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On-Camera Audio Recording: Getting Audio Into the Camera

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Question. Will a particular microphone work with a particular camera? In order to use these devices, you have to know how to connect them properly, and in this lesson you'll find out how.

Microphone Inputs

When you're talking about cameras and microphone inputs, the good news is that there aren't a lot of options. You basically only need to keep track of two. Smaller cameras are probably going to have a 3.5mm microphone input, while larger cameras with a bit more real estate to work with are going to have an XLR input. 

XLR Input

An XLR connector is a professional connector. It has three pins in a robust metal housing that can withstand a lot of abuse. We're talking about thousands of connects and disconnects. An XLR is a balanced input, and it can more than likely give you an opportunity to use phantom power, which helps power your microphones. The biggest bonus is that an XLR connector gives you access to the vast majority of microphones out there.

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Professional audio cable. Image source: Envato Elements

3.5mm Input

A 3.5mm input is an unbalanced microphone input that often supplies a very small amount of power for something like a lavaliere microphone. A 3.5mm is not as robust or rugged as an XLR connect, and the preamps found in smaller cameras don't tend to be as high performing as cameras that come with XLR inputs. That doesn't mean you can't get great sound with a small camera and a 3.5mm input—it just means your options are limited.

Balanced vs. Unbalanced

You heard me mention in the comparison, balanced vs. unbalanced. What does that mean?

Unbalanced wiring uses just two connections. You have the signal, and then you have the ground. This is much more susceptible to external noise sources, which limits your ability to use longer cables.

With balanced wiring, you get three connections. You get the signal positive, then you get another copy of the signal that's inverted, which is the signal negative, and you get the ground.

Why is that a big deal? You have a positive signal and a negative signal, and when that balanced signal reaches its destination, the negative side gets flipped so that any noise that was present in the line is now out of phase with itself and cancels itself out. So balanced connections do a much better job of rejecting noise. You can have a cable length of 50ft to even 100ft without any problems, whereas on the unbalanced side, that is a problem.

As I said before, it doesn't mean you can't get great sound if you use a microphone with a 3.5mm connection. It might be noisy, but it probably won't be as long as you keep the cable lengths relatively short.

If you're not going to use an external microphone preamp with a 3.5mm input, it does limit your options to the microphones that work well. You can use a wireless lavaliere that has an unbalanced output. You could use a wired lavaliere as long as the cable length is relatively short, and you can use a small shotgun microphone with a built-in power supply (with a short cable).

The issue with cable length is a little bit of a variable because what might work in one location may not work in another location with more electromagnetic interference. This is the type of thing you run the risk of with unbalanced microphones. You may have a line that's six feet long that works fine 80% of the time, but then you get to a certain location that's wired in such a way that it's outputting some radio frequency, and you'll get noise on the line. That's the benefit of using an XLR system with professional microphones, where that sort of thing almost never happens. 

Preamps and Phantom Power

You can use professional microphones with your camera system that has 3.5mm inputs—you'll just need an external preamp. That's going to be an additional cost, and to get really good preamps, it's going to cost a fair bit of money (US$250–400). You're asking that device to take that balanced signal and give you an unbalanced signal, but you're also asking it to amplify the microphones and to do that without a lot of noise, and that's what can cost money.

You're also going to want phantom power in that device. Phantom power is a bit of extra voltage that's transmitted from the camera—or the preamp, more specifically—to power the electronics in a condenser microphone. You'll learn more about this in a future tutorial, but condenser microphones require power to operate. Some of them have built-in batteries, but even with those you usually get better performance with phantom power.

Another thing to note with the 3.5mm input is whether it's a stereo or mono input. Most of the 3.5mm microphone inputs I've seen are stereo. This connector looks identical to those found on a pair of headphones. A TRS connection has three connections, referred to as the tip, ring, and sleeve. For a stereo microphone input, that's going to mean, left, right, and ground. If it's mono, it will just have a signal and ground.

This is useful to know if you are selecting a microphone to plug into your input, not into an external preamp. You're going to need to know if you need a stereo microphone input, i.e. do you need one microphone to send a signal to both left and right? Do you actually need separate microphones? That's something you'll have to sort out. It may not work out plugging a mono microphone into a stereo microphone input or vice versa. It may not work at all, or it may even cause damage to your system.

So this is something you should double-check in the camera's manual. If your camera system is using XLR, the world's your oyster, and you can pretty much use any microphone you wish.

Conclusion

Coming up in the next part of this course, you're going to learn about several different types of microphones, starting with a shotgun microphone.

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