Need help with mixing boards

[Erik Larsen]

Good afternoon to you all. I am very new to the world of digital video and especially to the audio production side of it. I just got an XL1s this summer and I have a small project coming up around the holidays where I will be shooting a choir concert at my church. I want to record the audio from the choir mics, directly to the camera via the sound board. This is so that I don't have to use the on-camera mic. I tried a kind of test run recently during a regular service. Before hand, I asked the gentlemen who operate our sound system how to get a feed from the board to the camera and that's when I discovered that they don't really know anything about the system or the equipment except how to adjust the volume and how to put a tape in to record. Not wanting to waste an opportunity to practice my skills I settled for using the camera mic (and got all kinds of junk as you might have expected).

It is clear to me now that I will need to learn how to operate one of these boards myself. Can anyone direct me to good resources (Internet sites, books, etc.) to learn about how these things work? I tried to find something in the library, but I couldn't seem to find anything on the subject. Should I try searching "Audio Mastering" or "audio engineering" or any ideas? I would be most appreciative. Otherwise, I will have to spend a Saturday learning by trial and error (that was our sound guys suggestion) and that likely won't be good for me and may even screw them up.

Sorry for being long winded. Thanks in advance.

[Martin Garrison]

I would start by reading the manual. If your church doesn't have it you can probably download it from the manufacturer.

I don't have much experience with the xl1s, but I believe it can record through rca type line-ins. Most boards will have "tape outs" that will be -10db line level rca jacks. If these aren't already in use I would try to run stereo rca cables from these to your camera. Should be a perfect match.

If they are using these to run to the record device, you may try taking a pass through off of the recording device.

Do you know what kind of board it is?

[Erik Larsen]

Thanks for the quick reply. It's funny, but it never even occurred to me to read through the manual. Duh! I will be over there tomorrow and see what I can find, and see if I can find a make and model number. I seem to recall there being some RCA plugs on the back side of the board but a didn't understand the labelling conventions on them. For example, is a "return" an output? Anyway, I tried using some of them last time and didn't seem to get any input in the camera (the audio monitor on the cam registered nothing).

By the way, this reminds me of a couple other questions I had. First, will volume adjustments on the board, either for a certain channel or for the main output get translated to the input for the cam? And how do I know the input level on the camera is good? I know everyone recommends checking for the audio using headphones at all times, (newbie moment appraoching) but since there is a volume control for the headphones, how do you know you are getting it right in the cam. I mean, I could be getting not quite enough recorded volume, but it seems like it because the headphones are turned up. Is there a range on the on board audio monitor that I should be looking at? Do you set headphones at the middle volume setting and leave it there to judge incoming audio? Forgive me if this sounds stupid to you guys. I'm still learning here and trying to get it right sooner rather than later. Thanks again.

[Martin Garrison]

In field work, the things you should be listening for in the headphones are mainly:

1)distortion...your input is too hot and your peaking either the mic pres of the camera or the circuitry. OR your levels are too high and your clipping the recording.

2)unwanted noise...could be from any variety of problems, environment, mic placement, electrical hum OR your levels are too low and signal is not overcoming the inherrant noise floor of your recording device.

So, turn up the headphone amp, so you can get a good picture of what's being recorded, just don't hurt your ears. Also use your meters. The best way to set levels would be to get a tone from the mixer and set that at -12, then have them pass through something loud and make sure it doesn't peak.

The master volume level of the board will control some but not all of the outs, to some extent it depends on the board. Same with the input levels, but not the gain knobs, they are always in effect. Check for "pre/post fade" in the manual.

FYI "returns" usually denote an input, but where there are returns there are "aux sends" which can act as a seperate mix and will have a master fader(or knob) of thier own.

Remember, your not listening for volume, you can adjust that later. Listen to see if the sound is the sound you want, and if the signal is clean.

[Paul Tauger]

Mixing boards are pretty straight-forward, and they all work the same.

A return takes the input from the effects send. This is either a single or stero output that goes to your effects chain (reverb, etc.). You can vary the amount of signal from each channel which gets sent to the effects send.

The output from the effects chain is fed back to the mixing board through the return (which is almost always a stereo input), so that you can vary the amount of applied effects.

The output of the board goes to the input of the camera (assuming you want the mixed sound recorded with the image -- you may not). The board will have at least one pair of stereo outs, which should go to the stereo in on your camera. Note: these are line-level, not mike level, so make sure your camera accepts, and is set to, line level input.

The best way to monitor audio input is a combination of phones and keeping an eye on the level meters -- pro and prosumer cameras should allow monitoring audio level. If you're using a mixing board, you probably want to disable the AGC on the camera. Otherwise, you may get a "pumping" effect in the sound as the camera tries to keep levels even.

You didn't ask, but one other input which might be confusing you is labeled "insert". An insert comes before the the input signal is modified by the board's EQ. Use insert for comp/limiters on specific input lines, e.g. the talent's microphone, etc.

