Alto MC250.8 Users Manual

MC250.8

User's Manual

EIGHT CHANNELS POWER AMPLIFIER

R

LTO

www.altoproaudio.com

Version 1.1 Nov. 2006

English

SAFETY RELATED SYMBOLS

CAUTION

RISK OFELECTRIC SHOCK

DO NOTOPEN

This symbol, wherever used, alerts you to the pre­sence of un-insulated and dangerous voltages with­in the product enclosure. These are voltages that
may be sufficient to constitute the risk of electric
shock or death.

This symbol, wherever used, alerts you to impo­rtant operating and maintenance instructions.
Please read.

Fuse

To prevent fire and damage to the product, use only
the recommended fuse type as indicated in this
manual. Do not short-circuit the fuse holder. Before
replacing the fuse, make sure that the product is
OFF and disconnected from the AC outlet.

Protective Ground

Before turning the product ON, make sure that it is
connected to Ground. This is to prevent the risk of
electric shock.

Never cut internal or external Ground wires. Likewise,
never remove Ground wiring from the Protective
Ground Terminal.

Protective Ground Terminal

AC mains (Alternating Current)

Hazardous Live Terminal

ON: Denotes the product is turned on.

OFF: Denotes the product is turned off.

WARNING

Describes precautions that should be observed to
prevent the possibility of death or injury to the user.

CAUTION

Describes precautions that should be observed to
prevent damage to the product.

Disposing of this product should not be
placed in municipal waste and should be
Separate collection.

WARNING

Power Supply

Ensure that the mains source voltage (AC outlet)
matches the voltage rating of the product. Failure
to do so could result in damage to the product and
possibly the user.

Unplug the product before electrical storms occur
and when unused for long periods of time to reduce
the risk of electric shock or fire.

External Connection

Always use proper ready-made insulated mains
cabling (power cord). Failure to do so could result
in shock/death or fire. If in doubt, seek advice from
a registered electrician.

Do Not Remove Any Covers

Within the product are areas where high voltages
may present. To reduce the risk of electric shock do
not remove any covers unless the AC mains power
cord is removed.

Covers should be removed by qualified service
personnel only.

No user serviceable parts inside.

Operating Conditions

Always install in accordance with the manufacturer's
instructions.

To avoid the risk of electric shock and damage, do
not subject this product to any liquid/rain or moisture.
Do not use this product when in close proximity to
water.

Do not install this product near any direct heat source.

Do not block areas of ventilation. Failure to do so
could result in fire.

Keep product away from naked flames.

IMPORTANT SAFETY INSTRUCTIONS

Read these instructions

Follow all instructions

Keep these instructions. Do not discard.

Heed all warnings.

Only use attachments/accessories specified by the
manufacturer.

Power Cord and Plug

Do not tamper with the power cord or plug. These are
designed for your safety.

Do not remove Ground connections!

If the plug does not fit your AC outlet seek advice from
a qualified electrician.

Protect the power cord and plug from any physical
stress to avoid risk of electric shock.

Do not place heavy objects on the power cord. This
could cause electric shock or fire.

Cleaning

When required, either blow off dust from the product
or use a dry cloth.

Do not use any solvents such as Benzol or Alcohol.
For safety, keep product clean and free from dust.

Servicing

Refer all servicing to qualified service personnel only.

Do not perform any servicing other than those instruc­tions contained within the User's Manual.

1

PREFACE

PREFACE

Thank you for choosing MC250.8 eight channel Power Amplifier and thanks for choosing one of the results of LTO

AUDIO TEAM job and research.

For our LTO AUDIO TEAM, music and sound are more than a job... is first of all passion and let us say our obsession!

We have been designing professional audio products for a long time in cooperation with some of the major brands
in the world in the audio field.

The LTO line presents unparalleled analogue and digital products made by Musicians for Musicians in our R&D
centers in Italy, Netherlands, United Kingdom and Taiwan. The core of our digital audio products is a sophisticated
Software Team for many years.

Following this idea we create our products and we will create the new ones! From our side, we guarantee you and
we will guarantee you also in future the best quality, the best fruits of our continuous researches and the best prices.

