What do airplane wings, teeter totters, balancing scales, subtraction, gravel sorters, batteries, stereophonic sound, and balanced audio have in common?
They all rely on differences.
- Airplane wings can lift tonnage by the differences in air pressure between the top and bottom surface.
- Put two equal weight people on a teeter totter and nothing happens.
- Place two identical objects on a balance beam scale, even if they are massive, and you get nothing.
- Pea gravel doesn’t come naturally—only rocks having a common size are sorted through an appropriate filter.
- Attach two wires of a lightbulb to the + terminal of a battery, you get nothing—moved to the opposite pole, light.
- We create the phantom third channel of stereophonic sound from elements common to left and right—differences are filtered out of the center.
I am sure there are many more examples of difference amplifiers and common element sorting filters.
You can begin to grasp how a difference amplifier, responsible for eliminating common noise in cables, separates one from the other.