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Using two sets of lavs on a Canon T3i. How to input?

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Harry Bromley-Davenport
Using two sets of lavs on a Canon T3i. How to input?
on Oct 13, 2011 at 6:39:07 pm

I have ordered two little signal boosting devices (Fiio E5) in order to use my two sets of Audio Technica Pro 88W R wireless units with the Rebel T3i. So that should reduce the somewhat hissy background noise I am experiencing when using one radio lav.

But now I want to either purchase, or have a special cable and mini 1/8th stereo plug made up, that will take the signal from each wireless receiver and route each mike to one leg of the camera's stereo input.

So this would be a "Y" arrangement, with each radio receiver feeding one side of the camera's stereo input.

Questions:

1. Had anyone done this?

2. Is there a ready made cable that I can buy off the shelf?

3. Are the two channels of audio on the Rebel 3ti "discreet" channels - that is to say, for instance, does the on-board compressor/AGC control both channels simultaneously or are they separate circuits.

Thanks so much for reading this convoluted description. Your help would be appreciated. Canon, naturally, have no idea what I'm talking about.

Best,

Harry.



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Eric Toline
Re: Using two sets of lavs on a Canon T3i. How to input?
on Oct 13, 2011 at 7:18:37 pm

The AGC is global meaning both channels. You'll need a custom cable with the correct connectors for your wireless feeding a 3.5mm TRS connector with one wirless connectd to the tip or left channel and the other to the ring or left channel.

Recording audio on the camera is not going to give you good results. What you should do is get a small recorder like a zoom something and put the audio on that and sync everything up with pluraleyes.

Eric


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Harry Bromley-Davenport
Re: Using two sets of lavs on a Canon T3i. How to input?
on Oct 13, 2011 at 7:38:20 pm

Thank you very much for your prompt reply.

I am aware that the Canon T3i is far from ideal as a sound recorder. However, on my current project there are times when I have no choice. I do use Pluraleyes normally.

Thank you for the information about the AGC being global, which is what I suspected. But I am assuming now that the 2 channels on the T3i can be used for individual recording when in manual gain control mode.

With thanks,

Harry.



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Ty Ford
Re: Using two sets of lavs on a Canon T3i. How to input?
on Oct 14, 2011 at 1:54:59 am

Hello Harry and welcome to the Cow Audio Forum,

I can't comment on the AGC issue, but the cable below will connect two balanced XLR sources to a stereo 1/8" TRS INPUT.

http://www.trewaudio.com/store/product.php?productid=147&cat=21&page=1

Regards,

Ty Ford

Cow Audio Forum Leader
Want better production audio?: Ty Ford's Audio Bootcamp Field Guide


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Harry Bromley-Davenport
Re: Using two sets of lavs on a Canon T3i. How to input?
on Oct 14, 2011 at 2:36:27 am

Dear Mr. Ford.

Thank you very much for your prompt response.

I am currently feeding the 1/8 inch output from my little Audio Technica Pro88 wireless receivers into the XLR inputs of my Canon XLH1 using two accessory cables that Audio Technica call "CP8306 Transformer balanced adapter cable to use PRO 88W receiver with XLR-type balanced microphone inputs."

So I imagine that if I connected the above XLR balanced outputs from the receiver to the Canon T3i's 1/8 inch stereo input via the cable that you have kindly suggested, the trick would work.

But I can't help feeling that going from the unbalanced output from the wireless receiver, through the Audio Technica transformer, and then into the Y adapter in your link (which has another transformer) might be a bit of overkill - and might perhaps introduce noise/hums and whatnot. But perhaps I am wrong?

Also $72 is not cheap. But if you think it will be satisfactory, I will take your advice and buy it.

Might it not be simpler to connect direct from the two wireless transmitters which have 1/8 inch mono outputs to a 1/8 inch stereo jack, with one mike on the tip and the other mike on the ring?

As you can no doubt tell, I am not an audio professional. So I am not familiar with this field.

If you have any further comments or ideas that might help me achieve my goal with the maximum sound quality and, perhaps, a little less expensively, I would be most grateful.

With thanks for taking the time to reply,

Harry.



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Eric Toline
Re: Using two sets of lavs on a Canon T3i. How to input?
on Oct 14, 2011 at 2:48:21 am

You don't need all that extra stuff & expense. The receiver output is unbalanced and the camera input is balanced. All you need is a cable wired for an unbalanced XLR. If your handy with a soldering iron it's easy. The positive/audio signal from the receiver go's to pin 2 in the xlr, the ground/shield gets connected to pin 1 & 3 in the xlr. For $20 each I'll make you all you want.

