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BMC User Manual
READ THIS FIRST
There are frequent changes to the camera rmware, it is hard to keep up with
them all. Make sure to subscribe to the juicedLink Blog for updated audio
applications guides for new camera rmware releases.
NOTE JULY 2014: Blackmagic has released new rmware for all of their cameras
(4th change to the audio). Earlier, when the camera was not in the hands
of many experienced audio users, we provided application guidance on
what settings to use in the camera, and EQ settings in post. We are currently
booked, and will not have a chance to evaluate the new rmware for quite
some time. Today, there are many experienced users on the various forums
who can assist with camera settings. Thank you for understanding.
METER CALIBRATION: Since every camera has a different sensitivity sweet
spot, you will need to calibrate the meter of the BMC388 to the needs of the
camera.
• BMCC: With the BMCC, you will use Ultrascope. This blog post with
rmware v1.3 describes what settings to use in the camera for calibration,
and also describes a methodology to x the camera frequency response
in post. The meter calibration section of the Riggy-Assist User Manual
describes the procedure for the Riggy-Assist. You will follow a similar
procedure with the BMC388, using Ultrascope (instead of the meters
of the camera). Note, the BMC388 has eliminated the meter sensitivity
switch used on the Riggy-Assist.
• BMPC: The BMPC does not have Thunderbolt, so you can not use the
meters of Ultrascope for calibration. You will proceed with an iterative
test recording to determine the meter calibration. This video from the
Riggy-Assist User Manual describes this process (you can ignore the
discussion on AGC Disable). For the BMPC, we are using the MIC level
gain at 100%.
Videos
Videos are helpful to illustrate things that are easier to communicate
visually. However, these videos do not cover all of the details in their entirety. If
you need more detail, then please consult the written User Manual, below.
OVERVIEW
Watch this video for an overview of the inputs, outputs, signal routing, switchbank, and other features such as phantom power, audio bracketing, and
selective power-down.
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CABLING TO BMCC AUDIO INPUTS
The BMCC inputs are 1/4” phono, and the BMC366 outputs are 3.5mm
minijack. Watch this video to see what is necessary to cable up to the BMCC.
MOUNTING DIRECTLY TO TOP OF BMCC
The BMC366 mounts so nicely directly to the top of the BMCC. It provides
a low-prole on the left side, for shoulder mounted situations. It sends the
XLR connectors out the right side of the camera (for similar reasons). When
mounted, it is as if the preamp is an integral part of your BMCC, like it had XLR
connectors right from the start. Watch this video to see how to mount the
BMC366 to the top of the BMCC.
MOUNTING TO DIY122B BMCC TOP MOUNTING PLATE
The DIY122B BMCC Top Mounting Plate provides a cost effective way of
mounting lots of accessories to your BMCC. Watch this video to see how to
mount the BMC366 to the DIY122B.
Quick Start Guide for Single Microphone
• METER CALIBRATION: Refer to the “Read this rst” section at the top.
• MOUNT TO TOP OF BMCC AND CONNECT AUDIO CABLES/ADAPTERS: This
process is best communicated visually. Please watch the “Cabling to
BMCC Inputs” and “Mounting Directly to Top of BMCC” videos above.
• GROUND LOOPS: The previoius mounting/cabling procedure is designed
to make sure that the only ground connection between the preamp and
the camera is via the audio cables. So, set both Balanced GND OUT and
ENC GND switches to the NORM position.
• POWER: Insert a fresh 9V alkaline battery into the battery tray in
the correct orientation. Set LiPoly/ALK to ALK. Turn L1 PWR and L2
PWR the OFF position since we will not be using the L1 or L2 XLR inputs for
a single mic, extending battery life. Remember, you will need to turn L1
PWR or L2 PWR back to the the ON position when you choose to use those
channels in the future.
• MIC SNR AND MIC PLACEMENT: Low noise preamps are effective at
improving poor signal-to-noise of downstream components, like noisy
cameras and recorders. However, low-noise preamps can not improve
poor signal-to-noise in upstream components. This is to say, garbagein, garbage-out. You will need to use a microphone with decent
signal-to-noise characteristics. Additionally, the microphone needs to
be placed close to the person speaking (no more than a foot and a
half away) for capture of high quality dialogue.
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• CONNECT BALANCED MIC: Connect a balanced XLR microphone into
the R XLR input. For simple dialog, set MIC/LINE to MIC and GAIN on HI for
the R channel. Apply Phantom Power to the R channel if necessary. See
the WARNINGS - Phantom Power section at the end of this document.
