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Old June 24th, 2012, 09:47 AM   #1
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Record three lavs with 2 audio input camera

I have to record three lavs but my Canon XF305 has only two external audio inputs.

What is the easiest way to record 3 into 2?
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Old June 24th, 2012, 09:56 AM   #2
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Re: Record three lavs with 2 audio input camera

This is why they make audio mixers. Is this a one-off need? Do you need to acquire a mixer for future productions? What is your budget? What microphones, camera, etc. are you using?
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Old June 24th, 2012, 11:18 AM   #3
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Re: Record three lavs with 2 audio input camera

As I said in my original post, I am using a Canon XF305 camera. The microphones are Sennheiser. I don't anticipate needing to use 3 mics in the future and would like to spend as little as possible. I would also like to keep it as simple as possible as it is a one-man shoot.
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Old June 24th, 2012, 11:38 AM   #4
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Re: Record three lavs with 2 audio input camera

Buy a Zoom H4N or some other cheap audio recorder that takes XLR. Run two to the camera and one to the recorder. Sure you will have to sync them together later but it is a much better solution than trying to mix down to 2 channels and dealing with phasing issues (depending on distance of course).
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Old June 24th, 2012, 01:51 PM   #5
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Re: Record three lavs with 2 audio input camera

Also check out the Tascam DR-40 - field recorder accepts XLR (with phantom power) for less than $200.
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Old June 24th, 2012, 05:23 PM   #6
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Re: Record three lavs with 2 audio input camera

Quote:
Originally Posted by Bob Prichard View Post
I have to record three lavs but my Canon XF305 has only two external audio inputs.

What is the easiest way to record 3 into 2?
Rent a mixer from Trew audio in your area.

Cheers.
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Old June 24th, 2012, 05:58 PM   #7
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Re: Record three lavs with 2 audio input camera

Have to agree with the others use a mixer, as another alternative that hasn't been mentioned use a second camera this will then give you 4 inputs (2 on each) as well as some variations of shots, it will make the production a whole lot more interesting rather than just a single camera fixed shot or zoom in-out.
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Old June 24th, 2012, 06:04 PM   #8
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Re: Record three lavs with 2 audio input camera

Quote:
Originally Posted by Bob Prichard View Post
I have to record three lavs but my Canon XF305 has only two external audio inputs.

What is the easiest way to record 3 into 2?
Another second for the suggestion to rent a mixer. The Sound Devices 302 is purpose-built to do exactly what you're asking for.
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Old June 24th, 2012, 06:34 PM   #9
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Re: Record three lavs with 2 audio input camera

I hope you aren't going to run those mics in 'Auto' gain are you?

The best option is hire a soundo to do the job properly... the chances are they will have better mics than you have, they will do it properly, position them correctly, actually monitor them and ride the levels, save you hours in post production, reduce your headaches, less stress for you, make you look good to your client who will recommend you to others which will in return get you more work.
It will be a win for you at a small price.
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Old June 24th, 2012, 08:15 PM   #10
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Re: Record three lavs with 2 audio input camera

While I agree with using a mixer, I have done this type of thing a few times when the job changes mid-stream. Like when I get there and "oh, BTW we nned to run 3 mics, not the 1 or 2 we originally said". I have 2 ways to control that set up without resorting to a mixer which again is the right way to do it.
First my receiver is the AT1821 which is a dual channel receiver and I can mix mics 1 and 2 to go to the same side of the reciever which mean I only need to use 1 XLR cable from the receiver to the camera leaving the other XLR input open on my camera so I can then run another mic BUT prior to my having the AT unit (I was an early buyer of it and I don't remember how long ago I go it) I used 2 invidual receivers so I would end up using a "Y" cable. Plug the 2 xlr cables off the individual receivers into the "Y" cable then plug that into the camera then have an open xlr connection on the camera for my 3rd mic.
Ideal? Nope. Workable? Yep. For some run and gun types of works it's the only way and it produces relatively decent audio. Would I do it for critical type work? Not a chance but in a pinch you do what got gotta do using what you got or you go home.
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Old June 28th, 2012, 09:01 PM   #11
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Re: Record three lavs with 2 audio input camera

Don,

Thank you for your thoughtful and informative reply to my question.

