Active Summing Mixer Schematic. A summing amplifier sums several weighted voltages. It is necessary with a passive mixer to provide makeup gain after the fact.
A typical acn or active summing topology is shown in figure 2. At first glance this circuit looks very much like the passive buss shown in figure 1. These inputs represents 5v to logic 1 and ov to logic 0 if the i p resistors in each branch are selected such that the i p value of each resistor is twice the value of the resistor in earlier input branch then a digital logical voltage at the i p terminal will produce an o p which is a weighted totality of the input voltages applied.
The summing amplifier is a very flexible circuit indeed enabling us to effectively add or sum hence its name together several individual input signals.
Also notice that after the 4 3k resistors on the pan switches they go into 10k resistors on the way into the summing bus. Each signal is summed in a totally linear fashion. Its output voltage uo is given by the formula. Hi looking to build a passive summing mixer that i could use to input some xlrs and pan them left or right then have two outputs stereo.
