302 Compact Production Mixer
User Guide and Technical Information
page 7
runtime. Many microphones do not require 48 V phan-
tom and can be properly powered from 12 V phantom
power. The phantom voltage level is globally selected
for all inputs - either 12 V or 48 V.
Microphones draw differing amounts of current based
on their design. Many phantom-powered mics will
operate at 12 V with no difference in performance as
compared to operating off of 48 V. As the mics draw
the same current no matter what the phantom voltage,
operating at 48 V consumes four times the power as 12
V with no performance gain! This excess power draw
can make a significant difference in battery life and is
the reason the 302 allows the user to select the phan-
tom voltage.
It is generally good practice to turn off phantom power
when not using a phantom powered mic, as phantom
power can capacitively couple noise into the mic inputs
with poor mic cables. Also, turn phantom power off
when using ribbon microphones since an improperly
wired cable can permanently damage the microphone.
The DYN (dynamic) position applies no voltage to the
microphone input.
The 12 V / 48 V phantom voltage switch sets the overall
phantom voltage selection. It does not apply this volt-
age to an input, only sets the phantom voltage avail-
able.
T-Powering
T-powering is a microphone powering scheme used by
several European condenser microphone manufactur-
ers. Today, T-powered microphones are not as common
as phantom powered microphones, but many are still in
regular use. Unlike phantom power, T-power resistively
applies 12 V between the signal pins -2 and -3. T-power
can be selected for each input. The 302 provides positive
T-power, where pin-2 on the XLR-3 connector has +12
volts relative to pin-3. When using “red dot” T-powered
microphones (reverse polarity T-power) use a polar-
ity-reversing adapter on the input, otherwise damage
to the microphone may occur. Do not apply phantom
power to T-powered microphones.
NOTE: Phantom and T-powering are not interchange-
able. Use T-powering only for T-powered microphones.
High-Pass Filters
Each channel of the 302 has a two-position high-pass fil-
ter. High-pass (or low-cut / low roll-off) filters are useful
for removing excess low frequency energy in audio sig-
nals. Wind noise is a common unwanted low frequency
signal and a high-pass filter is effective for reducing
wind noise. For most audio applications engaging the
high-pass filter is beneficial, since little usable audio
information exists below 80 Hz, especially for speech
reproduction.
The 302’s high-pass filters features a 12 dB/octave slope
with either 80 Hz or 160 Hz corner (- 3 dB) frequen-
cies. The 160 Hz settings can be used when aggressive
filtering is required. The 302’s high-pass circuit is unique
because of its placement before any electronic amplifi-
cation. Most mixer’s high-pass circuits are placed after
the mic preamp, where all of the high-energy low-fre-
quency signals get amplified. Because the 302’s circuit
cuts low-frequency signals before amplifying, higher
headroom is achieved in presence of signals with a lot
of low-frequency energy.
Where possible, attempt to equalize at the sound
source with microphone selection, use of windscreens,
microphone placement, and on-board microphone
filtering. Many microphones have on-board high pass
filters, and the high-pass filters on the 302 can be used
in conjunction with the microphone’s filters to increase
the filter’s slope.
The high-pass filter can be removed by placing it in the
center position.
Pan Switches
The pan switches assign an input channel’s audio signal
to the outputs. Inputs can be sent to the left, right,
or both outputs equally. The 302 features excellent
“off-attenuation” of the channels in the left and right
positions.
Input Channel Limiters
The input channel limiters act solely as “safety” limiters,
and are enabled when the output limiters are enabled
via the “LIM” switch on the front panel. (See Setup
Menu to defeat Channel Limiters entirely.) In normal
operation with a properly set gain structure, the thresh-
old of the channel limiter will rarely be reached. If ex-
tremely high input signal levels are approached, such as
in high SPL environments or with misadjusted settings,
the channel limiter(s) will activate to prevent the input
channel from clipping. Without a channel limiter, “hot”
signals could overload the channel and cause distortion.
It is recommended that the channel limiters be used at
all times. Below the factory-set threshold (just below
clipping), the limiter has no effect on audio. There is no
user-adjustments to the channel limiter thresholds.
When input channels 1 & 2 are linked as a stereo pair,
their channel limiters also link to perform the same gain
reduction to both channels equally. Each channel has an
orange limiter LED which illuminates in proportion to
the amount of limiting. If the orange LED for a channel
comes on regularly, it is recommended to turn down the
Gain.
