Good eye.Would using a 1246 (+6dB) allow you to drop the resistances even lower...?
I've thought about that and this is one of those cases where it might.
Though it intuitively seems wasteful to throw away gain in a preamp, the NF is about 2 dB better when its running at 56 dB in the INA vs 50 dB in the INA. (Rg is 1R vs 2R2).
So throwing away 6 dB gain in the cross-coupled common mode rejector might measure slightly better.
It's very poor, about 2R. I'm not entirely keen on having it.How linear is hop off resistance of the gain trimpot? Probably OK is you don't measure anything.
The pot is only useable with high output carts requiring relatively low gain. I put it in to cover the >500 uV ones.
Using the pot below 10-20 Ohms isn't practical.
If it were to cover the full range it would be very twitchy.
That's why I have the 56 dB and 46 dB resistors fixed values and in series.