Original 1272s didn’t have a gain knob on the front. A modified schematic will incorporate a 12-position rotary switch that adjusts the feedback resistor values on the BA283 card.
The Neve 1272 schematic represents the quintessential Class-A, discrete, transformer-balanced design that defined the "British Sound." Although originally designed as a routing line amplifier, the 1272 has been repurposed by audio engineers for decades as a stellar microphone preamplifier. What is the Neve 1272 Module? Neve 1272 Schematic
At the far right of the schematic, you will find the (typically a Carnhill 10468 or LO1166 ). Original 1272s didn’t have a gain knob on the front
A high-current stage that drives the output transformer. Neve 1272 Schematic