Alto MC250.4 Users Manual

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MC250.4

User's Manual

FOUR CHANNELS POWER AMPLIFIER

LTO

www.altoproaudio.com

Version 1.0 AUGUST 2005

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.

PREFACE

Thank you for choosing MC250.4 four channels 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 MC250.4 four 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.

TABLE OF CONTENTS

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

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

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

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

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

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

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

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

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

1. INTRODUCTION

The MC250.4 Four Channels Power Amplifier is designed for professional use and provides unparalleled quality. It

Includes soft start, signal limit, two variable-speed-low-noise fans and a LED meter display. Each channel is equipped

with independent protective circuitry against open circuit, short circuit, mismatched loads and overheat. It includes four

independent channels with separate power supply. Furthermore, every channel has also a main LED that becomes

green for power-on indicator and green for muting or protection, another red LED that shows true amplifier clipping

and a yellow one for the limit stage. The high-quality components 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 MC250.4 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

4 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

Allow 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 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

3. CONTROL ELEMENTS

3.1

The Front Panel

MC250.4

PWR ON

OFF

POWER

Power Switch

334 5

250W 4 Professional Amplifier

CLIP

PROT

C P

CLIP

PROT

-10dB

10dB

LIMIT

-20dB

20dB

BRDG

LEVEL P R LEVEL

2836

(dB)

CH1

CH2

998

LEVEL PAR LEVEL

28306

dB)

CH3

CLIP

-10dB

L M T

-20dB

BRDG

28306

(dB)

CH4

LTO

It switches on / off MC250.4 main power.

Power LED

This LED lights up when the amplifier is powered on

Input Level Indicator Display

There are three high accurate LED indicators, which shows the level of the input signal. 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

This green LED indicator lights up when the amplifier is powered ON, indicating that the soft-start protection system is working. No sound is output during soft-start up. if one of the protection systems is activated during normal use, this indicator lights up and no sound is output. The speakers system is actually disconnected from the amplifier outputs when this indicator lights up. The protection systems are activated when overheating occurs or a DC voltage is corrected, the protection systems deactivate automatically, this indicator goes out, and normal amplifier operation is resumed.

Output Limiter LED

Set the clip limit switch at "ON" position, the yellow LED lights up when the unit is limiting the output signal.

Level Control

This pot provides smooth level changes control.

Fan

The unit is equipped with two fans, 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

When you operate the unit in bridge mode, the LED indicator lights up .

Parallel Mode LED Indicator

When you operate the unit power amplifier in parallel mode, the LED indicator lights up

3.2 The Rear Panel

INPUTS

CH2

CH4

FILTERS

35HzF LTER

FLTER ON

67 10

FLTER OFF

75HzF LTER

CH1MODE SWITCHES CH2

CH3MODE SWITCHES CH4

PARALLELMODE

35HzF LTER

75HzF LTER

BRIDGE MONO

FLTER ON

BRIDGEABLE CHANNEL PAIRS

CH1AND CH2 CH3AND CH4

TOBR DGE CHANNEL PA RS SET INPUT SW TCHES AS SHOWN USE THE LOWER NUMB RED CHANNEL S INPUT

FLTER OFF

ANDGAIN CONTROL CONNECT SPEAKERAS SHOWN

12345678910

678910

SWITCH SETTINGS 1234567

8910

BRIDGE

MONO

CH2

OUTPUTS

MODEL

SERIAL

INPUT Terminal

CH1

CH3

MODE SWITCH SETT NGS

CLIP L MIT

6789

OFFONOFF

STEREO MODE

678910

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

Apparatenska l anslutas til jordat uttag nar den anslutsti l ett natverk

CH3CH1

BRIDGE

MONO

CH4

OUTPUTS

and channel 3

BREAKERBREAKER

AC INPUT

are used in bridge and parallel mode.

Mode Selector

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

Useonly w th a 250V use

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

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

turn these small dip switches of 4, 5, 6, 7 up to the top, then channel 1 and channel 2 are inStereo mode: stereo

mode;

STEREO MODE

12345678910

Parallel mode: turn these small dip switches of 4, 5, 6, to the top, and turn the small dip switch of 7 down, then

channel 1 and channel 2 are in parallel mode.

