BeachTek

Sound has always been one of the biggest stumbling blocks for HD-DSLRs.
XLR adaptors for cameras are nothing new. Beachtek and other companies have been doing them for donkey’s years. The Canon 7D, 1DmkiV and 7D have big problems with sound. The input being a puny 3.5mm jack is of course fixed by these XLR adaptors which has Balanced Audio. This is where Beachtek comes in to resolve this problem. The following explains why Balance audio is better and how AGC affects your audio recording.

What is the difference between balanced and unbalanced?
Most professional audio devices are connected via balanced cables to minimize pickup of stray electrical noise. Consumer audio devices use unbalanced cables and are very prone to picking up noise, especially at low signal levels from devices such as microphones. Balanced circuits have an inherent ability to only pass audio signals and reject unwanted noise. Balanced refers to the fact that there are two symmetrical signal lines and one ground, while unbalanced uses just one signal line in reference to ground. Normally, XLR connectors are used in most balanced devices while unbalanced consumer gear normally use mini-plug connectors.

Automatic gain control (AGC)
Automatic gain control (AGC) is an adaptive system found in many electronic devices. The average output signal level is fed back to adjust the gain to an appropriate level for a range of input signal levels. For example, without AGC the sound emitted from an AM radio receiver would vary to an extreme extent from a weak to a strong signal; the AGC effectively reduces the volume if the signal is strong and raises it when it is weaker. AGC algorithms often use a PID controller where the P term is driven by the error between expected and actual output amplitude.

An audio tape generates a certain amount of noise. If the level of the signal on the tape is low, the noise is more prominent, i.e., the signal-to-noise ratio is lower than it could be. To produce the least noisy recording, the recording volume should be set as high as possible without being so high as to clip or seriously distort the signal. In professional high-fidelity recording the level is set manually using a peak-reading meter. If high fidelity is not a requirement, a suitable recording level can be set by an AGC circuit which reduces the gain as the average signal level increases. This allows a usable recording to be made even for speech some distance from the microphone of an audio recorder.

A potential disadvantage of AGC is that when recording something like music with quiet and loud passages, the AGC will tend to make the quiet passages louder and the loud passages quieter, compressing the dynamic range; the result can be a reduced musical quality if the signal is not re-expanded on playback, as in a companding system.

Separate recorder

External recorders are used all the time on professional Hollywood sets, where they have the team of people dedicated to the audio.

Here are some situations where I find using a Beachtek low-noise preamplifier to record direct to the camera is much more convenient than using a separate recorder:

• Missing the shot. Digital recorders can take a time to boot up when you power them on. That boot up time feels like an eternity when you're waiting to try and capture a spontaneous moment. If you are ever doing any kind of run-and-gun, then this delay (including fumbling around to get to the right menu) can cause you to miss your shot.

• Forget to capture the audio. You hit record on your H4n, you hear the vows being spoken through your headphones, and you think you're all good. The problem is you're not actually recording to the media at this time. You need to hit record a second time before the H4n starts recording the audio to the media. You only need to press Record on your DSLR to have the sound recorded. (Not three times, one for the camera plus twice for the H4n).
• Save time and hassle in post production. When you record your audio separately, then you will need to synchronize it with your video in post production. This can be done, and there's even software to help you do it. However, the time and hassle increases exponentially with large numbers of short clips. Note that many of the new DSLR video cameras are only capable of short clips in the first place.
• Go home with the confidence that your "shot is in the can". When you record your audio separately, your clients will not have the experience of reviewing your audio and video together, until you have torn down the set, paid your actors, and returned home to synchronize your audio and video together in your computer.
  • If there was a dog barking in the background, or an air conditioner vent turned on in the middle of your scene, then it's too late to go back and recreate your scene.
  • When you record your audio and video together in camera, then you can review them together on location to verify that everything is good, before you tear down your setup.
  • Note that some cameras (such as DSLR cameras) do not have a headphone jack. So, you would use an external monitor plugged into the camera's AVout jack to review your audio and video together, on location.

Beachtek DXA-2T (Low Range)

The 2 channel DXA-2T is easy to setup and use. It’s suited for users with a tight budget and yet wishes to have professional audio. The Beachtek DXA-2T allows filmmaker to connect professional microphones with balanced XLR connectors to any Camcorder or DSLR that has a Microphone Jack. The DXA-2T gives you all the benefits of using balanced audio devices for noise free operation as well as complete control over the signal levels to ensure best possible sound recording.

Since the adapter is a passive device, it is completely noise free and the premium transformer ensures superb audio. It also features dual trim controls that allow you to adjust the input levels independently. This small little device is made of Rugged Die Cast aluminum encase in a rubber boot which makes it reliable and dependable in the most demanding situation.

Beachtek DXA-5DA (Budget Range)

The DXA-5DA is suited for users with a slightly higher budget and wants slightly more control over the audio. The DXA-5DA is a two channel, transformer balanced XLR adapter for attaching external microphone and other audio gears to any DSLR or Camcorder that has a microphone jack.

The Beachtek DXA-5DA features a built in level meter to show the input strength at a glance while trim controls allow you to adjust the input level for optimum recording. It also features a headphone jack that allows you to monitor the audio coming out of the adapter.

A unique feature that the DXA-5DA has is the ability to control the wild swings of the Auto gain control that plague most cameras. This dramatically reduces noise during quiet moments of recording.

Beachtek DXA-SLR (High Range)

The DXA-SLR is the top of the range XLR-adaptor in its class. The DXA-SLR is suited for Professionals. The DXA-SLR has 2 channels, active XLR adapter with built in Preamplifiers for attaching external microphones and other audio gears. It can be use with any Camcorder or audio recording device that has a microphone jack.

The DXA-SLR lets you connect a wide variety of audio devices including wireless systems, sound board and professional condenser microphone that require 48 volt phantom power to operate. Another new feature is you are able to monitor the audio via the headphone jack during recording and playback.

A unique feature that the DXA-SLR has is the enhanced AGC Disable feature works even better at controlling the wild swings of the Auto Gain Control that plague most cameras. This dramatically reduce the noise during quiet moments of recording allowing you to record two channels of clean audio.

Current compatible models in the market

Sony VEG-10

Sony HXR-MC50P

Sony HVR-HD1000

Sony HDR-FX7E

Sony HDR-XR550E

Sony HDR-CX550E

Sony HDR-HC9E

Canon EOS-500D

Canon EOS-550D

Canon EOS-60D

Canon EOS-7D

Canon EOS-5D MK II

Canon EOS-1D MK IV

Canon Legria HF-M32

Canon Legria HF-M31

Canon Legria HF-S200

Canon Legria HF-S21

Canon Legria HF-M300

Nikon D-90

Nikon D-300s

Nikon D3s

Panasonic HDC-SDT750GC (3D)

Beachtek will work with most Camcorder or DSLR with Microphone Jack.