Q: I recently saw a Tech Tip here on ProSoundWeb about choosing the correct gauge of wire for loudspeakers, which really got me thinking. I’m just starting out in the A/V field and I really want to make sure I’m equipping myself with the best set of knowledge from the get-go.
So my question may be simple (and a little open-ended); however, I could really use an explanation: What is impedance balancing?
A: First of all, what a great sentiment! I’m glad to hear you’re taking such a proactive approach to your professional growth.
One reason you may be a bit confused with the term impedance balancing is that it has been known to go by more than one name. It’s also often called pseudo-balancing, quasi-balancing, resistor balancing, ground compensated balancing, or any of a dozen other similar names.
There are some differences between these, but basically it’s a method of creating an output that will function similar to a balanced output without having to employ all of the electronics normally required in a fully (differentially) balanced system. The benefit is reduced cost and sometimes increased overall flexibility without losing much performance in many situations.
Here’s what it is and how it works: In a truly balanced output there are two conductors and a ground wire. The two conductors each have the output signal on them, but at opposite polarities.
Having this signal on both wires is beneficial for several reasons, but one of the biggest benefits is just in having the two wires, even if signal is only on one of them. A balanced input is able to look at the hot and cold wire’s signal and compare the difference between them.
Any differences get amplified; any signal that’s the same between the two gets canceled. That means noise and hum picked up in the wires along the way will get canceled, and any signal – even if it’s only on one wire – will get amplified. It’s a great system, but comes at a cost in terms of the components required.