PARALLEL MODE

12345678910

Bridge mode: turn these small dip switch of 7 up to the top, then channel 1 and channel 2 are in bridge mode.

BRIDGE MODE

1234

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

5678910

- 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

23456789

OFF

Filter: this unit are equipped with two low cut filter eliminating unwanted low- frequency signals like rumble noise: 75Hz and 35Hz. You will activate 35Hz low cut filter by Turning these two small dip switches of 2 and 9 up to the top, and turn these two small dip switches down, you will choose 75Hz low cut filter.

FILTER ON

35Hz FILTER

67 10

FILTER OFF

75Hz FILTER

Output Terminal

You can output the powered signal by the specific output connectors according to the actual application circumstance.

Caution: turn off the unit before connecting the output connectors so as to avoid any electric shock!

OFF

35Hz FILTER

FILTER ON

FILTER OFF

75Hz FILTER

Breaker

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.

AC-Inlet

This standard IEC receptacle is supplied to allow to connect your MC250.4 to mains via the supplied power cord.

4. Installation

4.1 Mains connection

Do not insert the power cord into this unit until voltage has been correctly set. Do not plug the power cord into the

mains until the voltage has been correctly set. Please ensure that the MC250.4 professional power amplifi ris

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 fist, maybe it is pressed to reset. Otherwise, contact the

technician or qualified personnel for any 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 250.4 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.

4.2 Rack Mounting the most secure mounting is on a universal rack shelf available from various rack manufactures or your music dealer. The MC250.4 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 MC250.4 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 MC250.4 into a sound system:

5.1 Operate MC250.4 Power Amplifier In Stereo Mode

In this mode, channel 1 and channel 2 operate independently ( as a conventional stereo amp).The channel 1 input signal will be output from the channel 1 output jacks, and the channel 2 input signal will be output form the channel 2 output jacks.(take channel 1 and channel 2 for example)

MODEL

SERIAL

Channel 1

CH1

CH3

MODE SWITCH SETT NGS

CLIP LIMIT

6789

OFFONOFF

STEREO MODE

678910

INPUTS

CH2

CH4

FILTERS

FLTER ON

35HzF LTER

FLTER ON

35HzF LTER

67 10

BRIDGEABLE CHANNEL PAIRS

CH1AND CH2 CH3AND CH4

TOBR DGE CHANNEL PA RS SET INPUT SW TCHES AS SHOWN USE THE LOWER NUMBERED CHANNEL S INPUT

FLTER OFF

75HzF LTER

ANDGAIN CONTROL CONNECT SPEAKERAS SHOWN

Channel 2

STEREO MODE

12345678910

CH1MODE SWITCHES CH2

12345678910

CH3MODE SWITCHES CH4

12345678910

PARALLELMODE

678910

BRIDGE MONO

SWITCH SETTINGS 1234567

8910

BRIDGE

MONO

CH2

OUTPUTS

CH3CH1

BRIDGE

MONO

CH4

OUTPUTS

Channel 1

Channel 2

Apparatenska l anslutas til jordat uttag nar den anslutsti l ett natverk

BREAKERBREAKER

AC INPUT

Useonly w th a 250V use

5.2 Operate MC250.4 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.

MODEL

SER AL

5.3 Operate MC250.4 In Bridge Mode

Channel 1

CH1

CH3

MODE SWITCH SETTINGS

CLIP LIMIT

6 7 89

OFFONOFF

STEREO MODE

678910

INPUTS

CH2

CH4

FILTERS

FLTER ON

35HzF LTER

67 10

FLTER OFF

75HzF LTER

CH1MODE SWITCHES CH2

CH3MODE SWITCHES CH4

PARALLELMODE

35HzF LTER

75HzF LTER

BRIDGE MONO

FLTER ON

BRIDGEABLE CHANNE PAIRS

CH1AND CH2 CH3AND CH4

TOBRIDGE CHANNEL PAIRS SET NPUTSWITCHES AS SHOWN USE THE LOWER NUMBERED CHANNEL S NPUT

FLTER OFF

ANDGA N CONTROL CONNECT SPEAKERAS SHOWN

12345678910

678910

SW TCH SETTINGS 1234567

8910

PARALLEL MODE

12345678910

BR DGE

MONO

CH2

OUTPUTS

CH3CH1

BRIDGE

MONO

CH4

OUTPUTS

Channel 1

Channel 2

Apparatenskall anslutas

illjordat uttag nar den

ansluts illett natverk

BREAKERBREAKER

AC NPUT

Useon y wi h a 250V fuse

In this mode, the channel 1 input signal will be output from the bridge output connectors. In this case, use the channel 1 volume control to adjust the volume. keep the volume control of channel 2 turned completely down (counterclockwise). Then, you can control the volume of the whole system by adjusting the channel 1 volume control.