Nothing else to add, but that we would like to thank all the people that made the MC250.8 eight channels Power
Amplifier and thank our designers and all the LTO staff, people who make possible the realization of products
containing our idea of music and sound and are ready to support you , our customers, in the best way, conscious
that you are our best richness.

2

TABLE OF CONTENTS

1. INTRODUC IONT .............................................................................................................................................. .....4

2. FEATURES...................................................................................................................................... .. .............. ..... 4

3. CONTROL ELEMENTS............................................................................................................................... ........5

4.4. INSTALLATION.....................................................................................................................................................INSTALLATION.......................................................................................................................................................7

5. APPLICATION.........................................................................................................................................................8

6.

CAUTION FOR APPLICATION..............................................................................................................................10

7.

BLOCK DIAGRAM.................................................................................................................................................11

8.

TECHNICAL SPECIFICATIONS............................................................................................................................12

9.

WARRANTY...........................................................................................................................................................13

3

1. INTRODUCTION

The MC250.8 eight Channels Power Amplifier is designed for professional use and provides unparalleled quality. It

Includes soft start, signal limit, four variable-speed-low-noise fans, and includes eight independent channels with separate

power supply. Each channel is equipped with independent protective circuitry against open circuit, short circuit,

mismatched loads and overheat. Furthermore, every channel has also a protection LED that lights up before the

amplifier is in normal operation and flashes when the amplifier is in over-load protection or short-circuit protection, and

lights up when over-heat protection or DC protection occurs. CLIP LED that shows true amplifier clipping. The high

qualitycomponents and the carefully designed circuits ensure excellent audio performance and an extremely linear

frequency response, giving crystal-clear sound in the high range and an up-front, full-bodied bottom end. This amplifier

guarantees total reliability and a trouble-free use even in the most demanding conditions. We believe the MC250.8

not only look great, but provide a perfect performance, what you get is unprecedented performance at an incredibly

attractive price.

2. FEATURE

Innovative design and high stability power amplifier

Fan-cooled AB class high power amplifier in 19", 2U size

8

independent channels with separate protection system

DC, infrasonic, overheat & short circuit protection

Smart-designed protection system for auto re-operation after fault

Parallel-input: channel 1 to channel 2, channel 3 to channel 4, channel 5 to channel 6, channel 7 to channel 8

Allowing selection of Stereo, Bridge or parallel operation

Ultra low-noise and hum
High-pass filter , allow selection of flat, 35 Hz or 75Hz, protect speakers and prevent speaker transformer saturation

with minimal effect on program material.

DIP switch control for clip limit, high-pass filter, bridge-mono stereo selections

AUTO variable- speed-low-noise fans ensure high reliability even under demanding conditions.

Detachable Euroblock: " Barrier strip" input connectors.

Rugged amplifier in a strong, compact chassis

4

3. CONTROL ELEMENTS

3.1

The Front Panel

334 5

250W Professional Amplifier250W 8 ProfessionalAmplifier

24

6

28306

(dB)

24

6

28306

(dB)

PROT

CLP

PAR BRDG

PROT

CLP

PAR BRDG

20

18

8

2

1

6

4

6

2

1

(dB)

30

20

1

8

2

1

6

4

6

2

12

28306

(dB)

20

22

CH1 CH2

20

2

CH5 CH6

89

20

22

CH3

20

CH7

20

18

2

PROT

1

4

6

28306

(dB)

PAR

2

4

6

28306

(dB)

PAR

4

6

12

CLP

28306

SGSG

(dB)

CH4

BRDG

20

1

2

PROT

1

4

6

12

CLP

28306

SGSG

(dB)

CH8

BRDG

LTO

R

7

MC250.8

Power Switch

1

2

18

16

PWRON

12

ON

18

16

OFF

12

POWER

6

1

It switches on / off MC250.8 main power.

Power LED

2

This LED lights up when the amplifier is powered on

Clip LED

When the respective channel's output signal distortion exceeds 0.5%, the red LED (clip) indicator lights up. it
will warn you that the level of the input signal is too high and may cause distortion, please attenuate the level
of the input signal.

