Author Topic: Results of audio tests with ML and Canon 550D, T2i  (Read 5828 times)


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Results of audio tests with ML and Canon 550D, T2i
« on: September 10, 2012, 09:34:18 PM »
I spent some time testing audio with my new ML software and 550D.  Firstly, after you disable the AGC, you are virtually left with a line level input -- not really a mic level input -- in the Canon's mic 3.5mm input.  This can either be good news or bad news, depending on how you look at it.  I tested this by first plugging my battery operated Sony ECM-979 electret condenser mic into the input with the AGC off.  It's nice, but the signal is way too low.  I boosted the analogue gain up to 32db (max) and the output volume to max.  The digital gains just add noise, so there's no point in using them.  The analogue and output gains don't add any noticeable noise, but the signal is still way too low. So, again, it's not much help calling this a mic input without the AGC, which seems to do all the work--badly.
This simply means that the camera's input is not set up to correctly boost a mic signal up to line level (sometimes a boost of some 60db is required).  This mic (Sony) also has a nice signal with the ACC on and lots of gain, but the AGC is too noisy--and not only noisy but adds a not-so-nice pre-amplification.
Next test was to take the MAIN OUT L/R from my little Mackie 402-VLZ3 mixer at LINE LEVEL into a 3.5mm jack for the camera's input.  I used a studio Rode NT2 condenser (phantom power on).  I set the Mackie to Unity gain at the mics INPUT GAIN, at the VOLUME FADER, and at the MAIN MIX out: Unity gain simply means that after the mic is pre-amped by the Mackie's mic preamp  that the input and output are at the same gain -- like it's not adding level.  This test recording was beautiful: The camera was quite happy to accept the LINE LEVEL signal.
I did set zero on the ML analogue gain, digital gain and output volume (and yes, the output volume does affect the main signal strength, and is not just for headphones as some have stated in Internet blurbs).
So the good news is that if you use an ENG mixer ( not the Mackie as it isn't battery powered) you can simply come out at LINE LEVEL if you keep the faders down: punching the faders up too far would cause overload.
And the bad news is that unless you have something like the Rode Videomic with its 20db boost you aren't going to get quite the required level from just plugging in a microphone with the AGC off.  You can get away with it if you boost the signal in post production, but I've noticed that this does add a little noise.
And it's a good idea to wait a couple of seconds after pressing the camera's record as the ML shoots out a big burst of audio whilst it's getting its act together.   

Malcolm Debono

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Re: Results of audio tests with ML and Canon 550D, T2i
« Reply #1 on: September 10, 2012, 09:52:37 PM »
Thanks for sharing these results! Definitely useful knowledge.

The best on-camera mic I've found is the Rode VideoMic Pro. It has +20db built-in which allows me to bypass the camera's noisy pre-amp and get decent ambient audio during events & weddings.
Wedding & event cinematographer
C100 & 6D shooter
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