Microphone pre-processor for a Canon 7D

[KrisKasprzak]

All,

I think my idea will work but could use some guidance in feasibility. I often shoot video interviews using my Canon 7D and a powered lapel microphone. Getting audio levels correct is a real pain since the camera will not show a UV levels during video recording. I can buy a device that goes between my powered mic and camera and shows UV meters and level adjustment. I'm a DIY kinda guy so... I want to build one using my teensy. Here's how I think it can be done.

1. use a Teensy 3.2
2. connect it to the audio adapter board for the teensy
3. connect my mic to the input of the audio board
4. connect the output from the audio board to my camera (I don't see a jack but assume there is a connection point)
5. connect my 2.8" tft LCD to the teensy 3.2 to show spectrum of the output to the camera)
6. have some volume control so I can adjust the level that is being sent to the camera (and monitor the spectrum with the display)
7. if enough pins are left use touch on the display to let me adjust the volume, etc. (i've been very successful in getting ILI9341 displays to work, with SD cards, touch).
8. use one of the spectrum examples that Paul supplied with the Audio-master library--maybe show some cute spectrum of voice plot like in the waterfallSpectrum example
10. maybe have some headphone output so I can listen to what's actually being recorded
11. Note my lapel mic is mono, so I guess i'll split split it to left and right before processing


Some initial questions
1. I'm not really sure what voltage levels "line out" are and if my Canon 7D will be compatible with the levels from the teensy audio board, anyone know?
2. the output from my lapel mic is powered (meaning it has some small batteries inside it), is the output considered "line in" and be compatible with the teensy audio board?
3. I'm guessing connect my mono mic to the L/R channels on the input of the teensy audio board and leave the L/R output to go directly to the Canon camera


Thanks in advance. I've never messed with audio processing so this is uncharted territory for me.

Robin, here comes an order for 2 audio boards

 

[KrisKasprzak]

I just watched the audio tutorial and now 100% convinced that my project can be done with this very cool Hardware. Can't wait to get my audio boards in. PS this is not an April Fool's joke either

 

[GremlinWrangler]

Re line level see https://en.wikipedia.org/wiki/Line_level, your camera manual may have some information where it just talks voltages/impeadances that or very similar to that. Your camera is probably using the levels internally but if they have not provided a jack finding them and getting a suitable connecter in the case may be a serious adventure.

With the mic some mic designs require power but still produce a mic level output (but with low introduced noise over pure passive mics) checking the information for it will give some information there. Or try it on line input and see how it works, unlikely to cause
harm (reverse of line out levels into the mic IN of the audio board is not a good idea).

With mono->stereo possibly the best way is to feed just the left channel and then split left/right digitally after all the processing. Doing it by connecting the mic to both left and right input works, but will not be a good impedance match and mean doubling up all the processing steps.