My interview with our own Nelson Pass appeared in MultimediaManufacturer.
Read it here: http://www.audioamateurinc.com/digital/m3/issue/110/

jan didden

Why would one use balanced interconnects, and how can we make them work well?

Balanced lines came about at a time where very long signal lines were coming in use for telephone and later for large audio performance venues. If you use a single screened line for your signal, and the line is long, the ground current through the screen causes a voltage between the ground points of the cable ends. Since the signal send out (and received) is the difference between the voltage on the signal wire and the ground wire, the unwanted signal (noise, hum) is effectively added to the wanted (music) signal. We don’t want that.

The trick is to use TWO signal lines in parallel. You send the signal over the two lines in such a way that the signal you want to transmit is the difference between the signals on these two wires, and then at the receiving end you have an amp that reacts to the difference between the two lines, so your signal at the far end is the difference between...

There are lots of types of voltage regulators, but in this installment I’ll talk about series regulators.

What’s a regulator? It’s all in the name: it REGULATES the voltage to the circuit to be powered to keep it constant and as free of noise and ripple as practical. The ‘regulation’ means that there is some circuitry that compares a reference voltage, like from a zener diode, to the regulated output voltage, and then uses the difference between the two to adjust another element to null that difference. The ‘compare-and-correct’ is crucial for a regulator, and is done by negative feedback….

Look at Fig 1: is there a regulator in there? No, they are all circuits that try to give a constant, ripple free voltage, but if you start to draw varying currents from them, the output will vary with that current and there is no mechanism that somehow tries to null out that variation. Fig 1c is better than 1b, because Q1 buffers the voltage from the zener reference, so...