• UNBALANCED MIC: For minijack mics which are unbalanced, use a
Rode VXLR adapter to connect to the balanced XLR inputs of the
preamp. Note, if the miniplug pinout on your unbalanced mic is nonstandard, the Rode VXLR may short out the mic output and no signal
will make it to the preamp, so you will need to nd a different adapter
solution. Never apply phantom power to unbalanced mics, and see
the WARNINGS - Phantom Power section at the end of this document.
• SIGNAL ROUTING TO OUTPUT: Since this setup only uses one mic,
set MONO/STEREO to MONO. This will mix all of the mic inputs together,
and route them all to both the right and left outputs. If you wish to
have channel separation when you are using more than one mic, then
set to STEREO, and L1 and L2 will be routed to the left output channel,
and R will be routed to the right.
• CAMERA OVERLOAD PROTECTION: You may wish to use Audio Bracketing
for camera overload protection, indicated by the GREEN switch
settings. This mixes all of the microphones together (MONO setting),
and attenuates the right output by about 16dB (R OUT -16dB PAD set to
ON). So, if you blow out your main channel (left) you have a backup
recording on the right at a safe lower level that you can pull from in
post. This approach has advantages over other types of overload
protection, such as limiters. First, Audio Output Bracketing consumes
no power from the battery, and also adds no noise or distortion to your
audio. Second, every camera gain setting (and, every different camera)
will have a unique signal level at which clipping will start to occur. So, if
you were to attempt to use a limiter approach, you would need to recalibrate the point at which the limiter would kick in for each different
gain setting of the camera (and, each different camera).
• CAMERA SETTING FOR SIGNAL-TO-NOISE: The BMCC rmware remains a
work in progress. Please make sure you are subscribed to the juicedLink
blog. Here is our latest blog post related to BMCC camera settings.
• SIGNAL LEVEL ADJUSTMENT / METERING: Adjust the front panel
potentiometer volume control for XLR-L so the audio peaks splash up to
-12dB on the meter of the camera.
• HEADPHONES: Plug headphones the camera’s headphone output.
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• Explanation of Switches
o ENC GND: The NORM position connects analog ground to the
enclosure. The LIFT position disconnects the enclosure from analog
ground. See the “Mounting, Grounding, Ground Loops, and the
ENC GND Switch” section below for more details.
o Balanced GND Out: The NORM position connects analog ground
to the minijack output cable shield ground. The LIFT position breaks
that connection. See the “Mounting, Grounding, Ground Loops,
and Ground Switches” section below for more details.
o MIC/LINE: LINE inserts a 40dB pad at the XLR input before the
preamp circuit.
o GAIN - HI/LO: The preamp is typically used in the HI gain
position. LO gain is used when in a high signal level environment,
like a rock concert or the tarmac of an airport.
o PHANTOM - OFF/12V/48V: This controls the switching power supply
of the phantom voltage generating circuit.
o PHANTOM - XX > ON: The ON position routes the voltage from
the phantom voltage generating circuit to the corresponding XX
XLR input. See the WARNINGS - Phantom Power section of this
document.
o L1 PWR and L2 PWR - ON/OFF: Powers on/off the preamps for
the L2 and R XLR inputs.
o STEREO/MONO: MONO mixes all XLR inputs together, and presents
them all to both the right and left outputs. STEREO routes XLR-R to
the right output, and XLR-L1 and XLR-L2 to the left output.
o R OUT -16dB PAD - ON/OFF: This engages an approximately 16dB
attenuator in the right output channel. It is used in conjunction with
the MONO setting (the GREEN switch settings) to achieve Audio
Output Bracketing for camera overload protection.
o LiPoly/ALK: ALK sets the low battery threshold suitable for alkaline
batteries. LiPoly sets the low battery threshold suitable for LithiumPolymer batteries.
• Mounting the Preamp
o Mounting, Grounding, Ground Loops, and the Ground Switches
Ground Loops can result in a hum/buzz in your audio,
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and are created when multiple ground paths between
pieces of equipment exist. You will always have one ground
connection between the preamp and your camera, and
that is via the shield in the stereo minijack cable that goes
from the MIC OUT of the preamp into the MIC IN of the
camera. However, depending on how/where you mount
the preamp, a second ground connection can be created
between the preamp enclosure and camera enclosure.
The preamp enclosure is black anodized, which is non
conductive. So, any elements in contact with the black
anodized portion of the enclosure are not in contact
with the enclosure ground
Any silver parts of the enclosure, such as the female
1/4-20 tripod mounting hole, are electrically connected
to the enclosure. So, any components in contact with
these elements are also in contact with the enclosure
ground.
