Hedging my bets with a mixer

[Benjamin Margulis]

A friend of mine asked me an interesting question. He wants to know if I can feed the raw signals from my mixer into his camera.

I honestly don't know the answer to this one, so I figured I'd come here.

I was thinking that perhaps I could send it through my AUX-Send output...but on the other hand since it's Post-Fader I'm not sure that it will be seperate signals - I'm thinking that it's more likely than not the mixed sound.

I'm working off of a Behringer EURORACK MX602A mixer, just in case you guys would like to know that.

On the other hand, would it just be better to use Y-cables to split the signals before they even REACH my mixer and feed the raw audio into his camera?

Thanks for any and all advice,
Ben

[Matt Ockenfels]

Benjamin,

Which camera are you using?

Cheers,

-Matt

[Benjamin Margulis]

He's using a Canon GL2 along with the MA-300 adapter - it adds two XLR inputs.

Hope that helps.

Ben

[Mark Burlingame]

I don't have a GL-2 but I am pretty sure that camcorder accepts both mic and line level inputs so the direct feed (line level) from the mixer should be fine. Mark

[Steve House]

Watch out for possible level mismatches and overloading of the camera's audio inputs. The camera line-in sensitivity is the consumer -10dB while your mixer's outputs are designed for pro +4dBu level. You might need to insert a pad in the line between the two to match the levels.

[Matt Ockenfels]

I agree with Mark and Steve. When you try first try this out, set the mixer so that its not passing any sound, do the connect and set the camera's audio input to maybe halfway.

If the mixer generates tone, start with that. When you're ready to start, bring the mixer level up SLOWLY. Watch/listen to the camera levels.

If the mixer level is up halfway or so, and your levels seem reasonable on the camera, its time to do some camera input level adjusting and you're set. However, if the levels increase too rapidly or are distorted, the pad that Steve mentioned is required (of course make sure that if the mixer output is LINE, than camera input is set to LINE as well.)

Also, if the mixer output is unbalanced (Single Tip 1/4" plug or RCA-type phono jack) be sure to use the unbalanced input on the camera (not the XLR adapter)

I realize this is pretty general, but I hope it helps!

Cheers,
-Matt

[Benjamin Margulis]

Thanks everyone who responded.

I'm going to experiment a bit with the equipment, bearing all that you've said in mind.

Ben

[David Ennis]

Ben,
I own a GL2 and have done a lot of audio work with it including taking inputs from mixers as well as making some actual measurements of its audio input characteristics.

The GL2's input cannot handle a line level signal. It will distort with anything more than 14 milivolts (-37 dB) using its MIC ATT OFF setting, or with anything more than 120 milivolts (-18 dB) using its MIC ATT ON setting. And the MA300 is for mic level only also.

I'm not familiar with your board, but if it does have a -10 dB line level you will need about -25 to -30 dB of attentuation to use it with the GL2's MIC ATT ON. If the board has a +4 dBu line level out you will need about -40 dB of attentuation.

Your friend sounds new at this too, so tell him not to be fooled by the fact that he can adjust the GL2's manual audio gain controls to get good meter readings even without attenuation. The GL2's meters indicate recording level, not input level.

[Steve House]

I haven't worked with a GL2 so I'll defer to your experience but I could have sworn I saw in the specs that there was an auxillary line-level audio input available via a stereo mini-plug. Grabbing a copy of the manual from the Canon site shows numerous line-level audio copying, recording, and dubbing arrangments using the A/V In/Out jacks on the rear right-hand side panel (pp100-110). They also list audio line levels in the specs. Is that input not available in lieu of the mike in when shooting video?

[David Ennis]

Maybe it's me who misunderstood. I assumed that Ben want to record a live audio track to go with live video. That would have to be though the cam's mic jack, which accepts mic level signals only.

If he just wanted to record some audio he could do that through the AV port with the cam in VCR mode, at line levels as you said.

[Jay Massengill]

The MX602A has no Insert or Direct Out jacks. It has the single Aux Send jack, but that is a mix of post-fader signals that are routed to the Aux Send by each input's Aux Send control.
The other output jacks are the Main Out and the Tape Out, which carry the same signal. And the Control Room Out, which can carry either the main signal or the Tape In signal.
So you can't send the raw mic signals out to a separate device like you can with a Mackie 1202-VLZ, which has non-interrupting direct outputs for the mic channels. These jacks are only affected by the preamp and trim control on each input and are as close as you can come to being raw and still going through the mixer.
However, since the MX602A only has two mic inputs and these can be panned hard left and right, this will keep them separate as they travel to the Main Outputs. If you need to keep more than two signals separate from each other and send them to two separate destinations, you're out of luck.
You can use a splitter ahead of the mixer, but passive splitters can weaken the signal and active splitters are expensive.
What kind and how many signals are you trying to do?
Back to the camera input levels question. The outputs of this mixer are a full +4 level (even the Tape Out RCA's) unbalanced signal on a jack that will still work with a balanced cable. The easiest way to hook up would be to use either an XLR adapter with line-level attenuators built-in or use passive direct boxes between the mixer and the MA300.

[Steve House]

Originally Posted by Fred Retread

Maybe it's me who misunderstood. I assumed that Ben want to record a live audio track to go with live video. That would have to be though the cam's mic jack, which accepts mic level signals only.

If he just wanted to record some audio he could do that through the AV port with the cam in VCR mode, at line levels as you said.

That's what I meant - is that camera such that feeding audio into the aux in while shooting video doesn't override the mike in jacks? I would have thought that plugging into that jack would disconnect the mike inputs. I've been studying up on the XL2 prior to purchasing one and it has a switch that lets you select between either the front on-camera mike in, rear XLR mike in, or the rear Audio2 (RCA jacks) line-level input as the audio source when shooting video. (Do wish they'd have provided balanced line level inputs at the XLR jacks though.) The Aux Audio in on the GL2 won't serve the same purpose as the Audio2 line in on the XL2 and allow you to record audio from there instead of the mike when shooting?

If that's the case, Shure and other make pro quality attenuators to drop line levels down to mike levels to resolve Ben's problem, but I must say I'm surprised to hear that about as relatively a high-end camera as is the GL2.

[David Ennis]

The GL2's A/V port is for input in VCR mode and for output (for instance, to connect to a monitor) in Camera mode. The GL2 is half the price of the XL2, so I'm not surprised that it would have a little less flexibility. Do other cams in the $1500 to 2500 price range accept audio through the line inputs when recording video? I haven't checked.

[Benjamin Margulis]

Jay:
I'm feeding most probably two or three inputs (depending on what hardware I have available). I'm feeding a raw signal from a stage mic and a stereo signal from the sides of the room (for audience reaction).

[Steve House]

Originally Posted by Benjamin Margulis

Jay:
I'm feeding most probably two or three inputs (depending on what hardware I have available). I'm feeding a raw signal from a stage mic and a stereo signal from the sides of the room (for audience reaction).

Suggest you set the camera to 48kHz/16bit (ie, 2-channel) recording. Take the 2 stereo chanels and pan left channel to hard left, right to hard right, and mix the stage mike into both stereo channels equally, pan centre in other words. Feed the mixer out through an attenuator to the camera left and right input. Full line level out from the mixer will overload the mike level camera inputs for sure if you don't. Here's a link to Shure's inline pad -

http://www.shure.com/accessories/a15la.asp

BTW, the 602 only has two mike level inputs and it sound like you need at least 3 (left, right, and stage). Maybe time to get a new mixer :)

Also watch out for phase effects if the stereo pair of mikes are separated on each side of the room. The same sound arriving at the mikes at different times can create issues.