Consumer Camcorder Audio Interface

Requirements

 Mic level and line level inputs
audio level indication
Audio Splitter
Miscellaneous adapter cables
Headphones as a final confidence check

Audio Mixer Options

There are nice dedicated camera audio interfaces from Juicedlink and Beachtek but at $500 each compared to ~$150 for a small mixer I think the mixer would be a better option.



https://www.storedj.com.au/products/BEH-Q802USB

http://www.smproaudio.com/index.php/en/products/di-boxes


http://www.juicedlink.com/
http://www.juicedlink.com/audio-preamps-mixers-etc-c-66/ra333-riggy-assist
$US469

Beachtek
Beachtek have a range of mic adaptors for camcorders. The lower end cheaper ones do not have level meters.  They used to do a unit called the DXA-4C that I assume was pretty low cost.

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Microphone Splitters

Questioning of industry types indicates that they often run the radio mics into the desk at mic level.  So to tap off at the radio mic interface, a splitter would be needed.  I suspect that at the more pro events that the PA supplier would provide that split but transformer isolated splitters are pretty cheap and so having one in the kit would be handy.  (The just look like a DI box.)

EWI MST-103 from Ebay or Cannon Onlie Australia   $60

ARX but I dont know price or where to buy

Miscellaneous Cables

I suspect some sound operators will not be keen on touching the wiring between the radio mic receiver and the sound desk.  I suspect they will prefer to provide a line out from the desk.  So we will need a couple of adapters to meet those requirements.
Probably
RCA->XLR(M)
Jack -> XLR(M)
Then run a mic cable to our mixer that we would locate at our camcorder.

Mounting the shotgun Mic

The Camcorders do not have a shoe.
This web site has innumerable brackets.  Some of which should go between the tripod and the camera.  There are presumably other similar web sites and shops or there is always bunnings and DIY.

Fallback, we can use a mic stand.

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26-09-2013 Testing Testing
It seems not so easy to record audio via the 3.5mm mic input connector.  It seems disproportionately noisy.  Part but not all of the problem is that the camera has AGC (Automatic Gain Control) and when the audio goes quiet say when the speaker pauses the camcorder increases the gain and hence the noise goes up.
We have two problmes

1. The thing is simply too noisy anyway
2. The AGC makes it even more noisy in the quiet times.

 Now I wonder if those guys who sell these dedicated boxes (juicedlink and Beachtek) do some trickery to defeat the AGC.  For example shove in a tone above or below the audible range.

This article from juicedlink infers that Beachtek use a 20kHz tone.  Ah so smart.  I wonder what Juicedlink do?  Ah here they tell us they inject broadband noise onto one channel which becomes unusable and sets the AGC level of the other channel.  I think I prefer the Beachtek version.  I wonder if Beachtek have patented it.
So I think the next thing to do is to see if I can borrow a Beachtek interface.  If it is still noisy then there is not much point in continuing down this path.  Beachtek show two distributors in Australia.
http://www.johnbarry.com.au/
http://www.videoguys.com.au 

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Tuesday 1-10-2013 Lab Test
Did some tests with a 20kHz tone and two microphone sources.
The two microphone sources were:  1) The radio lapel and 2) the mini shotgun.
Used the PC to generate a 20kHz tone.
Tried various combinations of feeding the tone in one channel and feeding a mic on the other channel or the same channel.  When fed on the same channel, the 20kHz was combined with the mic at line level using a RCA Y lead.  Yea I know dodgy.

Firstly the 20kHz tone sure quietens down the camcorder.

There is something too smart with the camcorder.  At times it will just switch back to the internal microphones even though the 3.5mm plug is plugged in and has not been touched.

There are times when about once a second it momentarilly glitches.  I think it is switching back and forth between the 3.5mm input.

It seems that having the white (Left I guess) lead connected to the RCA Y adapter and putting in the 20kHz tone and the radio lapel mic receiver and the Red (Right I guess) connected to the mixer & mini shotgun seems to be the best option.  Mind you the mini shotgun and mixer are themselves a bit noisy.  Eithe way it is heaps better than without the 20kHz tone and there may be some improvement if I track down the source of the noise from the mini shotgun and mixer.









Microphone Pre-amp circuits

http://www.eeweb.com/blog/extreme_circuits/balanced-microphone-amplifier