A stock 1272 was never intended to be a mic pre. To convert it, builders typically: Neve 1272 preamp wiring question - Gearspace
. This handles impedance matching and provides the initial voltage step-up. The iconic Go to product viewer dialog for this item. Neve 1272 Schematic
The LO1166 (output) is what provides the "weight" and "glue" to the sound. A stock 1272 was never intended to be a mic pre