Alto D1 User manual

MULTI-CHANNEL POWER AMPLIFIER
LTO
R
www.altoproaudio.com
Version 1.0 Oct. 2006
English
User's Manual
D1
D2
D3
D4

1
SAFETY RELATED SYMBOLS
CAUTION
RISK OF ELECTRIC SHOCK
DO NOT OPEN
Protective Grounding
The symbol is used to indicate that some hazard-
ous live terminals are involved within this apparatus,
even under the normal operating conditions.
The symbol is used in the service documentation
to indicate that a specific component shall be only
replaced by the component specified in that docu-
mentation for safety reasons.
Protective grounding terminal.
Alternating current /voltage.
Hazardous live terminal.
ON: Denotes the apparatus is turned on.
OFF: Denotes the apparatus is turned off, because it uses
the single pole switch, be sure to unplug the AC power to
prevent any electric shock before you proceed with your
service.
WARNING: Describes precautions that should be
observed to prevent the danger of injury or death to
the user.
CAUTION: Describes precautions that should be
observed to prevent danger of the apparatus.
WARNING
Power Supply
Ensures the source voltage matches the voltage of the
power supply before turning ON the apparatus.
Unplug this apparatus during lightning storms or when
unused for long periods of time.
External Connection
Do not Remove any Cover
There are maybe some areas with high voltages inside,
to reduce the risk of electric shock, do not remove any
cover if the power supply is connected.
The cover should be removed by qualified personnel
only.
No user serviceable parts inside.
Fuse
dis-connect the power source.
Operating Conditions
This apparatus shall not be exposed to dripping or spl-
ashing and that no objects filled with liquids, such as
vases, shall be placed on this apparatus.
To reduce the risk of fire or electric shock, do not expose
this apparatus to rain or moisture.
Do not use this apparatus near water.
Install in accordance with the manufacturer's instructions.
Do not install near any heat sources such as radiators,
heat registers, stoves, or other apparatus (including amp-
lifiers) that produce heat.
Do not block any ventilation openings.
No naked flame sources, such as lighted candles, should
be placed on the apparatus.
IMPORTANT SAFETY INSTRUCTIONS
Read these instructions.
Heed all warnings.
Follow all instructions.
Keep these instructions.
Only use attachments/accessories specified by the manu-
facturer.
Power Cord and Plug
Do not defeat the safety purpose of the polarized or
grounding type plug. A polarized plug has two blades
with one wider than the other. A grounding type plug
has two blades and a third grounding prong. The wide
blade or the third prong are provided for your safety.
If the provided plug does not fit into your outlet, consult
an electrician for replacement of the obsolete outlet.
Protect the power cord from being walked on or pinched
particularly at the plug, convenience receptacles, and
the point where they exit from the apparatus.
Cleaning
When the apparatus needs a cleaning, you can blow off
dust from the apparatus with a blower or clean with a rag
etc. Don't use solvents such as benzol, alcohol, or other
fluids with very strong volatility and flammability for cleaning
the apparatus body.
Clean only with a dry cloth.
Servicing
Refer all servicing to qualified personnel. To reduce the
risk of electric shock, do not perform any servicing other
than that contained in the operating instructions unless
you are qualified to do so.
Servicing is required when the apparatus has been dam-
aged in any way, such as the power supply cord or plug
is damaged, liquid has been spilled or objects have fallen
rain or moisture, does not operate normally, or has been
dropped.
into the apparatus, the apparatus has been exposed to
Make sure to connect the protective grounding to prevent
any electric shock before turning ON the apparatus.
To prevent a fire, make sure to use fuses with specified
standard (current, voltage, type). Do not use a different
fuse or short circuit the fuse holder.
Before replacing the fuse, turn OFF the apparatus and
The external wiring connected to the output hazardous
live terminals requires installation by an instructed person,
or the use of ready-made leads or cords.
Never cut off the internal or external protective grounding
wire or disconnect the wiring of protective grounding terminal.

2
Preface
Dear Customer:
Thanks for choosing LTO D series Multi-channel Power Amplifier and thanks for choosing one of The results of LTO
AUDIO TEAM job and researches.
For our LTO AUDIO TEAM, music and sound are more than a job ...are 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 DSP (Digital
Sound Processor) and a large range of state of the art algorithms which have been developed by our Software Team for
the last 7 years.
Because we are convinced you are the most important member of LTO AUDIO TEAM and the one confirming the quality
of o and your comments.ur job, we'd like to share with you our work and our dreams, paying attention to your suggestions
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, and the best fruits of our continuous researches and the best prices.
Our LTO D series Stereo Power Amplifier is the result of many hours of listening and tests involving common people,
area experts, musicians and technicians. The result of this effort is the sophisticated circuit design featuring high power
and superb quality together with superior reliability and stability to provide the highest possible audio performance.
Nothing else to add, but that we would like to thank all the people that made the LTO D series Multi-channel Power Amplifier a
reality available to our customers, and thank our designers and all the LTO staff, there to make possible the realization of
products containing our idea of music and sound and there to support you, our customers, In the best way, conscious that you
are our best richness.
Thank you very much.
LTO AUDIO TEAM

