Aphex 1788A Premium Eight Chan Mic Pre - Manual (Page 17)

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MICROPHONE PREAMPLIFIER
Page 17
Instruction Manual
4. FUNCTIONS IN DETAIL
channels is muted. The channel or channels that have been muted will flash double dash
marks in the Gain display of the individual channel status readout to indicate their muted
status. The flashing dash marks will alternate with the current gain setting. All parameters
may be adjusted while a channel is muted. When receiving gain settings (input or output)
remotely, the MUTE readout indication in the channel status readout will be overwritten
on any muted channel. To re-display the MUTE function, the GAIN SELECT button or the
CHANNEL SELECT button must be pressed again. The MUTE function does not affect the
headphone monitor output or the digital outputs.
Polarity Reverse
The POLARITY REVERSE button reverses the microphone preamp’s output polarity.
This can be a very useful feature in tracking down polarity differences in microphones
and/or cables. It is much easier and quicker than the alternative of swapping cables
and equipment. When the POLARITY REVERSE is inserted into a selected channel, the
corresponding POL REV LED indicator will illuminate on that channel’s status readout.
Additionally, the POLARITY REVERSE button itself will be illuminated.
Refer to Section 5.6 for instructions on how to properly use the POLARITY REVERSE
function.
Low Cut 75Hz
To help reduce low frequency rumble that can be caused by wind, handling of the
microphone or bad vocal articulation (popping “P’s”), a 75 Hz, 12dB per octave low cut
filter is provided. In general, this filter could be engaged when mic’ing vocals as it will
not usually affect the tonality of the human voice. When mic’ing instruments with very
wide bandwidth in the low frequency range, you may want to defeat the filter unless
there is substantial extraneous low frequency noise. When the LOW CUT 75Hz filter is
inserted into a selected channel, the corresponding LOW CUT LED indicator will illuminate
on that channel’s status readout. Additionally, the LOW CUT 75Hz button itself will be
illuminated.
26dB PAD
Using the 26dB PAD attenuates the preamp’s input signal by 26dB. It allows the channel
to receive line level inputs from a wireless microphone receiver or other high level device.
When the 26dB PAD is inserted into a selected channel, the corresponding PAD LED
indicator will illuminate on that channel’s status readout. Additionally, the 26dB PAD
button will be illuminated.
PHANTOM +48V
Pressing the PHANTOM +48V button engages the internal phantom power source. The
48 volt microphone power ramps up and down very slowly to avoid glitches. The ramping
also protects powered microphones from current surges, which have been known to
cause microphone damage. When the PHANTOM +48V power source is used on a
selected channel, its corresponding +48V LED lights up on the channel’s status readout.
Additionally, the PHANTOM +48V button itself will be illuminated.
CAUTION: Hot-plugging a microphone into a phantom powered input causes a very loud
impulse which can cause speaker damage. To be safe, allow at least 20 seconds for the
phantom power to discharge before plugging or unplugging a microphone.