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I work as a sound designer. Sometimes I do dialogue recording for short films. But honestly, I never use a field mixer or portable mic preamp. I only ever use a handheld (Zoom H4n or Tascam DR) and a shotgun mic (Rode NTG 1).

I've recently done a lot of research on the internet about field mixers, and I'm starting to understand basically how they work.

But I'm finding it difficult to learn about gain control when using 2 or 3 shotgun mics.

That's why we use a mixer isn't it...? to mix 2 or more dialogue tracks down to 1 track?

So I'm thinking there must be some technique to control the gain

  • Which mic should be louder?
  • Which mic should be softer?
  • What are the standards used to decide it?

Can anyone help with information... links, references?

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A mixer will have multiple channels for your multiple inputs.

Each channel will have a trim pot (gain knob) for adjusting the input level.

(Sidenote: some channels may not have a trim, those are line-level inputs, not mic-level inputs, and they are meant for things that already at "line-level")

You set your gain as you need to for each channel, nothing more or less. The only real standard is "don't clip the channel." (Unless it sounds good... but really, for what you're doing, don't clip anything)

You generally don't want to be making crucial mix decisions in the field. Ideally, you will be using direct-outs from the mixer, but you can also utilize the various bussing options (auxes, sub-groups, matrices, left and right channels, etc.) to isolate your signals as much as possible.

Those outputs are then generally sent to a multi-track recorder which captures the individual sources for use later. The actual mix is postponed, just as the video edit isn't done on the fly.

That said, you absolutely can (and may have to), make some final choices while shooting. This may be because you have a limited number of recording inputs, or because your mixer doesn't have enough outputs. Whatever the reason, it means you'll have to do some mixing in the field.

In those situations, you just do the best you can. Use your ears and mix the signals in the best way you know how. Consider not only what you are hearing, but the tools that can be used later as well, along with what you think the finished product should sound like. Hopefully you're only having to mix a couple tracks together, so you'll only need to worry about the balance of say, two things, as opposed to thirty things. Just consider that small piece in the broader perspective of the full puzzle.

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The use of a field mixer is not restricted to mixing several sources into one track. It is often used to send individual sources to individual tracks.

When you need to mix several sources into one track in a live dialogue recording situation, you have to dynamically deal with each of the sources as the shot goes by. Having sevral microphones continuously open usually leads to poor results.

Example 1 : one shotgun on a boom and several lavalier microphones. You will have to deal with opening and closing smoothly each of the lavalier when the character it is used for is speaking/not speaking, and deal with the ratio of boom you want to add on top. A common use case is using a stereo mixer, where you would send the boom on one side and a mix of lavalier on the other side.

Example 2 : one main microphone on a boom and others microphones hidden on set for particular parts of the scene. You will also have to deal with opening the hiden microphones only when they are useful, unless you want a lot of undesirable artifacts on your sound take.

There are today several manufacturer of multitracks field recorder that allow to record each individual source on it's own track and deal with the mix at the post-production stage. This technique can prevent unfortunate choices on stage and offer a wider choice when dub mixing. But it can also make the post-production workflow more complex.

To sum it up : there's no theoretical technique to set up the gain (apart from not overloading your channel and recorder) but a lot of practice and know-how to be able to deal with live mixing of several sources.

  • Thanks for your great explanation .. it help me a lot to start undesrtand this .. How about the time code ? say that im gonna use 1 shotgun and 1 Lav, and im not gonna blend it to one track .. so i will have 1 track of shotgun and 1 track of Lav .. and when i immported it to my DAW, Did they will Sync ? i mean, if there are any track that slide, it will be a problem ... – ClueSeeker Feb 12 '15 at 8:22

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