Wednesday, March 24, 2010

Sennheiser MKE 400 + Canon 5D Mark II

The Canon 5D Mark II Firmware 2.0.4 finally allows manual control of the audio recording level in 64 steps. The audio preamp inside the Canon 5D Mark II is not the greatest but if you set the rec. level low i.e. 1, 2 or max. 3 steps above zero audio hiss practically disapears.

I find the Sennheiser MKE 400 signal at the "+" setting just a little too low to be used with the 1, 2 or 3 rec level of the camera. I didn't want to add a third battery to the system therefore I had the idea to boost the signal using an audio transformer. My solution boosts only one channel following an old sound recording trick. If you set one channel about 6 dB lower than the other you minimize clipped audio because when one channel clips you will most probably be able to use the -6 db one. Since the 5D Mark II doesn't show audio level meters during video recording such a safety net is very welcome.

I have no experience with audio transformers so I virtually tried my luck and bought a specs wise good looking shielded 1:2 audio transformer from RS-Components. The part number is 667-6044.
The shielded Z21805C 1:2 (6 dB) audio transformer is made by Oxford Electrical Products. Here's the data sheet. It has a very wide frequency range and low distortion and it doesn't add any noise. I think any quality transformer with similar specs will do.

I also bought a ready made stereo 3.5mm plug to socket cable and used a short piece of both ends.

To my surprise this simple solution works very well. Soundtrack Pro reports a 5 dB difference between the channels. The noise floor of a recording in an absolutely quiet room is at -65 dB at both channels (using rec. level 1 of the 5DMKII) and is practically not audible. It's a huge difference to the annoying hiss in the former AGC only recordings. I have no means to measure the audio quality but I can't hear any difference between the two channels other than the volume. For many applications this quality will be good enough and double sound is no longer mandatory.


  1. Hi I just bought the audio transformer but having difficulties working out on the pins' combinations to solder the Input & Output cables.Appreciate you could help to number the 9 pins and advice exactly the right pins to solder the cable. A simple and clear diagram will help. We tried to zoom closer to the picture of your transformer but could not see clearly the connections. Thank you for sharing.Regards Kam.

  2. Kam, if you bought the same transformer you can use the detailed hand drawn diagram shown above. You need to download the Z21805C Data Sheet from the RS-Components web site to figure out the pin numbers.

  3. Hi Martin, thanks for the replies and advises.
    It seem that the component's pin no.6 is faulty.
    Now waiting for a replacement and will seek your advise, should we face any technical's problem.Appreciate your generosity in sharing.