The camera mounting screw that goes through the
preamp is suspended by nylon shoulder washers, so it is
not in contact with the enclosure ground
In the NORM position of the ENC GND switch, the enclosure
ground is connected to the ground of the circuitry inside the
preamp.
So, if the camera enclosure nds a path to the preamp
enclosure, you will have a ground loop.
The NORM switch position is what is typically used when
the preamp is mounted to the bottom of the camera,
and there is only one ground connection between
the preamp and the camera via the shield of the
stereo minijack cable. There is no ground connection
between the enclosure of the preamp to the enclosure
of the camera, since the camera mounting screw
that goes through the preamp and is in contact with
enclosure of the camera, but the camera mounting
screw that goes through the preamp is electrically
isolated from the preamp enclosure via the nylon
shoulder washers.
In the LIFT position of the ENC GND switch, the circuitry
inside the preamp is electrically isolated from the ground
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of the enclosure.
So, if the camera enclosure nds a path to the preamp
enclosure, you will LIFT the ground to the preamp
enclosure to eliminate the ground loop. A potential
path could be where your camera is mounted to a rig,
and the preamp is mounted to the same rig via the
silver female 1/4-20 tripod mounting hole on the bottom
of the preamp.
However, if you LIFT the enclosure ground from the
circuitry of the preamp when there is no ground
connection between the camera enclosure and
the preamp enclosure, then you will be disabling
phantom power. This is because the XLR connector
pulls its ground from the preamp enclosure, so the
XLR connector needs to get the ground reference
from the enclosure of the camera when in the LIFT
position. Additionally, if you disconnect the stereo
minijack cable between the MIC OUT of the preamp to
the MIC IN of the camera, you will also be disabling the
phantom when in the LIFT position.
o Mounting to the top of your BMCC
This process is best communicated visually. Please see the
“Mounting Directly to Top of BMCC” video, above.
• Audio Connection Between Preamp and Camera
o Please see the “Cabling to BMCC Audio Inputs” video, above.
• Powering
o A 9V battery must be placed in the battery tray in accordance with
the polarity markings found at the bottom of the battery tray.
o Different battery chemistries will have different drop out
voltages. The low battery threshold indicator is calibrated for both
alkaline and lithium-polymer (rechargable) batteries. Select the
appropriate switch setting for ALK/LiPoly for the battery type used.
o Preamps are high-current devices, unlike other things like smoke
detectors, etc. So, they require that the batteries used are
fresh. Please note that it is possible to get bad packs of batteries
from the store. Weakened batteries have a buildup of their
internal resistance. The larger this resistance becomes, the more
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of a voltage drop that will occur when supplying large currents, thus
triggering the low battery indicator.
o Maximizing power efciency:
Phantom power sucks a lot of current from the
battery. Whenever it is not needed, make sure that phantom
power is off. Whenever you have the option to run a mic from
its own battery or phantom power, run it from its own battery
and keep phantom power off (or, do not route phantom
power to that mic, if you are required to have phantom
power on to power another mic that is connected). It is often
desirable to use a mic that works from phantom power only,
since that mic can be much smaller and lighter without the
battery compartment. When you are in the market for a new
mic, many modern mics will work down to 12V phantom, so
consider one of those mics. It consumes much less power to
run from 12V instead of 48V.
The preamp has the ability to power down unused XLR
inputs, via the L1 PWR and L2 PWR switch. Power off when
those inputs are not in use, and this will extend battery life
considerably.
• Connecting to the Preamp Inputs
o The preamp inputs are balanced XLR, where pin-2 is HOT, pin-3
is COLD, and pin-1 is GND. So, balanced XLR microphones will
directly interface using the MIC setting. The output of balanced
mixers will interface directly as well, and you may need to engage
the 40dB attenuator at the input by using the LINE setting.
o Unbalanced sources (minijack mics, wireless mics) can interface to
balanced inputs. You will need to use a connector that connects
pin-3 COLD to pin-1 GND. For example, the Rode VXLR connector
provides such functionality going from minijack to XLR. Never apply
phantom power to unbalanced sources. See the WARNINGS -
Phantom Power section at the end of this document. Note, the
VXLR will not work with mics which have a miniplug with a nonstandard pinout.
o Phantom Power
Condenser-type microphones require power. Some
microphones can be powered by their own internal
battery. Other microphones require power to be sourced
by the equipment that the mic is being plugged into, and
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transmitted up the mic cable from the mixer to the mic. This is
known as phantom power.
PHANTOM - OFF/12V/48V: This controls the switching
power supply of the phantom voltage generating
circuit. Check your microphone user manual for its powering
requirements. Select the lowest phantom setting that is
required by all mics being used.
