The schematic will show an input transformer and an output transformer.
The original 1272 uses a ±24V DC power supply (unregulated or regulated). The 0V rail is usually tied to the chassis ground. Proper grounding is critical to avoid hum. Neve 1272 Schematic
Power and biasing
On the BA284 card, locate the feedback resistor (usually 12k or 15k). Replace it with a resistor. Then, change the input transformer wiring from 1:2 to 1:4. Result: ~55-60dB of microphone gain. This is the classic "Vintage 1272 mod." The schematic will show an input transformer and
Where the secondary of the 10468 input transformer connects. First Stage Gain Tie a resistor here to ground (B-) to boost gain. K Second Stage Gain Neve 1272 Schematic