Some other mixing board terminology, as it occurs to me:

Pad: a switchable attenuator that limits the input level of a specific source, e.g. if you're using a speaker output from another audio device to input to your mixer (be VERY careful doing this, as you can blow both devices).

Sub in: These are inputs that bypass the "mixing" portion of the mixing board. Use these for pre-mixed and balanced signals, e.g. from another mixing board, or from a tape deck, etc.

Fold back: This is a separately attenuable, i.e. you can vary the output level without effecting mix, output that is used to provide a signal to monitor speakers so that the talent can hear the music they play. This is essential for singers who need to hear the music they're singing to. You can set a separate fold back mix, which will be output to a fold back amp and speakers. The audience can't hear the fold back (if you've done it right), but the talent can. Nothing is more frustrating for a singer than to not be able to hear the music; fold back insures that they can.

Snake: This is a bundled cable that will take all the inputs from the mikes and bring them to the mixer. A snake is a great time and labor saver, as you don't have to run each mike line all the way back to the mixer. The snake consists of a box at one end with a bunch of input jacks, a long thick cable, and a series of plugs at the other end.

XLR: Trust me, you want to use mikes wired for XLR, and use XLR jacks on the mixer. XLR is a plug format that accomdates balanced lines. Without getting into a long explanation, a balanced line will eliminate hum that would result from long mike line runs. A second advantage of XLR connectors is that they are very secure -- they snap in and aren't easy to dislodge.

Program out: This is what you may want to feed to your camera (assuming you want to record audio with video). This is the sum total of the mixed audio signal, before it goes to the amplifiers. Note that what is mixed at the board may not necessarily produce good audio for your camera, as it will be balanced for what sounds good for the house mix. For example, a good house mix is equalized to eliminate feedback based on the particular aural qualities of the hall. This may entail a sharp cut-off of a particular frequency or frequencies. Also, the house mix may have overly-boosed bass or treble to compensate for the speakers used. You may wind up with over-saturated bass or treble on your soundtrack that will have to be fixed in post.

I know this isn't what you want to hear, but if you want really good sound for your video, you may need to do a separate mix just for the camera.

Hope this helps.

[Ed Frazier]

Hi Erik - If you can't find the product manual, as suggested above, try the manufacturer's website. If you hit a wall there, try www.mackie.com. Go to the Mixer section and then check the Product Documentation link on the Support page. There you can download User Manuals for just about all their mixers. That should help some, even if your mixer is not a Mackie.

I don't recommend experimenting with the equipment given the fact that the operator really doesn't know how it all works. You could easily screw up their settings.

You can get some sort of output from many points on most mixers. Levels at these various outputs may or may not be controlled by the Main Output controls. You really need the book for the specific board to know exactly what to expect. What you want will be labeled Main Out, Tape Out or maybe Control Room Out. Most other outputs will be for specific channels or groups of channels.

Levels also vary, depending on the output selected as well as the position of switches or buttons on the board. Again, the manual might be necessary unless the outputs are clearly marked. It is easy to exceed the input requirements on the XL1S if you are not careful. Make sure the output level matches what you have set on the camera. Inline attenuators are an easy way to match levels.

Once you figure it all out though, the audio will far exceed what you can get with the on-board mic.

Good Luck

[Steven Digges]

Eric,

Start with your XL1s manual. Your camera has many audio functions and options. If you do not get it correct at the record point the board settings will not matter. No offence, I'm guessing by your questions you may not understand all of those settings.

The best way for you to get this right is to go to a rehersal or choir practice when all of the gear is in use and record your own rehersal. The day of the real shoot, when you are all set up and have it correct, test it by recording anything you can get to tape (before the performance) and play that back while listening to your headphones and looking at the XL1s monitor. When you play tape back and listen with phones - what you hear is what you got.

Also, with digital audio, 0db means 0db. A low signal may be able to be recoverd, an over-modulated signal is most likely toast.

Good luck,

Steve

[Erik Larsen]

Martin, Paul, Ed, and Steven,

Thanks everyone for the great help. This is exactly why I spend so much time reading the posts here. I really appreciate your patience and willingness to help us DVInfants.

Martin: Thanks for the reply. Can you tell that I am still pretty unsure of myself at this stage? But I would rather ask you guys dumb questions than to never gain any confidence in what I am doing.

Paul: Extra thanks for the quick seminar. That is the kind of stuff I am trying to learn. It is obvious that we (at my church) need someone who understands such things. I can't imagine how they get by knowing so little. You mentioned that I might need audio that is mixed differently from the house mix to go to video, and while that "isn't what I want to hear", it is exactly what I want to hear. Otherwise I won't get better at this. Question though: does this require a second board? Do you take each individual mic signal from the house board (prior to any mixing) and route the signals to a second board where they are mixed for video?