PHANTOM - XX > ON: The ON position routes the voltage from
the phantom voltage generating circuit to the corresponding
XX XLR input.
IMPORTANT. See the WARNINGS - Phantom Power section at
the end of this document.
Phantom power sucks a lot of current from the
battery. Whenever it is not needed, make sure that phantom
power is off. Whenever you have the option to run a mic from
its own battery or phantom power, run it from its own battery
and keep phantom power off (or, do not route phantom
power to that mic, if you are required to have phantom
power on to power another mic that is connected). It is often
desirable to use a mic that works from phantom power only,
since that mic can be much smaller and lighter without the
battery compartment. When you are in the market for a new
mic, many modern mics will work down to 12V phantom, so
consider one of those mics. It consumes much less power to
run from 12V instead of 48V.
• Signal Level Controls for each XLR Channel
o Signal level control is accomplished via MIC/
LINE switch, GAIN switch, and volume control potentiometer (on
the front panel. For typical use with a microphone recording simple
dialogue, you will have MIC/LINE set to MIC, GAIN set to HI, and you
will adjust the volume control potentiometer so the peaks splash just
splash up to the -12dB on the meter of the camera.
o The LO GAIN setting is used for very high signal level environments,
like a rock concert or the tarmac of an airport, to provide more
headroom in the preamp.
• Routing Preamp Intputs to Camera
o MONO mixes all XLR inputs together, and presents them all to
both the right and left outputs. STEREO routes XLR-R to the right
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output, and XLR-L1 and XLR-L2 to the left output.
• Meter Calibration
o See the “Read this rst” section at the top.
• Achieving the Best Signal-to-Noise
o The BMCC rmware is still a work in progress. Please see make
sure you subscribe to the juicedLink blog. Please see our blog
post regarding how to work with the current version of the BMCC
rmware.
o Turn down the potentiometer volume controls all of the way for any
unused XLR input.
o Limitations in Signal-to-Noise: Low noise preamps are effective at
improving poor signal-to-noise of downstream components, like
noisy cameras and recorders. However, low-noise preamps can not
improve poor signal-to-noise in upstream components. This is to say,
garbage-in, garbage-out. You will need to use a microphone with
decent signal-to-noise characteristics. Additionally, the microphone
needs to be placed close to the person speaking (no more than a
foot and a half away) for capture of high quality dialogue.
• Achieving the Widest Dynamic Range
o Audio Output Bracketing
You may wish to use Audio Bracketing for camera overload
protection, indicated by the GREEN switch settings. This mixes
all of the microphones together (MONO), and attenuates
the right output by about 16dB (R OUT -16dB PAD - ON). So,
if you blow out your main channel (left) you have a backup
recording on the right at a safe lower level that you can pull
from in post.
This can be used with any camera. You can change gain
settings in the camera with no problem. You can even
combine it with the camera’s AUTO setting for even further
extended dynamic range
This approach has advantages over other types of overload
protection, such as limiters in preamps. First, Audio Output
Bracketing consumes no power from the battery, and also
adds no noise or distortion to your audio. Second, every
camera gain setting (and, every different camera) will
have a unique signal level at which clipping will start to
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occur. So, if you were to attempt to use a limiter approach,
you would need to re-calibrate the point at which the limiter
would kick in for each different gain setting of the camera
(and, each different camera).
• WARNINGS:
o Phantom Power: NEVER apply phantom power to anything other
than a mic which requires it, otherwise you are basically shorting
48V to ground and risk damaging your equipment. Check your
microphone user manual for its requirements. When the phantom
power gets shorted, it sucks a huge amount of current from the
battery (so, your battery life will be awful). Plus, the phantom power
IC will get extremely hot. After a period of time, it may not be
able to handle it and burn out. Plus, whatever you are applying
phantom power to can get damaged (such as mixers and ribbon
mics). Never apply phantom power to: 1) wireless mic receivers,
2) any unbalanced mic, 3) ribbon mics, 4) dynamic mics, 5) mixers,
6) condenser mics already being powered by their own internal
battery.
o Risk of Hearing Loss: During production, you will be using
headphones for monitoring audio. Headphone ampliers
are capable of driving signal levels which are damaging to
hearing. Protect your hearing. Start with the volume at a low
level, and use at the lowest practical signal level. Don’t wear
headphones when plugging headphones into headphone amps,
when powering on/off your equipment, when plugging external
equipment into your mixer (mics, mixers), when powering on
phantom power.
o Risk of Electric Shock: The enclosure is electrically conductive and
electrically connected to the shields of the mic cables plugged into
the mixer. Avoid electrocution and observe caution with cable runs
in areas where high voltages and/or currents exist.
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