V1 and V2 are the two inputs, Vout is the output. Simple. And this circuit will give you the expected benefits of a balanced input. But it is not a balanced amplifier topology and this is where we wind up getting confused or, in some cases, misled. The circuit above is a balanced input amplifier with a single ended output. It is what many, many amplification circuits do: add balanced capabilities to a single ended topology. We cannot say this is a balanced audio approach. No, we can only say it has a balanced input. Now let's compare to a true balanced design.
Yes they are very different. The true balanced circuit is discrete where the first example shows a simple op amp. But the designer can use either op amps or discrete to make a true balanced design. Note how the true balanced design has two inputs as well as two outputs and everything remains in two's? We'll look more at this topology tomorrow.
0 comments