Meridian 557 User manual

Meridian 557 Stereo Power Amplifier
user guide

Preface
ii
Sales and service in the UK
Meridian Audio Ltd
Stonehill
Stukeley Meadows
Cambs
PE18 6ED
England
Tel [phone]
Fax [phone]
World Wide Web
http://www.meridian.co.uk
Sales and service in the USA
Meridian America Inc
3800 Camp Creek Parkway
Building 2400
Suite 112
Atlanta
GA 30331
Tel [phone]
Fax [phone]
Designed and
manufactured in the UK by
Digital Gramophone and Wireless Ltd
Stonehill
Stukeley Meadows
Cambs
PE18 6ED
England
Copyright © 1993–1996 Digital
Gramophone and Wireless Ltd
Part no: 557/1
This guide was produced by
Human-Computer Interface Ltd,
Cambridge, England.

iii
Preface
Contents
Introduction 1
Introduces the 557 Stereo Power
Amplifier, and provides an overview of the
other products available in the Meridian
500 Series.
The Meridian 500 Series ........................ 2
Sample configurations ........................... 3
Specification and accessories ............... 6
Setting up the Stereo
Power Amplifier 7
Describes how to unpack, install, and use
the Stereo Power Amplifier, and explains
what you should do if your Stereo Power
Amplifier requires servicing.
Unpacking .............................................. 8
Connecting the Stereo Power
Amplifier ................................................. 9
Troubleshooting ..................................... 14
Maintenance .......................................... 15
Service and guarantee ........................... 16
Index ...................................................... 17

Preface
iv

Introduction
In choosing the 557 Stereo Power Amplifier you have acquired a
component that combines major advances in audio and engineering
design.
The 557 Stereo Power Amplifier uses a unique feedback topology and
precision local error correction system. It includes a massive twin wound
toroidal transformer, and the unit has full thermal, load, and DC protection.
The 557 Stereo Power Amplifier can also be operated in bridge mode, for
over three times the power output to a single loudspeaker.
This guide is designed to enable you to obtain the best possible results
from the unit in conjunction with the other units in your system.

2
Introduction
The Meridian 500 Series
The Meridian 500 Series is a unique system of digital, analogue,
and video components designed to meet the demand for
absolute quality, ease of use, and lasting value.
The flexibility of the Meridian 500 Series is such that you can
assemble a system as simple or as complex as you need,
perfectly suited to your musical and environmental requirements,
and with the ability to add to it or change it at a later date should
your requirements change. The 500 Series is also compatible
with the existing Meridian 200 Series and 600 Series
components.
Each Meridian 500 Series component is housed in a matching
slim line case. Front panel controls provide access to the most
important functions, and the full range of functions is available
from the Meridian System Handset using a simple and intuitive
control interface.
500 Series communications
The Meridian 500 Series includes a sophisticated
communications link, to ensure that any configuration of units
will work together as a fully integrated system.
The 500 Series communications system allows you to control
any combination of units using a single handset, and ensures
that your commands from the handset are interpreted
unambiguously. It also allows all the units to be switched off
from the front panel of any unit in the system.
Professional features
The 500 Series also provides features for professional users,
including RS232 computer control, and balanced connections.
The following pages give examples of four suggested
configurations to illustrate the flexibility of the Meridian 500
Series.

Introduction
3
Sample configurations
500 Compact Disc Transport
504
500
562
DSP5000DSP5000
A500
504
508 502
557
A500
508 Compact Disc Player
The 508 Compact Disc Player is an integrated CD transport and
converter, providing both digital and analogue outputs.
The 508 Compact Disc Player is ideally suited for use with the
Meridian 557 Stereo Power Amplifier and A500 Loudspeakers,
with control over the volume and source selection provided by
the 502 Analogue Controller. These units provide balanced
inputs and outputs, allowing a completely balanced system to
be created.
The 500 Compact Disc Transport provides a precision digital
output, and can drive DSP5000 Digital Loudspeakers directly.
A 562 Digital Control Unit can be added to cater for conventional
analogue sources, and provide source selection between up to
12 different analogue or digital sources.
The 504 FM Tuner is an ideal addition to the system if radio
reception is required.

