC input on the newer model, Ifi iPhono II (owned a one -but sold it off when I got the II). Also owned and used the original model Schiit Mani - never ran a LOMC into it -but neither I or the 2 other friends I loaned it to were impressed with it as a Mm preamp. Sold off -understand Schiit's up to a Mk 3 variant at this time . Parasound XRM -good value for money -but frankly the JC-3 jr just spanked it -sold off.
It's hard to describe what makes the Parasound JC-3 jr the best to my old nun handles? I simply find myself going ahhh -that's just right -within about 2 min . of plugging any of my MM/IM carts into it. The other preamps have their virtues (the ART DJ pre II is just gobsmacking good for -the money) - the other preamps will shine with specific carts hooked into them -but the JC-3 jr is IMHO / limited experience the universal best.