Ed: I agree wholeheartedly about not experimenting with their board. If they don't know how to use is it, then I am guaranteed to screw it up and neither of us will be able to get it back. They offered to let me make a mess that they can't fix. Not wise. Thanks about the suggestion on the manuals as well.

Steven: No offense taken, especially since you are correct that I don't really understand all of my camera's capabilities yet. This is particularly true of the audio controls. I plan on being at the rehearsals, so I will definately get time to do this right.

I love learning new stuff like this and I can't wait to get to work on it. It is an exciting field, even if it is just a hobby (for now). Thanks again to you all.

[Steven Digges]

Eric,

There are no dumb questions. I have been involved in multimedia for many years and STILL ask question here that are elementary.

How many channels are they running on the board? If it is just a couple of choir mikes and one for the minister your best bet may be to go with the aux send. Look for an output labeled AUX 1 to go to your camera, you will have to adjust the aux send knob of every hot channel individually and also understand pre and post fade. If they are running many channels a program feed may be your best bet. Every situation is different. Not having a good sound man on the board is a big concern but it is also surprisingly common.

Here is the good news. Your XL1s can lay down 4 channels of audio. You can keep your on board mic hot on 2 channels for insurance and send your mixer feed to the other 2 channels. This way you will be guaranteed to at least have an audio recording if all else fails from the board. These tracks can then be separated very easily on output. I record this way quite often, and not just for insurance. When I am in post I sometimes mix the mic tracks in at a very low level for a natural sounding mix.

Keep posting. There are a lot of guys here that will help. What kind of board is it, how many hot channels? Etc. etc. etc. What are you shooting, a service or a drama presentation?

Steve

[Steven Digges]

Eric,

Here is another thought. Find a sound person to help the regular guy. This may be easier than you think. My son attends a Catholic School and is a member of the “Tech Club”, these kids run the board. He is better than many of the “technitians” I run into at my “professional” gigs. Is there a school associated with your church? I will guarantee you there is someone in your congregation that knows audio and may volunteer to help with this gig. You may find some guy that was in a band that hung up the guitar a long time ago but is good at mixing. You will be surprised by how many people have mixed at one time or another. Can you post in a church bulletin or make an announcement? It can’t hurt to ask. It sounds like the current tech on the board will not be offended, especially if you ask him first (real audio engineers will cut your arms off if you reach for a fader on their board, as it should be).

Steve

[Paul Tauger]

Erik, if the audio is properly mixed and EQ to balance the house is applied post mixer (which is the way it should be done), then you'll be okay. The problem is, most non-pro (and semi-pro) mixes fix house balance problems at the mixing board because (1) it's easier, and (2) it's cheaper, as it eliminates the need for a separate equalizer. If that's the setup you're looking at, you might consider either taking the signal at the sub-out (which your board may or may not have), or, if the fold-back system isn't used, taking a fold-back mix and applying EQ and effects either live or in post. It's been quite a while since I was up on the stuff, though I used to do sound and video for a yearly variety show. Since I was doing both, it was easy for me -- I mixed for video and through an equalizer on the program out to handle house balance.

[Tony Singh]

Take a listen to the system through headphones on the board. If the mix sounds ok to you, go ahead and get a stereo feed from the board. The main outs are probably already feeding the amps to the house. There should be either a secondary stereo output, or Auxillary outputs. If you take the Aux outs, they can be either prefader or postfader. In your situation, I would suggest postfader. The board may even have the ability to assign group outputs.

If we knew what make and model the board is, we could probably offer a definite suggestion as to how to obtain your feed.

[Roger Berry]

Thanks to all you guys, this has been a really interesting thread.

Eric, like you, I'm a newbie and am knocked out by the way people are willing to help here.

Paul, could you explain more about XLR or offer a link. I'd like to know about balanced outputs and how to wire these plugs. Is it the same principal as a humbucker guitar pickup, using reverse phase to cancell noise?

Thanks!

Roger.

[Paul Tauger]

Roger, unfortunately, I'm the wrong guy to ask about XLR. I know how to use it, but I don't know a lot about the theory. I think you are correct -- there's a reverse phase signal that cancels out picked-up interference, but I couldn't say for sure. All I know is that my mixing board has XLR inputs, and all my mikes are XLR. Running stuff using just 1/4" plugs and lines usually results in hum, though sometimes that can be fixed with ground lifters (that's another topic altogether).

[Martin Garrison]

Minor clarification. The benefit of the cables are that they are balanced. Instead of just a hot and a ground connection, they have a hot(+) a ground and a cold(-). This is created in a sending piece of gear, and removed in the recieving. Someone more technical than I will have to explain how this takes the noise out of phase with itself.

Almost all xlr cables are balanced, it's why they have three connections. But you can run an unbalanced signal down an xlr cable. Likewise there are 1/4" plugs that have three connections and can carry a balanced signal. These are known as tip-ring-sleeve(TRS) as each of these parts is an isolated connection.