I followed your example and purchased a 2 into 1 XLR adaptor so that I could run 2 of the mics into one input, and use the second input on the camera for the third mic.

The problem that I have run into is that the sound level on the mics that are run into the Y-cable is much lower than the mic that runs into the second input.

I tried switching the mics around, and the problem was consistent, regardless of the mic (I have all Sennheiser wireless lavs).

Did you have this problem with your Y-cable, and if you did, what was your fix?
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Old June 28th, 2012, 09:54 PM   #12
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Re: Record three lavs with 2 audio input camera

I never really had that problem but then I almost always run my audio manually so I could adjust on the fly.
I never ran wired lavs and I don't run an XF series camera but I used the Y cable on a JVC5000U which only had 1 rear XLR (don't ask why) and the levels were very consistant. I ran that on PD150s and PD170s as well with constant levels between the 2 XLRs but again I run mostly manual so I just might have never noticed a difference.
If you're running AGC is there an adjustment in the menu somewhere for the 2 different channels so you can get them close? Also how much difference is there?
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Old June 29th, 2012, 07:23 AM   #13
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Re: Record three lavs with 2 audio input camera

Quote:
Originally Posted by Bob Prichard View Post
Don,

Thank you for your thoughtful and informative reply to my question.

I followed your example and purchased a 2 into 1 XLR adaptor so that I could run 2 of the mics into one input, and use the second input on the camera for the third mic.

The problem that I have run into is that the sound level on the mics that are run into the Y-cable is much lower than the mic that runs into the second input.

I tried switching the mics around, and the problem was consistent, regardless of the mic (I have all Sennheiser wireless lavs).

Did you have this problem with your Y-cable, and if you did, what was your fix?
'Y' cables are absolutely the wrong way to go. Doing so puts the mics in parallel with each other so they load each other down and screws up the impedance the mic input sees. 'Y's are okay for splitting an output but rarely work well for combining into an input. Better to use a proper combiner such as this one ...
Whirlwind IMCOM - 2-to-1 Microphone Combiner IMCOM B&H Photo
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Old June 29th, 2012, 07:31 AM   #14
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Re: Record three lavs with 2 audio input camera

In my experience (which is certainly "old school" and based on theory rather than just "trial-and-error") it is considered bad practice to connect two (or more) outputs together.

For example, if you connect the left channel and right channel speaker outputs of your power amp together, and then start driving stereo signal through the amp, you are likely to blow the output transistors.

Even in a low-level situation, such as connecting two microphones directly together, or the output of two teceivers directly together, you are likely to run into problems. (Interestingly, this was probably less troublesome 50 years ago, with tube equipment, than it is today with solid state.)

I won't go into all the technical details here (unless someone asks later) but suffice it to say that one aspect of this problem is related to the output impedance of the devices. For example, a mic might have an output impedance of 200 ohms, yet be specified to feed a load impedance of 1000 ohms or greater. So if you connect two mics together, each one is feeding its signal into the other 200 ohm mic (in parallel with the preamp input), an combined impedance which is much lower than the specified 1000 ohm load. That will make the level lower than expected (by several dB) and can also cause unexpected distortion.

So if you're trying to connect two mics, two receiver outputs, etc., you should not use a simple "Y" cable. At the very least you need to know the impedance of the devices in question, and the "mixing" cable should be constructed with correct resistors to prevent the sort of impedance mismatch and mis-loading described above.

Now... can you use a simple "Y" cable? Yes. Will it work somewhat? Probably. Are you likely to have some problems? Yes, definitely, and they are hard to predict without knowing about the specific equipment and situation.

EDIT: Steve H, it looks as if you and I were both thinking and typing the same thoughts at the same time. You beat me to the finish line. ;-)
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Old June 29th, 2012, 07:58 AM   #15
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Re: Record three lavs with 2 audio input camera

For a few dollars more than the combiner buy a mixer....

Rolls MX124 Portable 4 Channel Stereo Mixer MX124 B&H Photo

OK its not a "sound devices" but its way better than a 'Y' cord and far more usable for the future
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