Magnetic guitar pickups and microphones seem to do the same job: they turn the sounds we’re making into electrical signals, which we then either record, or amplify and use to drive speakers (or both). They’re the first thing in a chain that takes a quiet sound and makes it louder. But can we say  that “a microphone is a pickup” or “a pickup is a microphone?” What are the differences and similarities between these two devices?

Firstly, let’s look at the similarities. As I said above, they both seem to do pretty much the same job – generate electrical energy from another type of energy. They are both transducers.

With guitar pickups, we have a magnet and a coil of wire with a large number of turns. The strings disturb the magnetic field and induce a current in the coil. This is our signal. Certain types of microphones use a similar setup – both dynamic microphones and ribbon microphones rely on sound waves moving a component in the mic, which then disturbs a magnetic field, inducing a current in a nearby coil. There are, however, lots of other kinds of microphones that use different methods to convert sound into electricity.

I don’t think any of these fit into a standard humbucker rout.

Mounting a microphone that pointed at your electric guitar would certainly pick up some sound and allow you to amplify it. In fact this is quite common with acoustic guitars. So we can see some overlap here too. Having said that, mounting a guitar pickup on a mic stand and having your vocalist sing into it would render him silent (some would say mercifully). So perhaps things aren’t as clear cut.

Not without a mic you can’t, Bob.

The key difference here is that while the end result is the same – an electrical signal that represents sound – the two devices are designed to take a different kind of input. A microphone converts sound into an electrical signal. This means that the “input” is sound waves. These are compression waves, usually in the air around us, but they can travel in liquids and solids too, and there are microphones designed to “hear” sound underwater or deep inside the earth. A microphone can pick up anything that we would call “sound”. In a vacuum, sound cannot travel as there is nothing for it to compress.

This rather charming video demonstrates a few different kinds of microphone.

A guitar pickup cannot pick up sound in this way. It is not designed to. The guitar pickup can only pick up the vibrations of the string within the magnetic field. The strange thing about this is that the vibrations do not need any medium to travel through – a guitar pickup would still work in a vacuum. Seems almost like magic!

Scream all you like pal, we can’t hear you.

Sometimes we do get a pickup that is “microphonic” – this means that it is picking up some sound waves in addition to its intended function. This is a problem at high gain settings, as it can cause a horrible, uncontrolled, squealing feedback. At lower gain settings it doesn’t matter – the signal generated from shouting into it is still far to weak for the pickup to be of any use as a microphone.

Piezo pickups, often used in acoustic guitars and less often in electric guitars, actually do pick up vibrations rather than electromagnetic disturbances. Those are much closer to a microphone in their operation and they will pick up things like taps on the body that a normal pickup won’t.

The real answer to the question comes down to a matter of semantics. What do we actually mean when we say the words “pickup” and “microphone”? If “pickup” means “magnetic pickup”, and “microphone” means “acoustic-to-electric transducer” (which it does, according to Wikipedia), then they are two separate things. A microphone is not a pickup, and a pickup is not a microphone. However, they are both transducers.

So uh, which part do I sing into again?

In conclusion, I’d say that unless your aim is to confuse people (hey, it’s fun sometimes, I know), you should be careful about equating pickups and mics. They don’t do the same job, and they don’t work the same way. Their similarities are subjective – we tend to think of them as similar because they’re the first electrical item in their respective chains – but they’re irrelevant in the techie sphere.
Have you ever tried to use a microphone or a pickup for a purpose other than that for which it’s intended? What were the results?