User Manual

HARDWARE INSTALLATION
42
AUDIO CONNECTIONS
Here are a few things to keep in mind as you are
making audio connections to your MOTU
interface.
Mic inputs with preamps
Connect a microphone using a standard mic cable.
☛ Do not connect a +4 dBu (line level) signal to
the mic inputs without using the -20dB Pad. It is
recommended you connect line level signals to the
quarter-inch inputs instead.
Phantom power
If you are connecting a condenser microphone or
another device that requires phantom power,
engage the mic input’s corresponding front-panel
phantom power button.
Preamp gain
The 1248’s preamp provides 63 dB of gain. Use the
front panel detented trim knobs to adjust gain as
needed for each input. The LCD provides visual
feedback as you turn the trim knob. Preamp gain is
digitally controlled, so you can make fine-tuned
adjustments in 1dB increments. You can also adjust
preamp gain in the web app. See “Device tab” on
page 18.
-20 dB pad
Each mic input (XLR jack) is equipped with a
-20 dB pad switch, to accommodate input signals
that could overdrive the input.
Guitar inputs
The 1248 provides two dedicated guitar inputs on
its front panel. These inputs are specially designed
for guitar or bass instruments, with a high-
impedance load of 1 megaohm. Use the knob to
adjust input trim.
Mic/line/instrument combo inputs
The 8M provides XLR/TRS combo jacks that
accept an XLR mic plug or a quarter-inch plug
from a line level source or guitar. Each input
provides individual preamp gain, pad and 48V
phantom power. (Phantom power is supplied to the
XLR connector only.) Use these general guidelines
for the 48V phantom power, pad and gain settings
on these combo input jacks:
V-Limit™
Each 8M mic input is individually equipped with
V-Limit (page 18), which help prevent digital
clipping from overloaded input signals. For details,
see “8M mic/guitar input meters with V-Limit™
compressor” on page 57.
Soft Clip™
Additional or alternative protection can be applied
individually to 8M mic/guitar inputs by enabling
Soft Clip (page 18). When enabled, Soft Clip
engages just before clipping occurs and helps
further reduce perceptible distortion.
TRS quarter-inch analog inputs and outputs
Quarter-inch analog inputs and outputs are
balanced (TRS) connectors that can also accept an
unbalanced plug.
☛ Quarter-inch analog outputs are not
cross-coupled. Therefore, use a TRS plug with the
ring disconnected. Not floating the negative
terminal will short it to the sleeve ground and
cause distortion.
Input 48V Pad Gain
Condenser mic On As needed As needed
Dynamic mic Off As needed As needed
Guitar n/a n/a As needed
-10 dBV Line level via TRS n/a n/a As needed
-10 dBV Line level via XLR Off -20 dB +12dB
+4 dBu Line level (XLR
only)
Off -20 dB Zero