JLCooper MLA-1 User Manual

MLA-1 / MLA-10

Installation/Operations Manual

Table of Contents

Introduction 1

MLA-1 vs. MLA-10 Comparison 3

MLA-10 Details 4

MLA-1 Details 6

Special Interest Notes 8

1

MLA-1 / MLA-10

Installation/Operations Manual

INTRODUCTION

This is the preliminary manual covering the installation and operation of the MLA­1 and MLA-10 MIDI Line Amplifiers.

The MLA-1 and MLA-10 are designed to act as long distance "amplifiers" for
MIDI signals. The normal MIDI protocol calls for a maximum cable distance of
about 50 feet, clearly not sufficient for many installations. The reason for this
restriction has to do with the basic type of electrical protocol (current loop), which
lends itself to inexpensive implementation.

Successful installations of 100 feet or so have been made, but require good (low
capacitance) cable. Much more than 100 feet of MIDI transmission requires
some sort of amplification.

The MLA-1 and MLA-10 take a MIDI input and convert it to a "push/pull" signal,
much like RS-422. This low impedance type of signal lends itself to long distance,
high reliability installations required by professional applications.

Since the MIDI signal is converted into a different format, an installation requires
a transmitter on one side of the long run, and a receiver on the other. Both the
MLA-1 and MLA-10 have 4 transmitters and 4 receivers each.

It is important to note that an installation requires either an MLA-1 or MLA­10 on each side of the long run. Even a single MIDI signal requires this
pairing.

Normally, the long run consists of a multi-conductor cable. A twisted pair is
needed for each MIDI signal. The MLA-10 can provide power to the MLA-1; in
that case an additional number of wires is needed. For instance, a 4 input /
4 output system would need 8 twisted pair (16 conductors) for the signals, and
possibly another 4 conductor for power, for a total of 20 conductors.

The choice between the MLA-1 and MLA-10 depends on mounting and powering
requirements: the MLA-10 is a rack mountable unit with built-in MIDI connectors,
while the MLA-1 is normally meant to be mounted in a wall box where the actual
MIDI connectors are provided on a wall plate. The MLA-1 can receive its power
thru the multi-conductor long cable from a MLA-10 if desired.

As such, the MLA-1 and MLA-10 units are identical in concept, but slightly
different in implementation. We will treat each separately in this manual to
(hopefully) avoid confusion.

2

MLA-1 / MLA-10

Installation/Operations Manual

MLA-10

• The MLA-10 is designed as a

rack-mountable unit. It occupies a
single height of rack and is less than
4 inches deep.

• The MLA-10 is powered by a

UL-approved wall transformer and
has a front panel power switch and
power indicator.

• This unit has eight front panel

LEDs that indicate MIDI activity on
each of the 4 MIDI inputs and 4 MIDI
outputs.

• On the rear panel are 4 MIDI

input DIN connectors and 4 MIDI
output DIN connectors.

• On the rear panel is a 24-

position wire terminal strip for
connection of the multi-pair long
cable. This is a plug-in type, so that
the unit may be removed without
disconnection of individual wires.

MLA-1

• The MLA-1 is designed as a

surface mountable unit. This may be
inside of a wall box. It measures 6.7"
by 6.2" by .8".

• The MLA-1 is normally

powered remotely from a MLA-10,
but may be ordered from the factory
for wall-transformer power.

• Since this unit is normally

mounted inside a wall box, no LEDs
are included.

• MIDI connection is made via a

24 position terminal strip. Normally,
the installer would mount the MIDI
DIN connectors on a wall plate, and
wire these to the terminal strip.

• The unit has another 24-

position wire terminal strip for
connection of the multi-conductor
long cable.

3