Protection LED

4

This red LED indicator lights up when the amplifier is powered ON, and the soft-start protection system is working.
No sound is outputted during soft-start protection. If short-circuit protection or over-load protection is activated

this indicator flashes and no sound is

outputted.

The speakers system is actually disconnected with the amplifier
outputs when this indicator flashes. when over-heat protection or DC protection is activated. At this time, protection
LED lights up, and audio output is shut down automatically, and no sound is outputted. When the amplifier have
no malfunction, all the protection systems deactivate and protection LED lights off.

Signal LED

5

After signal is inputted, LED becomes brighter while the signal level increases.

6

Level Control

This pot is used to adjust output level.

7

Fan

The unit is equipped with two fans in the front, which can accelerate the flow of air to lower the temperature inside
unit. The inside temperature determines the fan speed, which controls the inside air flowing speed.

Bridge Mode LED Indicator

8

When you operate the unit in bridge mode, the LED indicator lights up. As for the bridge mode, refer to 3.2 rear
panel

11

,

Parallel Mode LED Indicator

9

When you operate the unit power amplifier in parallel mode, the LED indicator lights up. As for the parallel mode,
refer to 3.2 rear panel

11

5

3.2 The Rear Panel

CH7

CH7

CH8

CH8

CH7

CH7

MODESWITCHES

MODESWITCHES

Apparaten skall anslutas

Apparaten skall anslutas
till jordat uttag nar den

CH5

CH5

CH6

CH6

CH8

CH8

CH5

CH5

MODESWITCHES

MODESWITCHES

CH6

CH6

INPUTS

INPUTS

CH3

CH3

CH4

CH4

CH3

CH3

MODESWITCHES

MODESWITCHES

CH1

CH1

CH2

CH2

CH1

CH1

CH4

CH4

12345678910123456789101234567891012345678910

12345678910123456789101234567891012345678910

MODESWITCHES

MODESWITCHES

CH2

CH2

CH1 CH2 CH3 CH4

CH1 CH2 CH3 CH4

CH5 CH6 CH7 CH8

CH5 CH6 CH7 CH8

RDGE

RDGE
MONO

MONO

OUTPUTS

OUTPUTS

till jordat uttag nar den
ansluts ti l ett natverk

ansluts ti l ett natverk

BREAKER

BREAKER

BRIDGE

BRIDGE

MONO

MONO

AC NPUT

AC NPUT

10

10

INPUT Terminal

15

This unit is provided with balanced terminals, which are used to connect the input signal. Channel 1

11

12

and channel 2

are used in bridge and parallel mode.

Mode Selector

11

You can choose the right function and output you need via the mode selector switch. In order to make you acquire

these settings, now let me introduce the dip switch.

345678910

12

This switch is made up of 10 small dip switches, these small dip switches from1 to 5 control one channel, these
rest ones (6-10 ) control the other channel, ok, you can choose the right mode setting you need via these small

dip switches. Take the dip switch of channel 1 and channel 2 for example. Channel 3 and channel 4 are the same
as channel 1 and channel 2

- Output Mode Selector

14

13

This unit provides three output modes: stereo, bridge and parallel. Here are some details:

set the small dip switches 4, 5, 6, 7 down to the bottom, then channel 1 and channel 2 are in stereoStereo mode:

mode;

STEREO MODE

12345678910

Parallel mode: set the small dip switchesf 4, 5, 6, to the top, and the small dip switch 7 down, then channel
1 and channel 2 are in parallel mode.

PARALLEL MODE

12345678910

Bridge mode: set the small dip switch 7 up to the top, and the dip switches 4,5,6 to the bottom, then channel 1 and
channel 2 are in bridge mode.

BRIDGE MODE

1234

5678910

Please refer to chapter 5 for the connection of loads in detail.

6

- function selector

Clip limit : set these small dip switches of 1(ON) and 10(ON) at "ON" position , then the clip limit of channel 1

and channel 2 has been working; once the output level is reach or exceed the level that is predetermined by the

threshold setting selected, it may result in the undesirable distortion .in order to avoid the distortion, the clip begins;
if the dip switch are set at "OFF", the clip limit doesn't work.