4
Introduction
566 20-bit Digital to Analogue
Converter
502 Analogue Controller
A500
566
500
557
A500
502
The digital output provided by the 500 Compact Disc Transport
can be decoded by the 566 20-bit Digital to Analogue converter
to provide a high-quality audio output for use with a
conventional audio preamplifier. The 566 20-bit Digital to
Analogue Converter can also decode digital signals from other
sources, including LaserDisc players and Digital Audio Tape.
The 502 Analogue Controller is a full function preamplifier for use
with any analogue source, and includes balanced inputs to allow
you to take advantage of balanced sources, including the 566
20-bit Digital to Analogue Converter. It provides balanced
outputs which are ideal for use with the 557 Stereo Power
Amplifier.

Introduction
5
562V Multimedia Controller
LaserDisc
Video recorder
500 562V
Television
504
Satellite
DSP6000 DSP6000
The 562V Multimedia Controller is the ideal control unit for use
with the Meridian DSP6000 Digital Loudspeakers.
It provides direct digital inputs for digital sources, such as the
500 Compact Disc Transport and LaserDisc sound, together
with precision Delta Sigma Analogue to Digital Conversion, for
conventional analogue sources such as the 504 FM Tuner and
video sound.
It also includes video switching for CVBS and S-VHS signals,
such as from a satellite receiver, LaserDisc player, or video
recorder.

6
Introduction
Specification and accessories
Specification
Input 1.4V RMS.
Output (stereo) Greater than 200W per channel into 8Ω.
Greater than 300W per channel into 4Ω.
Output (bridge) Greater than 390W into 16Ω.
Greater than 650W into 8Ω.
Greater than 950W into 4Ω.
Distortion Less than 0.05%.
Noise Less than -90dB.
Finish Black textured enamel and glass.
Heatsinks black painted aluminium.
Dimensions 176mm x 400mm x 320mm
(6.9" x 15.7" x 12.6").
Weight 27kg.
Consumption 30VA quiescent, 1200VA max.
Meridian Audio reserves the right to amend product
specifications at any time.
Available accessories
The following accessories are available from your dealer:
❍Power cord Europe.
❍Power cord Canada and USA.

Setting up the Stereo
Power Amplifier
This chapter explains how to install the Stereo Power Amplifier. It
describes what you should find when you unpack the Stereo Power
Amplifier, how you should connect it to your other audio equipment, and
the siting constraints.
You should not make any connections to the Stereo Power Amplifier or to
any other component in your system whilst the AC power supply is
connected and switched on.

Setting up the Stereo Power Amplifier
8
Unpacking
The 557 Stereo Power Amplifier comes in a box containing the
following components:
❍557 Stereo Power Amplifier.
❍1 power cord.
❍2 phono shorting plugs.
❍This manual.
You are advised to retain the packing in case you need to
transport the unit.
The 557 Power Amplifier weighs 27kg. Do not attempt to lift
it without assistance.
Before connecting power
Before you begin installation you should ensure that your Stereo
Power Amplifier is set to the correct voltage for your local AC
supply. If it is not, do not try to install the unit, and contact your
dealer.
Do not make connections, or insert or remove plugs, while
the unit is connected to the supply and switched on, as the
transients generated could damage the loudspeakers.
Once set up, the Stereo Power Amplifier can be left switched on
as it consumes negligible power when not in use.
If you are not going to use the Stereo Power Amplifier for a
period of several days you should switch the unit completely off,
at the back panel, and disconnect it from the AC power supply.
To position the Stereo Power
Amplifier
During normal operation the heatsinks, ie the fins at each end of
the case, may become quite hot. The Stereo Power Amplifier
should therefore be positioned to allow a free flow of air around
the fins.
Do not place the Stereo Power Amplifier:
❍In direct sunlight.
❍Near heat sources, eg a radiator.
❍Stacked with any other audio products, as the heat it
generates may damage the other products.

