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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.
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