Because the 1272 was originally a , using the schematic to build a summing mixer is a return to its roots. When building a summing circuit with a 1272, the principle is to use 10K or 4.7K input resistors. The Rsh (shunt resistor) is calculated so the total parallel combination of all the inputs is roughly 150 ohms . In the schematic, the 1272 replaces the traditional tube line amplifier and TLA. All you need to do is tweak the gain of the 1272 to about 36dB and it will function beautifully as an active summer.
The Anatomy of Tone: Understanding the Neve 1272 Schematic and Circuit Neve 1272 Schematic
Input stage
, which is an integral part of the second amplification stage. The 1272 vs. 1073 Debate Because the 1272 was originally a , using
This is the heart of the Neve sound. It is a printed circuit board (PCB) containing two separate stages: a preamplifier stage (BA283AM) and a single-ended Class-A output transistor stage (BA283AV). In the schematic, the 1272 replaces the traditional
Follow along with a printed copy of the Neve 1272 schematic:
The rotary switch inserts the second preamp stage into the signal chain (cascading the stages). This provides the massive, high-gain drive characteristic of the 1073. 4. Key Wiring Points on a DIY 1272 Schematic