CLIP LIMIT

ON

23456789

ON

OFF

Filter: this unit are equipped with two low cut filter eliminating unwanted low- frequency signals like rumble noise:
75Hz and 35Hz. When 2& 9 are set to the top position, set 3&8 to the top position, 35Hz low cut filter is activated.
Set 3&8 to the bottom position, 75Hz low cut filter is activated.

FILTER ON

35Hz FILTER

5

FILTER OFF

4

75Hz FILTER

1

Output Terminal

12

You can output the powered signal by the specific output connectors according to the actual application circumstance.
When the output terminal is connected with speaker, you can complete the connection as the way we signed in this manual
Caution: turn off the unit before connecting the output connectors so as to avoid any electric shock!

Breaker

13

This switch works as fuse for protecting the unit from damage. When the unit is overloaded or the temperature
inside the unit is too high, this push-button will spring up and break the power supply. The power supply will be
restored with pushing this switch again.

OFF

FILTER ON

67 10

35Hz FILTER

FILTER OFF

75Hz FILTER

14

AC-Inlet

This standard IEC receptacle is supplied to allow to connect your MC250.8 to mains via the supplied power cord.

15

Fans on rear panel

The unit is equipped with two fans in the back, which can accelerate the flow of air to lower the temperature inside
unit. The inside temperature determines the fan speed, which controls the inside air flowing speed.

4. Installation

4.1 Mains connection

Do not insert the power cord into this unit until voltage has been correctly set. Please confirm if the power cord is

connected correctly . Please ensure that the MC250.8 professional power amplifier is supplied with the correct voltage

before turning on this unit. If you can't power up this unit while turning on the mains switch (1), check the Breaker

(14) on the rear panel first, and check if it is in the release state. Otherwise, contact the technician or qualified

personnel for checking if the unit power is 3000W or for any other service.

Caution: To reduce the risk of electric shock, do not perform any servicing other than contained in this manual unless

you are qualified to do so. Please turn off this unit before any installation and connection, esp. when you connect

your unit into the sound system. This is important to prevent damage to the unit itself as well as other consequent

speaker system. This is important to prevent damage to the unit itself as well as other consequent speaker system.

The mains connection of the MC 250.8 professional power amplifier is made by using the enclosed power cord and

a standard IEC receptacle, and it meets all of the international safety certification requirement.

7

4.2 Rack Mounting

the most secure mounting is on a universal rack shelf available from various rack manufactures or your music dealer.
The MC250.8 professional power amplifier fits into one standard 19" rack unit of space. Be sure that there is enough
air space around the unit for sufficient ventilation. If heat release is inadequate, this unit will retain heat inside, which
may cause the protection, or even a fire.

5. Application

The MC250.8 provides three operating modes with each unit: stereo mode, parallel mode and bridged mode, you

can decide each specific operating mode according to your actual application circumstance. Following examples will

show you the typical connections, you can refer to install your MC250.8 into a sound system:

5.1 Operate MC250.8 Power Amplifier In Stereo Mode

In this mode, each channel works independently. The signal inputted from one channel will be outputted from the
corresponding channel.

Appara en skall anslutas

CH7

CH8

CH5

CH6

CH3

CH4

CH1

CH2

CH1 CH2 CH3 CH4

t ll jordat uttag nar den
ansluts till ett natverk

BREAKER

Channel 1

CH7

MODESWITCHES

CH8

CH5

MODESWITCHES

CH6

CH3

MODESWITCHES

INPUTS

Channel 2

STEREO MODE

12345678910

CH1

12345678910123456789101234567891012345678910

MODESWITCHES

CH2

CH5 CH6 CH7 CH8

BRI GE

BRDGE

MONO

MONO

OUTPUTS

AC INPUT

CH4

Channel 2

+

+

+

Channel 1

8

5.2 Operate MC250.8 Power Amplifier In Parallel Mode

In this mode, the channel 1 input signal will be output from the output connectors of both channel 1 and channel

2. The channel 2 input jack is not used. The channel 1 and channel 2 volumes can be adjusted independently.
Furthermore, channel1 can only be parallelled with channel2, channel 3 only with channel 4, channel 5 only with
channel 6, and channel 7 only with channel 8.