MODEL

SER AL

Channel 1

CH1

CH3

MODE SWITCH SETTINGS

CLIP LIMIT

6789

OFFONOFF

STEREO MODE

678910

INPUTS

CH2

CH4

FILTERS

FLTER ON

35HzF LTER

67 10

FLTER OFF

75HzF LTER

CH1MODE SWITCHES CH2

CH3MODE SWITCHES CH4

PARALLELMODE

35HzF LTER

75HzF LTER

BRIDGE MONO

FLTER ON

BRIDGEABLE CHANNEL PAIRS

CH1AND CH2 CH3AND CH4

TOBRIDGE CHANNEL PAIRS SET NPUTSWITCHES AS SHOWN USE THE LOWER NUMBERED CHANNEL S NPUT

FLTER OFF

ANDGA N CONTROL CONNECT SPEAKERAS SHOWN

12345678910

678910

SW TCH SETTINGS 1234567

8910

BR DGE

MONO

CH2

OUTPUTS

CH3CH1

BRIDGE

MONO

CH4

OUTPUTS

Apparatenskall anslutas

illjordat uttag nar den

ansluts illett natverk

BREAKERBREAKER

AC NPUT

Useon y wi h a 250V fuse

BRIDGE MODE

1234

5678910

6.CAUTION FOR APPLICATION

6.1 General Application instruction

the following instructions describe the common ways to install your MC250.4 power amplifier into a sound application system:

First, turn off power switch before connection.

Refer to chapter 5 for speaker connection

MC250.4 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 250.4 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 MC250.4 power amplifier, you can protect your speakers by connecting a fuse serially between the speaker and the amplifier as shown below.

MODEL

SERIAL

CH1

CH3

MODE SWITCH SETTINGS

CLIP LIMIT

6789

OFFONOFF

STEREO MODE

678910

(+)

(-)

Output

INPUTS

CH2

CH4

FILTERS

FLTER ON

35HzF LTER

67 10

FLTER OFF

75HzF LTER

CH1MODE SWITCHES CH2

CH3MODE SW TCHES CH4

PARALLELMODE

35HzF LTER

FLTER ON

BRIDGEABLE CHANNEL PAIRS

CH1AND CH2 CH3AND CH4

TOBRIDGE CHANNEL PA RS SET NPUTSW TCHES AS SHOWN USE THE LOWER NUMBERED CHANNEL S INPUT

FLTER OFF

ANDGAIN CONTROL CONNECT SPEAKERAS SHOWN

75HzF LTER

12345678910

678910

BRIDGE MONO

SWITCH SETTINGS 1234567

8910

BRIDGE

MONO

CH2

OUTPUTS

Fuse

CH3CH1

BRIDGE

MONO

CH4

OUTPUTS

Apparatenskall anslutas til jordat uttag nar den anslutst ll ett natverk

BREAKERBREAKER

AC INPUT

Useonly w th a 250V fuse

Speaker System

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

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.

7. BLOCK DIAGRAM

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

MC250.4

4x180W 4x250W

2500W <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 - Ch4 Gain Knobs Rear: MODE SWITCHS

Power - On: Blue LED

Protection: Green LED LIMITER:YellowLED Clip: Red LED

Parallel-input: Yellow LED Bridge: Yellow LED Level: Green LED (-20 and -10dB)

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

19" ( 48.3 cm) rack mounting, 3.5" ( 8.9 cm) tall(2rackspaces),

15.9" ( 40.3 cm) deep ( rack mounting to rear support ears) 17Kg

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.

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: 886-4-22313737

email: alto@altoproaudio.com Fax: 886-4-22346757

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

NF02244 1.0

Alto MC250.4 Users Manual

Specifications and Main Features

Frequently Asked Questions

User Manual