Good to know!For the DL103 with an output of 0,3mv@5mV/sec, S/N including the Cart becomes an excellent 75.0 dB.
I would just make Rg 20Ω for +36 dB as you did.
You don't ever want to add external resistors to the line receiver inputs if you expect to maintain CMRR.
The absolute values of the internal resistors also vary by ±20%.
You can use THAT1246 and lose 6 dB.
On the MM preamp I tried that and it doesn't really improve noise.