Setting up the Stereo Power Amplifier
9
Back panel
Connecting the Stereo Power Amplifier
OFF
ON
INPUT
LEFT
INPUT
RIGHT
BRIDGE MODE
BALANCED INPUT BALANCED INPUT
BRIDGE MODE
OFF
ON
BRIDGE MODE
INPUT
-
+
-
+
Input (R)
Bridge mode
switch
Outputs (R) Outputs (L) Input (L)
Balanced
input (R) Balanced input (L)

Setting up the Stereo Power Amplifier
10
Outputs
The following table gives details of the output connections:
Use this output To connect to this
LEFT, RIGHT Loudspeakers of 4Ωto 15Ω, using
either plug or bare wire connections.
BRIDGE MODE A loudspeaker of 6Ωto 15Ω; see To
wire to an A500 Loudspeaker in bridge
mode, page 12.
Each channel of the 557 Stereo Power Amplifier provides twin
outputs for bi-wiring. On speakers that provide separate
connections to the bass/mid and tweeter units this allows the
units to be connected independently to the Stereo Power
Amplifier, for optimum sound quality.
Alternatively, for loudspeakers providing a single pair of inputs,
either of the output terminals can be used.
Inputs
The following two alternative audio inputs are provided:
Use this input To connect to this
LEFT INPUT, A preamplifier, using phono connectors
RIGHT INPUT and high-quality screened cable.
BALANCED INPUTS A balanced analogue output, using
XLR connectors:
1 (Green) = GND
2 (Red) = +ve
3 (Black) = -ve
When using the balanced inputs the phono inputs should be
shorted, using the two phono shorting plugs supplied.

Setting up the Stereo Power Amplifier
11
To connect to A500 Loudspeakers
557 Stereo Power Amplifier
A500 LoudspeakerA500 Loudspeaker
●Set the BRIDGE MODE switch to the OFF position.
●Use the links provided to bridge the HF and LF terminals on
the back of each loudspeaker.
●Connect one of each pair of the red and black terminals on
the back panel of the 557 Stereo Power Amplifier to the red
and black terminals on the A500 Loudspeakers.
To connect to a conventional
preamplifier
●Connect the sockets marked INPUT on the back panel of the
Stereo Power Amplifier to the outputs from your preamplifier.
You should either use a twin-screened audio cable, or a pair of
single-screened audio cables. These cables can have a
considerable effect on the quality of the sound, and you are
advised to seek your dealer’s advice on the best type of cables
for your system.
To connect to a 501 Control Unit
OUTPUT
501 Control Unit
557 Stereo Power Amplifier
Audio lead
INPUT INPUT
●Connect the sockets marked OUTPUT L and R on the back
panel of the 501 Control Unit to the INPUT sockets on the
back panel of the 557 Stereo Power Amplifier.

Setting up the Stereo Power Amplifier
12
To wire to an A500 Loudspeaker in
bridge mode
557 Stereo Power Amplifier
A500 Loudspeaker
ON
Input
You can use the 557 as a mono power amplifier, to obtain more
than three times the power output, by wiring it in bridge mode.
●Switch the BRIDGE MODE switch to the ON position.
●Connect the audio input to only the LEFT INPUT or LEFT
BALANCED INPUT.
●Connect the loudspeaker between the red LEFT and RIGHT
terminals, leaving the black terminals unconnected.
To bi-wire to A500 Loudspeakers
557 Stereo Power Amplifier
A500 LoudspeakerA500 Loudspeaker
●Set the BRIDGE MODE switch to the OFF position.
●If necessary, remove the links bridging the LF and HF
terminals on the back of each loudspeaker.
●Connect the LF red and black terminals from each
loudspeaker to the red and black terminals on the appropriate
channel of the Stereo Power Amplifier, using twin loudspeaker
cable.
●Connect the HF red and black terminals from each
loudspeaker to the other pair of red and black terminals on
the appropriate channel of the Stereo Power Amplifier.

Setting up the Stereo Power Amplifier
13
●Fit the phono shorting plugs supplied with the Stereo Power
Amplifier to the unused phono input or inputs.
You can bi-wire in bridge mode by using the other pair of red
terminals to connect separately to the loudspeaker treble unit.
To bi-amp to two A500 Loudspeakers
557 Stereo Power Amplifier
A500 LoudspeakerA500 Loudspeaker
557 Stereo Power Amplifier
Extremely high sound quality can be achieved using two
separate 557 Power Amplifiers, one to drive each loudspeaker.
The two channels in each amplifier are used to drive the LF and
HF units in each loudspeaker.
●Switch the BRIDGE MODE on both amplifiers to the OFF
position.
●Connect the left audio output from the preamplifier to both
inputs on one amplifier.
●Connect the right audio output from the preamplifier to both
inputs on the other amplifier.
●If necessary, remove the links bridging the LF and HF
terminals on the back of each loudspeaker.
●Connect the red and black terminals from the LF and HF units
on one loudspeaker to the red and black terminals on each
channel of one amplifier.
●Likewise, connect the LF and HF units from the other
loudspeaker to the other amplifier.

