Using a modified 1272 as a mic preamp is an excellent application. In this setup, you can drive its input for color (often with a stepped attenuator for gain staging) and use a second knob on the output to attenuate the signal before it hits your converters. This allows you to saturate the 1272's front end for harmonic distortion without overloading your audio interface.
To achieve more than 40dB of gain safely, you must add a secondary gain stage. Builders do this by: Neve 1272 Schematic
Are you using components or modern Carnhill reproductions? Using a modified 1272 as a mic preamp
According to historical documentation from DIY Recording Equipment , the Neve 1272 module was used for "line makeup gain" or bus amplification. It was never originally intended to be a microphone preamplifier with a stepped gain switch. To achieve more than 40dB of gain safely,