16Feb What DSLR audio interface is right for you?

Gordon wrote in:

With all the different models of Beachtek and JuicedLink adapters it’s hard to figure out which one is the most suitable as a direct to dslr camera audio solution. What’s your favorite?

Above are just a few of units I have laying around the studio so it’s hard for me to pick a favorite. Others I have that aren’t pictured include the Juicedlink CX231, , and the . Some of these companies like Beachtek (left) and Studio1 (center) discontinue models and release replacements almost every year which gives us a lot of older units to choose from, while others like Juicedlink (right) have had a mostly consistent product line over the years. I’ll try to answer the question by describing each type audio adapter I use and what uses each type are best suited for.

Most of these companies started out making XLR adapters for DV and MiniDV cameras like the GL2 and VX2000 which (for their time) shot great video, but didn’t include proper XLR inputs. Many of these early adapters were passive. This basically means that the unit has no way to increase the volume of an audio signal, instead it is only designed to attenuate (fancy word for decrease) the level of the audio before it enters the camera.

Passive XLR audio adapters are usually and often sell for well under a $100. Even though many of them were designed for MiniDV cameras, they still work very well with any DSLR that has adjustable input gain settings. For Canon users the 5d mark II with the latest Canon firmware, t3i, 60d, and the t2i with Magic lantern firmware work, but Canon provides no love for the the 7d.

These passive XLR adapters work best with strong audio sources such as wireless receivers, self powered microphones, and field recorders. These adapters also allow you to send each audio input to the left channel, right channel, or both channels of your camera’s stereo input. Most of these passive adapters are created equal and as long as it provides a G1-G2 switch (Ground lift), S-M switch (stereo/mono), and large volume knobs you’ll be fine. I use these passive adapters mostly for wireless mic level control, but they are also a great way to feed the audio from a Zoom h1 or h4n into your camera’s audio input.

Next up are the active powered audio adapters. Active audio adapters are sometimes called a preamp and provide gain using internal amplifiers which are usually powered by a 9 volt battery. Some of the active XLR adapters like the Juicedlink CX231 also provide phantom power for boom mics like the BP4073 and MKH-60 that require 48v power to operate. If you need phantom power for a microphone this is probably the most convenient way to provide it in a small package.

One of the main benefits of an active adapter is that it provides clean audio gain. A camera has a lot of stuff inside and it’s often hard for the manufacture to provide top quality audio amplifiers in such a small space. The active adapter allows you to turn the camera’s less optimized audio amplifiers down and use a device that is dedicated to audio for amplification.  You can delve deeper into this subject if you like but basically gain from a preamp into your camera is usually better then trying to increase the audio levels inside the camera itself. I generally use an active audio adapter when I’m recording from an audio source like a boom mic or a hand held microphone like the SM58.

Juicedlink is kind of the king of active audio adapters. Every camera mount audio adapter they make has a built in preamp with around 30db of gain. Beachtek has only two models that I know of that provide a preamp, the DXA-SLR and DXA-SLR pro, both of which provide about 15db of audio gain. The only complaint I have about Juicedlink adapters is that the adjustment knobs are way to small for my large hands. This makes it harder for me to make quick adjustments to audio levels while filming.

Last but not least are the audio adapters that provide AGC (automatic gain control) disabling functions. The Juicedlink DS214 (above) is one of the few examples of an active audio adapter without XLR inputs. It also provides an AGC disabling function.

Automatic gain control is a system built into some cameras that monitors the input levels of the audio being recorded by the camera and then makes automatic adjustments to the volume in an effort to maintain a preset audio level. AGC doesn’t cause much of a problem when the audio source is at a consistent high level, but when audio levels drop off, the automatic gain controller tries to turn the level of the income audio up to reach its preset. This usually shows up as loud hissing noise between the gaps in dialog when recording.

To defeat this effect an AGC disabling function sends a strong audio signal to either the left or the right channel on the camera. This tricks the camera’s gain controller into thinking that it has a strong signal causing it to turn the input level down considerably and keep it there. The AGC disabling unit then sends the input audio to the opposite audio channel. The result is one channel of audio with a useless band of noise on it, and the other channel with clean usable audio. In post you simply convert your recorded audio to a mono track of the clean audio recorded into either the left or right channel of your camera.

This method is not ideal, but it’s probably your best bet if you’re a Canon 7d owner, or have a t2i and don’t want to install Magic Lantern firmware. Juicedlink and Beachtek both make several adapters that have this feature but I don’t often use it unless I have to. That’s mainly because the cameras that require this fix don’t offer you any way to properly monitor the recorded audio. This means you could finish filming for the day and find out later that the audio turned out poorly. Then it’s either overdub and rebuild all the audio from scratch, or film the whole thing over.

So why do i have two DS214 audio preamps if I don’t use the AGC disable function? It’s because the DS214 is a great audio preamp and has audio level controls for the left and right channel. This means I can plug something like the Rode VideoMic in and set the left channel to one level and the right channel to a lower audio level.  Chances are very good that when the left channel clips because someone starts screaming on set (had no idea it was coming because I didn’t read the script) the right channels audio will be set low enough to avoid peaking. This sort of protection has saved a project more times then I should have needed it to, so I use it when every possible.

I have a video on that trick if you’d like to find out more click here. If you have any other subjects you’d like me to cover in this much detail, just drop me a line. Thanks for question Gordon!

Tags: Audio adapters, Beachtek DXA-2S, Beachtek DXA-SLR, Beachtek DXA-SLR Pro, BP4073, DSLR audio, Juicedlink CX231, Juicedlink DS214, Juicedlink DT454, OpTex DXA-4