Setting up the Stereo Power Amplifier
14
This section describes problems you may encounter when using
the Stereo Power Amplifier, and includes suggested solutions.
If these suggestions fail to cure the problem, please contact
your Meridian dealer for further assistance.
No front panel indicator is shown
❍Check that your AC power supply is connected correctly.
❍Check that the ON OFF switch on the back panel is in the ON
position.
❍Check that the fuse on the Stereo Power Amplifier back panel
and the fuse in the unit’s power plug have not blown; see To
change the mains fuse, page 15.
The output is noisy when using
balanced leads
❍Check that the phono inputs are shorted, using the two phono
shorting plugs supplied.
Troubleshooting
The sound has cut out
The 557 Stereo Power Amplifier includes a thermal shutdown,
which mutes the output if the amplifier becomes too hot.
❍Leave the amplifier for a few minutes to cool down, and the
sound will come back on.
The 557 Stereo Power Amplifier also includes a power circuit
breaker to protect the loudspeakers.
❍Check the system for the cause of the cut out.
❍Switch off, wait 5 seconds, then switch on to reset the power.
The sound has a muddled stereo
image and some information from the
right-channel is lost
❍Check that the BRIDGE MODE switch is OFF when using the
amplifier in stereo.
When the BRIDGE MODE switch is ON, and both left and right
inputs are connected, the left output will be the correct stereo
left signal, but the right output will be a left minus right signal.

Setting up the Stereo Power Amplifier
15
Maintenance
To clean the audio connections
The audio sockets on the back of the Stereo Power Amplifier are
gold-plated and need no cleaning if gold-plated phono plugs are
used. Otherwise, it is recommended that you unplug and
reconnect the plugs at least once a year. A proprietary contact
cleaner can be used to some advantage.
To change the mains fuse
Fuse
Spare
●Remove the mains connector, and pull out the drawer next to
the power input to access the fuses.
Before replacing a blown fuse, if possible ascertain the cause of
the failure.
The fuse drawer includes a spare fuse. This should be replaced
by one of the same rating.
Cleaning
When cleaning the Stereo Power Amplifier bear in mind that the
front of the unit is metal, and the lid is glass.
Disconnect the power cord before cleaning the unit.
Note: Do not use abrasive cleaners on any part of the Stereo
Power Amplifier.
To clean the case
●Use a slightly damp cloth.
Ensure that no water is allowed to get inside the case, and do
not reconnect the power until you are certain that the Stereo
Power Amplifier is completely dry.

Setting up the Stereo Power Amplifier
16
Service
The Meridian 500 Series of hi-fi components have been carefully
designed to give years of untroubled service. There are no user-
serviceable parts inside the case, nor do the units require any
form of maintenance.
In the unlikely event that your Stereo Power Amplifier fails to
function correctly, it should be returned, in its original
packaging, to your Meridian dealer.
In case of difficulty within the UK or USA please contact the
appropriate sales and service address shown on page ii.
In case of difficulty outside the UK or USA, contact the importing
agent for the territory. A list of Meridian agents abroad is
available from Meridian Audio.
No responsibility can be accepted for the Stereo Power
Amplifier whilst in transit to the factory or an agent, and
customers are therefore advised to insure the unit.
When seeking service under guarantee, proof of the date of
purchase will be required.
Guarantee
The 557 Stereo Power Amplifier is guaranteed against defects in
material and workmanship for two years from the date of
purchase.
The guarantee is void if the 557 Stereo Power Amplifier has been
subject to misuse, accident, or negligence, or has been
tampered with or modified in any way without the written
authorisation of Meridian Audio Limited. Attempted servicing by
unauthorised people may also invalidate this guarantee. Labour
and carriage charges are not covered unless by local agreement.
Outside the UK, local warranty liability is restricted to equipment
purchased within the territory. Our agents abroad are only under
contractual obligation to service under guarantee equipment
sold through them. They are entitled to make a non-refundable
charge for any service carried out on other equipment.
This guarantee does not limit your statutory rights within the
United Kingdom.
Service and guarantee