Wrapping it up

December 4, 2016 by Paul McGowan

We'll wrap up our series on balanced audio today. I think it's run its course and then some! The last balanced piece I want to touch upon is the phono cartridge. Phono cartridges are all balanced. This is because a phono cartridge is a coil of wire with two ends—naturally balanced audio comes out. Unfortunately it's mostly connected as if it were a single ended device. What a great tragedy! I have never really figured out why phono cartridges and their amplification devices are mostly single ended inputs. We are as guilty as the next manufacturer. Until recently, just about every phono stage we designed connected one side of the balanced output to ground. Our latest, the NPC is a balanced input. But that's rare. So, what have we learned during this series?

There are three main areas of balanced amplifiers and not all are incorporated in products. In fact, most products don't employ all three.
- Balanced input
- Balanced amplifier
- Balanced output
Balanced inputs are common, usually connected to single ended amplifier topologies
Balanced outputs are common, usually tacked on to single ended designs
The big advantage of a balanced input is common mode rejection, where noise signals are squashed
The big advantage of a fully balanced amplifier topology are many, including lower noise and distortion

Tomorrow we'll move on to an interesting new product for vinyl records.