Disabiling AGC with iPhone/touch...in this example, using Zoom H4n recorder

Started Nov 22, 2009 | Discussions thread
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Disabiling AGC with iPhone/touch...in this example, using Zoom H4n recorder
Nov 22, 2009

I purchased the Zoom H4N to be used primarily as an on-camera external mic for the Canon 7D with the flexibility of also using it as an off camera mic when needed. But the AGC was driving me crazy since Magic Lantern isn't avaiable to the 7D yet. But I finally figured it out! How to disable the AGC on the 7D:

1) downloaded a FREE program off Appstore for the iPhone called FreqGen that can generate a continuous 20Hz sound.
2) Buy a 6.3mm stereo plug to 3.5mm stereo jack adapter
3) Buy two 3.5mm stereo male/male cable

4) plug one 3.5mm stereo male/male cable from Zoom H4N headphone out to Canon 7D mic-in

5) Plug other 3.5mm stereo male/male cable one end to iphone headphone out and the other to the 6.3mm plug adapter and plug into Line 1 input on Zoom H4N

6) Start FreqGen app and generate a 20Hz sinusoidal sound with app volume at max and iphone volume set at 5 bars (this gives me no reduction in level when I have Auto Level turned on)
7) Set Zoom H4N headphone out volume at 50%

8) Record with Canon 7D and this successfully suppresses the AGC. I still hear a bit of noise but this is removed easily with post processing.

I can FINALLY starting making vidoes now with the Zoom H4N

Alternatively, for someone using just an external mic like the Rode Videomic, etc..., one can use a 2 female to 1 male 3.5mm stereo adapter and connect one end to the external mic and the other to their iphone/touch and do the same thing. Mind you, I have not tried the external mic method but I think it should work.

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