Sound Devices 442, User Manual And Technical Information, Page: 11 / 34

9
Phantom Power
Phantom powering is a fi xed DC voltage between 12 and 48 volts. This voltage is resistively applied to pin-2
and pin-3 of an XLR connector relative to pin-1. There is no voltage difference between the signal pins-2 and -3.
Dynamic microphones will operate as normal when phantom power is applied to them.
The 442 can provide up to 10 mA to each input at 48 V, suffi cient for the most power-hungry condenser
microphones. Many phantom powered microphones do not require 48 V and can be properly powered with 12
V. When acceptable, use 12 V phantom to extend the 442’s battery life. The phantom voltage level can be set to
either 12 V or 48 V and is applied across all inputs where phantom power is selected.
T-Powering
T-powering is a microphone powering scheme used by several European condenser microphone manufacturers.
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. The 442
provides positive T-power on the three-pin XLR connector, pin-2 has +12 volts relative to pin-3. T-power can be
selected for each input.
When using “red dot” T-powered microphones (reverse polarity T-power) use a polarity-reversing adapter on
the input, otherwise damage to the microphone may occur.
Phantom and T-powering are not interchangeable. Use T-powering only for T-powered microphones.
High-Pass Filters
5
Each channel of the 442 has an adjustable high-pass fi lter. High-pass (or low-cut / low roll-off) fi lters
are useful for removing excess low frequency energy from audio signals. Wind noise is a common unwanted
low frequency signal that can be reduced with the use of a high-pass fi lter. For most audio applications
engaging the high-pass fi lter is benefi cial, because audio information below 100 Hz is rarely used, especially for
speech reproduction.
The 442's high-pass fi lter circuit features an adjustable corner (–3 dB) frequency over a range from 80-240 Hz.
Below 80 Hz, the fi lter's slope is 12 dB/octave. At higher corner frequency settings, the slope is 6 dB/octave.
See
Specifi cations The purpose for this compound slope is to give additional roll-off at the 80 Hz setting to reduce
wind noise and low frequency rumble. The higher settings can be used to counteract the proximity effect of
directional microphones where a more gentle slope is desired.
The 442's high-pass fi lter circuit is unique because of its placement before any electronic amplifi cation. Most
mixer's high-pass fi lter circuits are placed after the microphone preamplifi er, where all of the high-energy
low-frequency signals get amplifi ed. By virtue of the 442's circuit cutting the low-frequency signals before
amplifying, higher headroom is achieved in presence of signals with a lot of low-frequency energy.
When possible, attempt to equalize at the sound source with microphone selection, placement, windscreens, and
onboard microphone fi ltering. Many microphones have on-board high pass fi lters, and the high-pass fi lters on
the 442 can be used in conjunction with the microphone's fi lter to increase the fi lter's slope.
The fi lter can be removed from the circuit completely by moving the high-pass fi lter control to the full counter-
clockwise (detented) position. The high-pass fi lter potentiometer can be adjusted easily and then recessed to
hide it from the mixing surface.