TABLE OF CONTENTS
1. INTRODUCTION...................................................................................................................... .........4........
2. FEATURES .... .........................................................................................................................................4
3. CONTROL ELEMENTS ........................................................................... .................................................5
3.1 The Front Panel
3.2 The Rear Panel
4. APPLICATION .................................................................................................. .....................................8
4.1 Stereo Mode
5. TECHNICAL SPECIFICATIONS ................................................................................................... .......9
6. WARRANTY ........... ................................................................................. ............................................10
3
4.2 Bridge Mode

Signal LED
Green LED, This LED lights up green when the output level reaches -20dB.
2
4
1. D SERIESLTO
2. FEATURES
Fantastic audio quality even with extremely high volume levels.
Solid and durable, can be mounted into a cabinet.
Automatic limiter
Stereo (dual-channel), or bridge mono operating modes.
Balanced XLR, 6.3 inputs / parallel outputs to ensure noiseless long wiring.
Binding post and professional speak-on connectors for output.
Stereo, bridge, and parallel output wiring possibility.
Front panel LED indicators for power-on, signal, protection and clip.
Accurate gain control
Independent DC, thermal, overload and short-circuit protection on each channel automatically protects amplifier
and speakers.
Used together with line array cabinet in one audio system
Manufactured under TS16949, ISO 14001 certified management system and RoHS directive.
2U rack, multi-channel high power amplifier.
The D series includes D1, D2, D3, D4. It is a line of high power, low profile, professional Power Amplifiers withLTO
advanced features and great reliability. They deliver tremendous power in only two rack spaces, providing high level
performance under the most demanding conditions. An automatic speed fan matches cooling capacity with heat
requirements. The amplifier frame contains all solid-state circuitry, using complementary silicon output devices. The
amplifier is supplied with a single moulded AC cord having an appropriate AC plug for the intended operating voltage.
The amplifier employs forced air cooling with a variable speed fan for minimum acoustic noise. Air flow is from rear to
front to avoid temperature rise inside the Rack. D1, D3 contain two independent channels and D2, D4 contain four
independent channels, with separate AC transformer secondaries, power supplies and protection system. All protection
systems, except the main AC one, are self resetting upon removal of fault, and the remaining channel shall continue
to operate. Each channel has independent protective circuitry against short circuit, over-loads and over temperature,
and also has DC protection. Each channel has also LEDs for power-on, signal, clip and protection. Standard power
connectors are used for . Input can be parallel or stereo or bridge and an high quality audio transformerpower outputs
can be added on the input stage of each channel.
Class D technology, switch power, light weight and high power
Illuminated Power Switch
It turns on or off .the unit When the amplifier is powered-on,
the power switch illuminates blue.
3. CONTROL ELEMENTS
3.1 Front Panel
1
1
(Take the rear panel of D4 as an example)

2
5
Protection LED
Red LED, D1, D2, D3, D4 each has four protection functions. They are respectively short-circuit protection, over-
load protection and over heat protection. If one of the protections is activated, the protection LED lights up. If the
unit works well, the protection LED lights off.
4
SIGNAL, CLIP, PROTECTION LED on 2-channel models
SIGNAL, CLIP, PROTECTION LED on 4-channel models
CH 1 CH 2
4
3
CH 1 CH 2 CH 3 CH 4
Gain Control
Turn the gain control clockwise to increase gain and counter clockwise to decrease gain. The maximum voltage
gain for each model is shown on the front panel. The gain control are marked in dB.
5
Gain Control on 2-channel models
5
Gain Control on 4-channel models
5
Clip LED
Red LED, When the signal distortion reaches or surpasses 0.5%, the Led lights up. This means the output level of
signal source is too high and it is time to reduce input level until clip led lights off.
3
3.2 Rear Panel (take the rear panel of D4 as an example)
Power Supply Socket
It is used to connect power cord, after setting the proper voltage, connect one end of power cord with the unit
and another end with mains.
6
24
3
24
324 3
24
3
24
3

