# What is impedance?

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I’m currently trying to get the hang of electronics and sound production and I come acrosse “impedance issues” from time to time… For instance, “a preamplifier might load the microphone with low impedance, forcing the microphone to work harder and so change its tone quality” or a contact mike having a low amount of bass because its impedance doesn’t suit the amplifier…

Can anyone help me?

In: Physics

Electricity for audio signals is a tradeoff, you want the desired sound with good clarity while minimizing noise. High impedance is one solution to this, where higher voltages and larger currents are used. This tends to overpower electrical noises, but it requires more power. That’s particularly a problem with microphones. Until very recently, batteries sufficient to generate good signals for adequate times were heavy. That’s why you often see tiny microphones tethered to a battery pack clipped to the person’s belt.

Low impedance is a different solution, very small signals, very low resistances, and not batteries. The energy in the sound waves makes the electrical signals, what’s called a sound powered solution. This takes excellent connections, frequent cleaning, and every wire much be shielded to protect from induced currents.

Both solutions can work well, but they don’t mix and match. Or, more realistically, they only mix and match if you have even more expensive gear that can operate in both modes.

This is an electrical engineering term. Impedance is the amount the circuit will fight the current flow running through it.

There are basically 3 main components we use when designing circuits: resistors, inductors, and capacitors. Any combination of these in a circuit cause a certain total impedance, or amount of “friction” the current flow will see.

In your case the microphone has some small electric current carrying the signal of your voice, so impedance will cause higher “friction” of that voice signal.

It essentially means “resistance,” in the electrical engineering sense ot the word. It has to do with how electricity flows through the circuit. They’re designed to have a certain amount of resistance to make the circuits work correctly. I don’t understand the text you quoted entirely but it seems like the preamplifier might have a different design resistance than the other parts and therefore mess with the circuitry?

To impede something is to get in its way or delay it.

Sound and electrical current both resonate or travel in waves. i.e. they have a frequency. When you try to push sound or current through at a similar frequency, it’s easy because there’s nothing pushing back. If you try to push something through at a different frequency, you get impedence – the sound or electricity is trying to move one way, you’re trying to push something the other way.

Imagine pushing a child on a swing – it’s a lot easier if you push at the same frequency as they are swinging. If you try to push forward as they are swinging backwards, a lot less of your energy ends up moving them forwards.

Impedance is simply resistance in an AC circuit.

In a DC circuit, resistance is cut and dry. You put in a 1000 ohm resister and it’s 1000 ohms.

In the AC stuff you’re looking at, it’s not as clear. Inductors (coils, mics, speakers, chokes) generate a magnetic field that resists different frequencies. Capacitors likewise store power and resist changes to current but generally at higher frequencies.

Impedance mismatch means the circuit is expecting a component that resists so many ohms and you’ve used something too big or too small. This means you’re going to end up with a voltage too high and current too low for the circuit or the opposite of a voltage too low and current too high.