Apparaten ska l anslutas

CH7

CH8

CH7

MODESWITCHES

CH5

CH6

CH8

CH5

MODESWITCHES

CH3

CH4

CH6

CH3

MODESW TCHES

INPUTS

CH1

CH2

CH1

CH4

12345678910123456789101234567891012345678910

MODESWITCHES

CH2

CH1 CH2 CH3 CH4

CH5 CH6 CH7 CH8

BRI GE

MONO

OUTPUTS

t ll jordat uttag nar den
ansluts t ll ett natverk

BREAKER

BRDGE

MONO

AC INPUT

Channel 1

Channel 2

+

+

PARALLEL MODE

12345678910

Channel 1

+

5.3 Operate MC250.8 In Bridge Mode

In this mode, signal inputted from channel1can be output from the bridge output connectors. In this case, use the channel 1
volume control to adjust the volume. Turn the volume control of channel2 counterclockwise completely. Then, you can

control the volume of the whole system by adjusting the channel 1 volume control. Furthermore, channel1 can be bridged

with channel2 only, channel3 with channel4 only, channel5 with channel 6 only, and channel 7 with channel 8 only.

Apparaten ska l anslutas

CH7

CH8

CH7

MODESWITCHES

CH5

CH6

CH8

CH5

MODESWITCHES

CH3

CH4

CH6

CH3

MODESW TCHES

INPUTS

CH1

CH2

CH1

CH4

12345678910123456789101234567891012345678910

MODESWITCHES

CH2

CH1 CH2 CH3 CH4

CH5 CH6 CH7 CH8

BRI GE

MONO

OUTPUTS

t ll jordat uttag nar den
ansluts t ll ett natverk

BREAKER

BRDGE

MONO

AC INPUT

Channel 1

+

BRIDGE MODE

1234

5678910

9

6.CAUTION FOR APPLICATION

6.1 General Application instruction

the following instructions describe the common ways to install your MC250.8 power amplifier into a sound application
system:

First, turn off power switch before connection.

Refer to chapter 5 for speaker connection

MC250.8 power amplifier may be operated in one of the three modes, please slide the mode selector for the
Specific operating mode

6.2 caution for speak connection

The output capacity of MC 250.8 power amplifier is very high, be sure to use a speaker system that has sufficient
input capacity. If the input capacity of your speaker system is lower than the rated output of the MC250.8 power
amplifier, you can protect your speakers by connecting a fuse serially between the speaker and the amplifier
as shown below.

(+)

Fuse

(-)

Output

Apparaten skall anslutas

CH7

CH8

CH5

CH6

CH3

CH4

CH1

CH2

CH1 CH2 CH3 CH4

ti l jordat uttag nar den
ansluts ti l ett natverk

BREAKER

+

Speaker

-

System

CH1

12345678910123456789101234567891012345678910

MODESWITCHES

CH2

CH5 CH6 CH7 CH8

BRDGE

BRIDGE

MONO

MONO

OUTPUTS

AC INPUT

CH7

MODESWITCHES

CH5

MODESWITCHES

CH6

INPUTS

CH8

CH3

MODESWITCHES

CH4

Use the following formula to determine the fuse capacity according to the speaker's input capacity.

2

Po=I R I= Po/R
Po[W] : Speaker's continuous input capacity (noise or RMS)
R[ ] : Speaker's nominal impedance
I[A] : Required fuse capacity

As to the speaker cable, if you use a long one, use as thick a cable as possible to prevent deterioration of the
damping factor or power loss inside the cable.

