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DSLR Audio Trick for Canon 7D and T2i

Here’s a quick and inexpensive way to trick the automatic gain control (AGC) in a DSLR from increasing the volume during the quiet parts of your recording.

It only works on cameras like the Canon 7D and T2i which have a microphone input. Also, the AGC function is just one reason the audio recorded on these cameras is less than great.

Pro audio recorders capture the sound in high resolution. Meaning that they use high sample rates and more bits per sample to capture a more accurate version of the sound. DSLR cameras use moderate sample rates with much fewer bits per sample.

What this means is that the audio may sound okay until you start to work with it in post production. Then, just like a poor quality video image, you’ll find you can’t do much with it.

So, give this trick a try to improve the quality of the audio recorded in your DSLR HD camera. And, if you’re out to make a film that you want to be as good as possible, spend the time and money to capture the sound with a professional microphone and recorder.

Yes, you have to lock the second audio track to your video in post but the results are well worth the effort.

{ 21 comments… add one }
  • Dan McComb May 26, 2010, 2:07 pm

    I tried this out following your directions on my T2i, and it doesn’t work. Maybe the T2i is different from the 7d? For whatever reason, when I plug in the radio shack splitter, nothing works plugged into it – neither the mic nor my iphone playing the tone. I just get a scratchy hissing sound.

    • adriel May 26, 2010, 2:35 pm


      If it’s not working on anything it could be a bad splitter. Maybe check with Radio Shack to see it it works on anything there and replace it.

      I’ve got a T2i on order. I’ll try it out and let you know.

      Anyone else try this on a T2i?

  • Dan McComb May 26, 2010, 3:27 pm

    I figured it out: I wasn’t using mono cables running from my iPhone to the splitter. With a mono cable, it works great. Same is true from the mic – it needs to be hooked up with a mono cable upstream from the splitter (the cable supplied with my Sennheiser Wireless G3 doesn’t work because it’s a stereo cable).

    • adriel May 26, 2010, 3:48 pm

      Great, thanks for getting back to us. Let us know if this improves the audio on your T2i.

  • dave April 21, 2012, 2:07 pm

    this is bull

    • adriel April 24, 2012, 7:41 pm

      One man’s trash is another’s treasure…

      I’m firmly in the dual audio camp even though I have a T3i with manual audio controls. But some people have found this technique useful.


  • James February 1, 2013, 7:11 am

    An interesting point, but the sample rates actually make no difference, most dslr’s can record audio at 44.1khz, this by the nature of basic sampling theorem can capture the entire bandwidth required, i.e. hearable by a human. refer to Nyquist-Shannon for the full run down.

    The bit depth can make a slight difference, most of these cameras can only record at 16bit, but i think the analogue end limits the dynamic range more than being at 16bit.

    So basically, its just not true, onboard camera mics sound terrible because of everything but the sample rate and bit depth. An external recorder will sound better because its analogue circuitry is better, the mics plugged into it will be better, and being separate from the recorder allows you to position them better.

    A common misconception you have here but, high resolution does not make recordings sound better, during processing and some post stages, it might, but a clean dry recording of the real world, makes no difference.

    Feel free to email me if you’d like more information about it.

  • Ross Rosenberg January 13, 2014, 11:55 am


    I am trying to figure out a way to run two microphones into my canon t2i.  Any advice would be GREATLY appreciated.  Thanks!

    Ross Rosenberg

    • Adriel Brunson January 13, 2014, 4:57 pm


      You can use a “Y” cable as a kind of reverse splitter. The “Y” needs a stereo 1/8″ male plug to go into the camera and two mono 1/8″ female connectors to plug the microphones into. One mic will be on the left channel and the other on the right channel. That being said, I do not recommend this approach with a T2i.

      There is no audio level control on a T2i so you will not be able to adjust either mic. To run two mics into almost any recorder or device you’ll be best off with a mixer. That will give you independent control of each microphone. And, if you’re using a mixer, I recommend feeding it to an external digital recorder for best results. You can also feed the audio to your T2i as a reference track. But the audio recording in a T2i is much lower quality than even a $100 Zoom H1.

      If the audio is important enough for you to use two microphones, I suggest that it’s important enough to justify the use of a mixer and a digital recorder.

      Thanks for stopping by, let me know how it goes.


      • Ross Rosenberg January 13, 2014, 5:03 pm

        I just called a video specialist at a local camera store who recommended the Azden Cam3 3 Chanel mixer.  http://www.azdencorp.com/wp-content/uploads/2013/04/cam3pic4.jpg

        Do you think this will be a suitable solution tothe problem?  Thank you for the help/advice.

        Ross Rosenberg

        • Adriel Brunson January 14, 2014, 1:46 pm

          The Azden Cam 3 mixer may do the trick nicely. Inputs 1 and 2 are mono and assigned to the left and right channels permanently. Input 3 is stereo so you may not use it for a two mic recording. Note that this is a passive mixer. It has no batteries and does not amplify the incoming mic signal. It does allow you to lower the volume of a mic that’s too loud but no boosting one that’s too low.

          Again, the audio recording on the T2i does not allow manual control of the volume so you’re putting decent sound into a less than great system. I still recommend picking up a Zoom H1 for the audio recording in addition to this mixer. That way you can use the input control on the recorder to set the volume for the quietest mic and use the mixer to pull down the volume on the louder one. Head phones will let you monitor the sound from the H1 so you can be sure to get a good recording. No head phone output on the T2i.

          Search for reviews of the Azden Cam 3 on Amazon or B&H photo and you’ll get a good idea of how this device works. Let me know how it goes!


          • Ross Rosenberg January 14, 2014, 1:53 pm

            Would the Zoom 1 device connect to the camera?  If it doesnt, How would I synch the sound tothe video?  Thank you so much for your help! 

          • Adriel Brunson January 14, 2014, 2:04 pm

            Use this cable – Sescom LN2MIC-ZMH4-MON 3.5mm Line to Mic 25dB Attenuation Cable for Zoom H4N with Headphone Monitoring Jack  (affiliate link)

            Plug it into the headphone out of the Zoom. Your headphones go into the female connector and the male goes to the camera mic in. It has a built in attenuator that cuts the headphone signal down to mic level.

            You just have to remember that any change you make to the headphone output of the Zoom will also change the audio on the T2i. But if you’re just using the T2i track for reference to sync up later that’s no big deal.



          • Ross Rosenberg January 14, 2014, 3:11 pm

            Thank you!  I will let you know how it all works.

  • Lily October 12, 2014, 8:07 pm

    I did this with my Canon 7D and it definitely worked. Thank you so much!

    • Adriel Brunson October 13, 2014, 3:08 pm

      Thanks for letting me know, Lily.


  • abbas October 27, 2015, 7:51 am


    is it work on canon 700d(t5i)????

    • Adriel Brunson October 28, 2015, 8:55 am

      Yes, this should work on a Canon 700D – T5i. Give it a try and let me know how it goes.



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