Precision Adder

Precision Adder front view
Precision Adder front view

This is a useful and often needed utility module. The input voltages are precisely added to the outputs.The inputs 1, 3 and 5 are normalized. It can be used in different ways: As three independent adders, as buffered multiple, adding a modulation source simultaneously to all three outputs, adding two, three or four voltages precisely and a few more, depending on your patch. The accuracy depends on the used operational amplifier. For pitch CV I recommend precision OpAmps like the LT1014.

Specs and features

  • 3 independent precision adders
  • Input 1, 3 and five normalized
  • Buffered multiple
  • Additional common modulation inputs
  • Runs on +/-12V and +/-15V
  • Power consumption below 10mA each rail

The documentation and the Gerber files for download can be found in my website.

Precision Adder schematic main PCB
Precision Adder schematic main PCB
Precision Adder schematic control PCB
Precision Adder schematic control PCB

All inputs are buffered with high impedance inputs. They are followed by precision adders where the two inputs and the two additional modulation inputs are added together. The last stage buffers the output and corrects the phase. Inputs 1, 3 and 5 are normalized. The accuracy depends on the used operational amplifier and the matching of the resistors. For pitch CV I recommend precision OpAmps like the LT1014. Match all 10k resistors to 0,1% or better.

Precision Adder side view
Precision Adder side view
Precision Adder populated PCB
Precision Adder populated PCB