Alesis 4 Reference Manual page 22

Connections – Chapter 2
Mono In - Stereo Out. If you only want to feed the MidiVerb 4 a mono input, but
wish to connect both of its outputs back to the mixer, you will need three 1/4" audio
cables. Connect a mono cord from an effect send to the [LEFT/CH.1] input of the
MidiVerb 4, another mono cord from the [LEFT/CH.1] output of the MidiVerb 4 to an
effect return or other mixer input, and another mono cord from the [RIGHT/CH.2]
output of the MidiVerb 4 to an adjacent effect return or mixer input.
Stereo In - Stereo Out. This connection is similar to the one described above.
However, by utilizing two sends from the mixer, we add one more cord and can now
send a stereo signal to the MidiVerb 4's inputs. Example, if you connected sends 3
and 4 to the [LEFT/CH.1] and [RIGHT/CH.2] inputs, and had a stereo instrument
(such as a keyboard) connected to two channel inputs of the mixer (either one
panned hard left and hard right), you would send the left channel to send 3 and the
right channel to send 4.
Dual Mono. Alternatively, you could have two discrete effect sends between the Left and
Right channel, and process them separately within the MidiVerb 4 by using one of the
Dual Mono Configurations (see chapter 3). Again, using 2 aux sends from the mixer,
connect two mono cords to the [LEFT/CH.1] and [RIGHT/CH.2] inputs of the MidiVerb 4,
and connect two other mono cords from the [LEFT/CH.1] and [RIGHT/CH.2] outputs of
the MidiVerb 4 to two mixer inputs. This hookup allows discrete processing of the two
channels, since separate effects are dedicated to each channel.
MidiVerb 4 Reference Manual 21