Setting Input Trim Levels; Peak Led Method - Alesis MULTIMIX 12R Reference Manual

Operating Instructions

Setting input trim levels

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Proper setting of the [TRIM] controls is crucial to low-noise, distortion-
free operation. If the trim is set too high, there will be distortion even
if the channel faders are low. If the trim is set too low and the channel
faders are raised to get the signal loud enough, you will be amplifying
the noise of the mixer.
Instead of doing this, get as much gain as possible as close to the signal
source as possible. If you've plugged a synthesizer or other line-level
source into the Multimix 12R, set its output volume to maximum. If a
microphone is the source, the Multimix 12R's [TRIM] control will
determine the gain of the system.
✪
The goal is to get the signal as loud as possible as early as possible
in the signal path, without causing clipping (distortion) anywhere in
the path or in the sound system.

PEAK LED method

Each channel of the Multimix 12R has its own [PEAK] indicator, which
will light when the signal level rises to within 6 dB of clipping. In
situations where the maximum signal-to-noise ratio is required (such
as digital recording), use the PEAK LED as a guide for setting the
[TRIM] control.
✪
When the PEAK LED is flashing, it does NOT necessarily mean that
distortion has occurred. There is usually some headroom left if the PEAK
LED is flashing momentarily on the loudest peaks.
1. With the sound source active, and the channel fader down to
minimum, raise the [TRIM] control until the PEAK LED flashes
occasionally on the loudest transients.
2. If desired, lower the [TRIM] control slightly until the flashing stops.
Note for extremely high level line inputs in stereo channels: If the
[TRIM] setting is set below unity (12 o'clock position) on a stereo
channel, it is possible for the first input stage to clip without the
PEAK LED coming on. If distortion is still heard after lowering the
trim to its minimum setting, it means the source is extremely high
(+22 dBu or higher). In this case you must lower the output level of
the source, use an external pad, or repatch to a LINE IN on
channels 1-8 (which can take up to +32 dBu levels before clipping).