Eric
audioetc@bellsouth.net


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Harry Bromley-Davenport
Re: Using two sets of lavs on a Canon T3i. How to input?
on Oct 14, 2011 at 3:09:42 am

Dear Mr. Toline,

Thank you again for the response.

The receiver output is unbalanced - that much I know. But I have the impression that the external audio input to the Canon T3i is also unbalanced, no? It's a 1/8th inch tiny little stereo jack input.

I really can't tell from the camera's manual or the Canon specs whether this little stereo audio input is balanced or unbalanced.

I guess that if it is indeed unbalanced, it would be a simple matter for me to solder up a Y connector which takes the mono signal from each wireless receiver and connect the signal to the tip and ring of a stereo mini 1/8th inch jack plug.

Do you reckon that's the correct drill for my situation?

The only thing I am still vague about is whether the camera's external audio input (the 1/8th inch stereo socket) is balanced or unbalanced.

Thank you again for taking the time to help me with this matter which I am sure, to you, is very simple.

And yes - I can wield a soldering iron after a fashion.

Best wishes,

Harry.



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Eric Toline
Re: Using two sets of lavs on a Canon T3i. How to input?
on Oct 14, 2011 at 2:37:16 pm

1/8" or 3.5 mm connections are unbalanced.


Eric


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Harry Bromley-Davenport
Re: Using two sets of lavs on a Canon T3i. How to input?
on Oct 14, 2011 at 6:09:35 pm

Unbalanced. Excellent. Thank you very much.

Best

Harry.



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Ty Ford
Re: Using two sets of lavs on a Canon T3i. How to input?
on Oct 14, 2011 at 2:54:53 am

Hello Harry,

The cable I speced has no transformer. The blocking capacitor prevents bias voltages generated by the camera (if any) from getting back into the receiver.

If the wireless receiver you have has an unbalanced out and you can find a y cable that uses tip for one side and ring for the other, you should be OK if the camera input is, in fact a stereo unbalanced input.

The issue concerning ALC remains unsolved.

Regards,

Ty Ford

Cow Audio Forum Leader
Want better production audio?: Ty Ford's Audio Bootcamp Field Guide


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Harry Bromley-Davenport
Re: Using two sets of lavs on a Canon T3i. How to input?
on Oct 14, 2011 at 3:15:19 am

Dear Mr. Ford,

Ah. I see. No transformer.

It looks as if I will give it a shot by making up a simple Y cable as you suggest. I will live in the hope that the camera is not generating any of these mysterious bias voltages to which you refer.

If I hear nasty noises, I will have to look into the blocking capacitor solution.

And I have found out about the AGC. The two channels are linked when AGC is active.

Thank you very much for the assistance and suggestions.

Harry.



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Ty Ford
Re: Using two sets of lavs on a Canon T3i. How to input?
on Oct 14, 2011 at 3:33:32 am

My Dear Mr. Bromley-Davenport

If the ALC can be bypassed, please do so for your and our listening enjoyment.

Cheers,

Ty Ford

Cow Audio Forum Leader
Want better production audio?: Ty Ford's Audio Bootcamp Field Guide


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Harry Bromley-Davenport
Re: Using two sets of lavs on a Canon T3i. How to input?
on Oct 14, 2011 at 3:34:19 am

I know what you mean. Agreed.

Many thanks,

Harry.



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Victoria Trestrail
Re: Using two sets of lavs on a Canon T3i. How to input?
on Dec 14, 2011 at 2:27:27 pm

Hi Ty,

I just got the Rebel T3i and my first project is to record a live concert.

There is a blue xlr audio feed cable coming out of the mixer in the audio booth (that is also where the camera will be set up).

I was just wondering if you could tell me the correct cable to use to connect the T3i to the xlr and possible send me a link?

Thank you so much for all your help.

Victoria


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Andrew Rendell
Re: Using two sets of lavs on a Canon T3i. How to input?
on Oct 15, 2011 at 12:09:51 pm

Have you considered Magic Lantern? I have it on my 550D (T2i) and not only are there a few things that improve the camera for video, it can also turn off the AGC and give you manual audio level control plus it also has the option to use both sides of the stereo input mini jack for balanced audio (although only one track, obviously).

YMMV - Magic Lantern does a few things differently on the different models of DSLR, so have a look on their website.

Incidentally, I've got a Fiio E5 and it's great as a headphone buffer (which is what it's designed for) but I hadn't thought of using it for a microphone feed.


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