Shooting video with a Beachtek DXA-SLR

I recently got a Beachtek DXA-SLR at my job to shoot in-camera audio with the Canon 7D and Canon 5DmkII. I took it our for a test drive with a Sennheiser EW100 wireless lav kit. Set the EW100 to output at unity and the input of the transmitter set to -10db to be safe to not over-modulate the input.  I was pleasantly surprised at the quality of the preamps in the Beachtek. It seemed to have a good range of acceptable headroom without clipping. After I got the footage into the studio and started looking at the waveforms, I noticed that, while the monitoring of the Beachtek was clean, the Canon 7D’s AGC (Auto Gain Control) was still affecting the recorded audio. As any DSLR shooter knows there is a lot of ducking, compression and noticeable ”hiss” during quiet segments of your recordings. This is where the Beachtek’s “AGC Disable” feature comes into play. When enabled, it sends a 20khz (inaudible) tone out of the left channel of the Beachtek to the Camera, therefore keeping a constant level of audio feeding the Canon and not allowing the camera’s internal AGC to kick in. Now, with my Beachtek set to Stereo output, I had 20khz tone in the left channel and clean audio in the right. With a quick stereo filter in Adobe Premiere Pro (Fill Right) I now had great sounding in-camera recorded audio.

I noticed that when you set the Beachtek to mono output with the AGC DSBL Engaged you will end up with [the 20khz tone + PGM audio] in the left and [Clean PGM Audio] in the right. *See waveforms. As long as you are using the “Fill Right” filter trick, you can set the Beachtek to mono output. That way when you are monitoring the unit on set you get a nice clean mono send to both your headphones and not the mix and match effect you hear when it’s set to stereo.  

Beachtek DXA-SLR Webpage