Meyer Sound Laboratories, Inc.
2832 San Pablo Avenue
Berkeley, CA 94702
Operating Instructions
M-1A
Control
Electronics
Unit
The Meyer Sound M-1A is
an active signal processor
designed for use with Meyer
Sound UPA-1C and UM-1C
loudspeakers. lt is a single
channel device, and it
occupies a single 1
3
⁄
4
-inch
rack space. The functions
of the M-1A are:
■
Active crossover for bi-
amplification
■
Loudspeaker frequency
response and phase
response alignment
■
SpeakerSense™ driver
protection
+
–
Input
Sub
In
Lo
Hi
Sense
Lo
Out
Hi
Out
1/4 A
Hi Channel
+
–
Lo Channel
Amplifier
Loudspeaker Cable
Input
1 Meter
Pigtail
Adapter
Red
Sense
Cable
Red
Black
Sense
Cable
Black
Connections
The M-1A operates at line level and is de-
signed to be the last component in the chain
before the power amplifier. Connections to
the M-1A should be made according to the
diagram above.
1.
Signal inputs
to the M-1A may be either
balanced or unbalanced. For best sig-
nal-to-noise ratio, the average input level
should be at least 1 volt RMS. The M-1A
will accept peak inputs of up to +26 dBv
balanced, or +20 dBv unbalanced.
2. The
Sub input
is used only when the M-
1A is operated in conjunction with Meyer
Sound B-2, B-2A or B-2AEX subwoofer
Controllers.
3.
SpeakerSense™
connections are made
from the output of the power amplifier
back to the M-1A Sense inputs. The Hi
output of the power amplifier must be
connected to the Hi Sense input, and the
Lo output of the power amplifier to the Lo
Sense input in order for the SpeakerSense
driver protection circuitry to operate prop-
erly.
Note.
Polarity of these connections does not
matter.
4.
Signal outputs
from the M-1A may be
either balanced or unbalanced. The max-
imum output levels before clipping are
+26 dBv balanced, +20 dBv unbalanced.
5. Connections between the power amplifier
outputs and the Meyer Sound loudspeaker
used with the M-1A should be made ac-
cording to the instructions for the particular
loudspeaker (UPA-1C or UM-1C). These
connections
must be verified for correct
polarity
, and correct channel assignment
(Hi to Hi, Lo to Lo). Color codes given
in the diagram are those used for Meyer
Sound cables and adapters.
Note.
The grounding strap on the M-1A rear
panel connects circuit ground (signal com-
mon) to earth ground (U-ground). Lifting this
strap from the terminal block disconnects
circuit ground from earth ground (the chas-
sis remains connected to U-ground). If hum
problems occur, this feature may be used to
control ground loops in the system.
