Operation Precautions; Input Attenuators; Powering Up - Soft Start; Indicators - Martin Audio MA4.2s User Manual

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CONTENTS
Never connect either output terminal to ground or to some other output or input terminal (see warnings in
chapter 1)
For normal two-channel operation, connect each speaker load across the output's positive and negative terminals.
Pay attention to speaker polarity; loudspeakers connected out of polarity degrade sound quality.
Keep the loudspeaker cables as short as possible and use a good quality stranded cable. Do not use shielded wire,
such as microphone or guitar cable. The loudspeaker cable reduces the power of the amplifiers in two ways:
It increases the load impedance and introduces resistive power losses.
8 OPERATION
8.1

Operation precautions

8.2 Powering up – Soft start
W he n yo u p ow e r up th e am p lifier it ta ke s a cou ple o f se con ds to che ck its circu its. T his is kn ow n a s th e "so ft-start" or
"slow -start" se qu en ce. T h e fa ns th en blow a t h ig h spe ed be fo re go in g into "id le " a nd th e tw o b ottom g re e n LE D 's
illum in a te to sho w the a m plifie r is o pe ra tio na l.
8.3

Input attenuators

T he two in pu t level atte n ua to rs on th e fron t p an e l ad ju st th e sig na l leve l fo r the ir re sp ective a mp lifie r ch a nn el in a ll
m od es. T he y a re calibrate d in d B to h elp th e settin g up of a ctive lo ud sp e aker system s.
In brid g ed m o de , bo th co n trols m ust b e in th e sa m e po sitio n, so tha t the sp ea ke r loa d w ill b e sh a re d eq u ally be tw ee n
the cha n ne ls.
8.4

Indicators

The two-bottom green "ON" LED's indicate that the output circuits are receiving the correct rail voltage.
The "-40 dB" LED's illuminate if the output signal is greater than - 40dB (with 0dB as reference to full output power).
These LED's also act as signal present indicators.
All material © 2007. Martin Audio Ltd. Subject to change without notice.
PRINT
WARNING: To prevent electric shock, do not operate the amplifier with any of the loudspeaker
cable conductors exposed.
Make sure that the power switch is set to "OFF" before connecting any input or output or operating the
switches on rear panel. See pages
Make sure that the AC mains voltage is correct and the same as the one printed on the rear panel of the
amplifier. See pages 10, about operating voltage and power consumption.
Make sure that the operating mode switches on the rear panel for, gain, clip limiting, and MLS selection
are in the correct position. See page
selection.
It is always a good idea to turn down the gain controls during power-up, to prevent loudspeaker damage in
due to a high signal being present at the input.
Martin Audio – MA4.2s Amplifier
10 about installation.
7 " operating modes", page 15
14
8
"clip limiters" and page for MLS
GUIDES