Distribution Amplifiers and Splitters

When to use a splitter

So, you have a mixer with one output that needs to feed two graphic equalizers and a video capture board. Before you buy a distribution amplifier, check the ouput capabilities of the mixer and the input impedances of the graphic equalizers and video capture board. You can use the following equations to see how much load the different components will put on the mixer output.

For 2 component inputs (2 resistors in parallel):
R_T = total impedance
R₁ = 1st component's input impedance
R₂ = 2nd component's input impedance

RT = R1 * R2 / R1 + R2

For multiple component inputs (multiple resistors in parallel):
R_T = total impedance
R₁ = 1st component's input impedance
R₂ = 2nd component's input impedance
R₃ = 3rd component's input impedance

RT = 1 / ((1 / R1) + (1 / R2) + (1 / R3) + (...))

Example

You have 2 components which have a 25K input impedance and 1 component with a 15K impedance.

Total impedance =
1 / ((1 / 25) + (1 / 25) + (1 / 15)) =
1 / (0.04 + 0.04 + 0.066666) =
1 / 0.1466666 =
6.8K

If your source can't output into 6.8K ohms or less, buy a distribution amplifier. Most quality sources can output into 600 ohms and you only need a splitter. (This is like one of those giant coal trucks pulling a toy wagon. There is no need to buy a new coal truck to pull a few more wagons.)