Line Out ≠ Mic Input

When I started this blog post my intentions were to solicit help from the community, however before I finished writing, I found my answer. I’m hoping this makes its way into the abyss of the Google indexes and helps someone like me in the future.

This week I have to do a video shoot at the office. During our test shots, I decided I didn’t like the audio quality I was getting from the camera and the wireless mic. So, I decided to incorporate my home studio gear and run some additional tests.

The gear: 
Canon VIXIA HV30 (HDV to tape with microphone input)
MOTU Traveler (multi track mixer/firewire interface)
Numerous Microphones (condensers, bullets and wireless lavalier)
Audio-Technica ATR288W (wireless tx/rx kit)
MacBook Pro

My intentions were to mix the audio from multiple microphones using the MOTO as a mixer and piping a cable back into the camera’s microphone input. I know you recording pros are probably asking why I didn’t take each mic to a digital track via firewire? After all that’s what the MOTU does best. Well, I don’t have the software tools necessary (limited to iLife ’08) to capture video and multi audio tracks at the same time. I guess I could attempt to simultanously record in GarageBand and capture video in iMovieHD (or ’08), but syncing would then be an issue. You get the point.

For the life of me I couldn’t figure out why the audio sounded great via the Headphone on the MOTU, but crap from the Headphone on the HV30. After hours of fiddling with knobs and levels, I had just about given up, when I decided to take the mixed audio and run it into the wireless trasmitter/receiver then into the HV30. Bingo! Everything sounds great, but why?

As it turns out Line Level is not the same as Mic Level. Line level (technically +4dBu) is a standard level used by many pieces of audio equipment like DVDs, Tape Decks, and in my case a Mixer. Mic Level on the other hand assumes the signal is much weaker and boosts/amplifies it. This explains why my line level audio was so distorted. Apparently the wireless kit accepts both Mic and Line Levels, and then outputs the correct Mic Level.

If you are in need of piping mixed audio into your camera’s Mic Input, you will likely need to convert the signal. There are sources for this like BeachTek (no affiliation and never used them) or a wireless kit like the one I used.

BTW, I don’t claim to be an expert at this I’m just a mass consumer of technology. If you see an error, leave a comment. If you have something to add, leave a comment. If you have read this far, leave a comment. If you are alive, leave a comment. 

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