Pro Tools | PRE Guide8
Input Impedance (Represented as Z)
The Input Z switch sets the input impedance for a
PRE channel to 1.5 k,15k, or 1.5 M.
The three Input Z LEDs indicate the current set-
ting:
1.5K
Typically used for microphone inputs, this is
the default setting when Source is set for Mic.
15K
Typically used for line level inputs, this is the
default setting when Source is set for Line.
1.5M
Typically used for instrument inputs, this is
the default setting when Source is set for Inst.
To change input impedance, do one of the
following:
If the input Source is Mic, press Input Z once to
change to the next setting, or multiple times to
toggle through the three settings.
If the input Source is Line, press Input Z to
change to 1.5K or 15K.
If the input Source is Inst (instrument), the Input
Z cannot be changed from its default 1.5M set-
ting.
Channel Status Section
Each PRE channel provides switched control for
48V (phantom power), phase reverse, input pad,
access to a unity gain insert send/return, and a
high-pass filter. In addition, all eight channels have
individual Mute switches and signal status LEDs.
Signal Present/Clip (SIG) LEDs
These LEDs indicate the status of a channel’s input
signal. Green indicates signal is present (–45 dB)
and red indicates clipping. When there is no signal
present or the signal is below –45 dB, the LED is
off.
When clipping occurs, the LED remains lit or
clears, depending on the Peak Hold setting. Clips
can also be manually cleared with the Clear Clip
switch.
48V Switch and LEDs
This switch applies 48V phantom power to the Mic
Inputs. When lit (red), these LEDs indicate which
channels have 48V enabled.
Mic Inputs can provide 48V phantom power for
microphones that require it to operate. If Source is
set to Line or Inst, phantom power automatically
disengages to avoid sending phantom power back
to the line level device through the XLR cable,
eliminating unnecessary power draw when not in
use for powering microphones.
Dynamic microphones (like a Shure SM57) do not
require phantom power to operate, but are not
harmed by it. Most condenser microphones (like
an AKG C414) do require phantom power to oper-
ate. If you are not sure about the phantom power
requirements for your microphone, refer to your
microphone’s documentation.
Although phantom power can be used safely
with most microphones, ribbon microphones
can be damaged by it. Always turn off phan-
tom power, and wait for the red 48V indica-
tor light to go completely off and any signal
to dissipate before connecting or disconnect-
ing a ribbon microphone.
Condenser microphones requiring phantom
power should not be “hot-plugged” into a
PRE Mic Input where phantom power is
active before plugging the microphone in.
This could potentially cause damage to PRE,
as well as to un-muted monitoring systems,
due to a loud “click” or “pop.”
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