10

7. BLOCK DIAGRAM

11

8. TECHNICAL SPECIFICATION

Model

Output Power
20Hz 20kHz @0.1%THD , stereo Mode
8 ohms per channel (EIAJ)
4 ohms per channel (EIAJ)
Bridge Mono Mode
8 ohms, 1kHz, 0.1% THD (EIAJ)
Distortion (SMPTE-IM)
Frequency Response
Damping Factor, 1kHz, 0.1%THD(EIAJ)
Signal to Noise, 20Hz-20kHz
Voltage Gain
Input sensitivity @ 4 ohms
Input clipping
Input impedance
Controls

Indicators

Connectors, each channel

cooling
Load protection
Power supply
Dimensions

Net weight

MC250.8

8x180W
8x250W

4500W
<0.05%

20Hz- 20kHz 1dB, -3dB point: 10Hz- 60kHz

>300@8 ohms

90dB
40 ( 32dB)

1Vrms
10 Vrms (+22dB)
10Kohms unbalanced, 20 Kohms balanced
Front: AC Switch, Ch1 - Ch8 Gain Knobs
Rear: MODE SWITCHES

Power - On: Blue LED

Protection: Red LED
Signal: LEDGreen
Clip: Red LED

Parallel-input: Yellow LED
Bridge: Yellow LED

Input: Terminal Block
Output: Screw-terminal Barrier Block

Continuously variable- speed fan, front - to - rear air flow

On / Off muting, overheat & short circuit protection

220-240 ( 110-120) Vac 50-60 Hz

17.7" ( 44.95 cm) (D)* 3.5" ( 8.9 cm) (H)*19.02"(48.3 cm)(L)

21.6Kg

12

9. WARRANTY

1. WARRANTY REGISTRATION CARD

To obtain Warranty Service, the buyer should first fill out and return the enclosed Warranty Registration Card within
10 days of the Purchase Date.

All the information presented in this Warranty Registration Card gives the manufacturer a better understanding of
the sales status, so as to purport a more effective and efficient after-sales warranty service.

Please fill out all the information carefully and genuinely, miswriting or absence of this card will void your warranty
service.

2. RETURN NOTICE

2.1 In case of return for any warranty service, please make sure that the product is well packed in its original shipping
carton, and it can protect your unit from any other extra damage.

2.2 Please provide a copy of your sales receipt or other proof of purchase with the returned machine, and give detail
information about your return address and contact telephone number.

2.3 A brief description of the defect will be appreciated.

2.4 Please prepay all the costs involved in the return shipping, handling and insurance.

3. TERMS AND CONDITIONS

3.1 warrants that this product will be free from any defects in materials and/or workmanship for a period

LTO

of 1 year from the purchase date if you have completed the Warranty Registration Card in time.

3.2 The warranty service is only available to the original consumer, who purchased this product directly from the
retail dealer, and it can not be transferred.

3.3 During the warranty service, may repair or replace this product at its own option at no charge to you for

LTO

parts or for labor in accordance with the right side of this limited warranty.

3.4 This warranty does not apply to the damages to this product that occurred as the following conditions:

Instead of operating in accordance with the user's manual thoroughly, any abuse or misuse of this product.

Normal tear and wear.

The product has been altered or modified in any way.

Damage which may have been caused either directly or indirectly by another product / force / etc.

Abnormal service or repairing by anyone other than the qualified personnel or technician.

And in such cases, all the expenses will be charged to the buyer.

3.5 In no event shall be liable for any incidental or consequential damages. Some states do not allow the exclu-

LTO

sion or limitation of incidental or consequential damages, so the above exclusion or limitation may not apply to you.

3.6 This warranty gives you the specific rights, and these rights are compatible with the state laws, you may also
have other statutory rights that may vary from state to state.

13

SEIKAKU TECHNICAL GROUP LIMITED

SEKAKU ELECTRON INDUSTRY CO., LTD.

No. 1, Lane 17, Sec. 2, Han Shi West Road, Taichung 40151, Taiwan

http://www.altoproaudio.com Tel: [phone]

email: [e-mail] Fax: [phone]

All rights reserved to ALTO. All features and content might be changed

without prior notice. Any photocopy, translation, or reproduction of part of this

manual without written permission is forbidden. Copyright 2006 SEIKAKU GROUP

c

NF02620 1.1