Alesis MultiMix12Firewire Frequently Asked Questions Manual page 11

So, the reverb gets returned not to the individual channels (which would be
impossible) but rather to the MAIN mix. (The amount of the effect that gets
returned to the MAIN mix is determined by the AUX RETURN knobs.)
Therefore, if you want to record these effects, record the MAIN mix, rather than
the individual channels.
By the way, there's nothing unusual about all this: practically all mixers work the
same way.
I've heard that some audio equipment operates better if it is left on all the
time. Should I always keep my MultiMix on?
We advise against leaving the MultiMix on all the time. Some tube-based gear
does sound noticeably different after a couple of hours of warm up, but solid-state
devices such as the MultiMix generally achieve optimum performance very
quickly after power-up.
Why is the left input of my stereo line-in channel is being sent to both the left
and right channels in my audio application?
This is an artifact of the way that the MultiMix routes the line-level input signals:
If only the left jack of a stereo line pair is used, that signal is routed
equally to the left and right sides of the stereo channel.
If only the right jack of a stereo line pair is used, that signal is routed to
the right side of the stereo channel, and the left side is left silent.
If both jacks of a stereo line pair are used, the left jack is sent to the left
side, and the right jack is sent to the right side.
Therefore, if you are only using one input in a stereo pair, record just that one
channel and not the one adjacent to it.
I would like to route audio from the computer to the MultiMix, apply the
MultiMix's EQ and digital effects, and then record this audio back to the
computer. Is that possible?
This is possible, but it requires some additional cabling.
1. Turn the HEADPHONE/CONTROL ROOM volume knob all the way
down.
MultiMix Firewire FAQ & Troubleshooting Guide Page 11