Canon 7D/T2i AGC Bypass Trick OMG duh!

ChrisPrine said:
Juiced Link has a fancy pants version of this. A specialized noise generator. I think it's supposed to reduce chances of crosstalk
http://www.juicedlink.com/
Click to expand...


Fancy pants version with a few extra crucial features. First, I believe it does reduce any chances of crosstalk. But it also adds level monitors, and a headphone jack. These are two very important elements to the adapter.

Then again, I may be bias, since I actually own one of these with a JuicedLink CX231.

But it works beautifully. Just extract the right channel in post and make the left channel centered. The sound quality out of the CX231+DN101 is astounding.
 
Do you think it'd be possible to make your own headphone output for monitoring?

How would putting a headphone splitter before the ipod plug affect the sound quality? Does splitting the signal put half of the signal in one cable and half on the other?
 
OK, I think I'm a doofus. :huh:

I can't get the AGC bypass "trick" to work with the T2i. Here's my set-up:

T2i
VideoMic
iPhone/MP3player
Dual (3.5mm) mono jacks to single (3.5mm) stereo y-adapter plug
mono to mono cable
Stereo to Stereo cable

1. Load sound file onto iPhone/MP3 player with:
a. 20Hz or 20kHz tone; or
b. White noise at a constant -6db.
2. Plug y-adapter into "Mic In" on T2i.
3. Plug VideoMic into y-adapter mono jack 1.
4. Plug iPhone/MP3 player into mono jack 2 using:
a. m-m cable; or
b. s-s cable.
5. Turn everything on.
6. Record - "Testing..."
7. Get nothing but HISS-s-s-s-s/noise (verified in software; using SB CS3).
8. Test different volume levels, realize nothing works, discover futility of efforts and pull out hair!!!

Guys, I'm doing something wrong. Do I need a mixer for this to work properly? Are the connections/cables/adapters right? Is there a (maybe hidden) setting that needs changing?

Anybody get this to work effectively? If so, help a brother out please!
 
Record one clip with the mic unpluged and you should be getting just the tone? yes?

Are you able to record the tone at all?

record another clip with the mp3 player unpluged and you should be getting hissy mic (hissy when not talking to the mic) yes?

I'm thinking maybe the Y adapter might not be seated or a correct L and R mono(female) to sterio male????


"20Hz or 20kHz tone" why not just dump a "bars and tone" clip from cs3 and render the audio out to an MP3? Can the camera hear 20Hz or 20KHZ tone correctly? I don't know about using white noise, seems like a bad idea to me.
 
White noise or tone are on both tracks... only once was I able to get (sorta) clean sound from the mic, but I forget the exact configuration I used

Now it really sounds like the wrong Y or serious crosstalk (not likely)
How about a mono line from the mp3 player to mono into the Y adapter?
 
videohog said:
Record one clip with the mic unpluged and you should be getting just the tone? yes?

record another clip with the mp3 player unpluged and you should be getting hissy mic (hissy when not talking to the mic) yes?
Click to expand...

Not sure. Will try it out and get back to you.

I'm thinking maybe the Y adapter might not be seated or a correct L and R mono(female) to sterio male????
Click to expand...
It's a dual mono jack to stereo plug adapter. Each channel is labeled "M" though, not "L" and "R". Maybe this is the problem?


"20Hz or 20kHz tone" why not just dump a "bars and tone" clip from cs3 and render the audio out to an MP3?
Click to expand...
I think 20Hz or 20kHz are ideal tones because:

http://en.wikipedia.org/wiki/Psychoacoustics#Limits_of_perception

At an adequate level, either tone should be able to suppress the AGC, without being overtly audible... in theory. :badputer:

Can the camera hear 20Hz or 20KHZ tone correctly?
Click to expand...
Not sure. Will read the manual.

I don't know about using white noise, seems like a bad idea to me.
Click to expand...
It's what the JuicedLink DN101 does to suppress the AGC. And it costs $140 + can only work with a JL mixer.

videohog said:
How about a mono line from the mp3 player to mono into the Y adapter?
Click to expand...

Tried it. Doesn't work (for me).

I'll keep testing, but honestly, I think I'm just going to get a little recorder anyway and record sound seperately, until Canon/MagicLantern (possibly) comes out with a firmware update. I really don't mind syncing in post. :)
 
Just one more observation while I was trying this.

I noticed that the stereo mic plug on the camera (1/8 inch) is not very strong, so when I plugged in my "Y" adapter and the cable from the XLR mic (with the downconvert to 1/8 inch)
The weight of just the Y connector and the mic cable would cause the connection to be broken intermittently whenever you moved anything (cam, mic, any kind of movement on the cable etc) which may have been your problem.
I think I'm going to hardmount the mp3 player, XLR mic and cable and the Y adapter to somewhere sturdy (not on the cam) and the only connection to the cam will be a small light 1/8 inch stereo extender cable.
 
Hope that works for you. I was using a Rode VideoMic and a small MP3 player, in a controlled environment, so the stress on the connection was pretty insignificant.

Until then, it's dual system sound for me. Just waiting for my tax refund to come in. :)
 
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