6
Combo Input Connector
One connector for each channel. These are combo con-
nectors which input signal to amplifier respectively.
8
Mode Selector
For two-channel models, there is only one mode selector.
It controls the operation of channel1-2. For four-channel
models, there are two model selectors. One controls the
operation of channels1-2. The other controls the operation
of channels3-4. It is impossible to bridge or parallel
channels 1 or 2 with channels 3 or 4.The selectors can
set the amplifier's operating mode for Stereo, Parallel,
or Bridged operation.
- Stereo
In this mode, Channel 1 and Channel 2 operate independently
( just as traditional stereo amplifier). The signal input into
channel 1 can be output from channel 1 only, similarly, the
signal input into channel 2 can be output from channel 2 only.
- Bridged
In this mode, both channels of a pair are combined into
a single channel with twice the output voltage. Use only
the first channel's input and gain control. Set the second
channel's gain control to minimum.
9
- Parallel
In this mode, both inputs of a pair are connected together.
One signal supplies both channels. Please don't connect
different signals to each input. The signal input from
channel 1 or 2 will be output from both channel 1 and 2
simultaneously. Each channel's gain control and speaker
connection are independent.
8
Combo connector of
4-channel models
8
Mode Selector of
2-channel models
9
Breaker
Breaker protects the amplifier from damage from over-current.
If the current surges, the breaker switches off amplifier circuit
automatically, and then it can resume the amplifier operation
by pressing the breaker manually.
7
Combo connector of
2-channel models
6
7
Mode Selector of
4-channel models
10
30Hz FILTER
Set the switch to the position ON, the filter cut off frequency
below 30Hz. This reduces distortion and prevent amplifier
from overload. Set the switch to the position OFF, the switch
is turned off
10

7
10
Fan
The fan can accelerate the flow of air to lower the temperature inside
unit. It runs faster when amplifier temperature gets higher.
12
Note: do not block the air vents of the amplifier. There is a net to
prevent amplifier from dust. Too much dust can block air flow. You
can unscrew the six screw on front panel to take out the net for
cleaning.
Output Connector
There are two kinds of connectors: Binding post and professional speak-on connector. You can choose proper
connectors according to actual need. Wiring connections are shown on the back of the chassis. Please pay
special attention the polarity marks, which are designed to make connections easier. Please refer to PART 4
for wiring.
11
30Hz Filter of 2-channel models 30Hz Filter of 4-channel models
Output connector of 2-channel models Output connector of 4-channel models
10
11 11
12
4. APPLICATION
4.1 Stereo and Parallel Mode
In stereo mode, Channel 1 and Channel 2 operate independentlythe mode selector should be set to STEREO.
( just as traditional stereo amplifier). The signal input into channel 1 can be output from channel 1 only, similarly,
the signal input into channel 2 can be output from channel 2 only.
Connect each loudspeaker with the corresponding channel of the power amplifier as the connection figure shown
on the chassis. Four channel models are shown in the figures below. Make sure the polarity connection of all the
speakers are correct.
Totally two optional modes:
Please see following diagram for connecting the power amplifier into your audio system.

8
4.3 Bridge Mode
In this mode, the signal input into channel 1 will be output from the bridged end, on other hand, the output level
control of channel 2 should be turn down to smallest (turn the volume control at counterclockwise). volumeOnly the
control of channel 1 is used to control the volume of whole system.
connect the binding posts or the speak-on connectors
MODE
set the switch to bridge
+
+
+
+
1+
2+
1+
2+
connect the binding posts or the speak-on connectors
MODE
set the switch to stereo
Channel 4
Channel 3
+ +
+ +
Channel 2
Channel 1
+ +
Channel 2
Channel 1
Channel 4
Channel 3
+ +
connect the binding posts or the speak-on connectors
MODE
set the switch to parallel
Channel 4
Channel 3
+ +
+ +
Channel 2
Channel 1
+ +
Channel 2
Channel 1
Channel 4
Channel 3
+ +
In parallel mode, he signal input from Channel 1 or Channel 2 canthe mode selector should be set to PARALLEL, t
be output from Chanel 1 and Chanel 2 simultaneously. The volume of channel1 or channel 2 can be controlled
separately.
4.2 Parallel Mode

14.8"(376mm) deep
11.2"(285mm) deep
9
5. TECHNICAL SPECIFICATIONS
Indicators (1per channel)
Distortion(AMPTE-IM)
Frequency Response
Damping Factor, at 8 ohms
Output power
Power continuous @0.5% THD . Both channels driven, 230V
8ohms per channel(RMS)
4ohms per channel(RMS)
Power EIAJ@1% THD, both channels driven, 230V
8ohms per channel(EIAJ)
4ohms per channel(EIAJ)
BRIDGED MODE
16ohms (EIAJ)
8ohms (EIAJ)
Load Protection
Power Requirements
Signal to Noise, 20Hz -20KHz
Voltage Gain
Input Sensitivity @ 4ohms
Input Clipping
Input Impedance
D1 D2 D3 D4
2CH Amplifier 4CH Amplifier 2CH Amplifier 4CH Amplifier
2 X 240W
2 X 390W
4 X 240W
4 X 390W
2 X 340W
2 X 540W
4 X 340W
4 X 540W
2 X 270W
2 X 500W
4 X 270W
4 X 500W
2 X 370W
2 X 750W
4 X 370W
4 X 750W
1 X 520W
1 X 1000W
2 X 520W
2 X 1000W
1 X 740W
1 X 1500W
2 X 740W
2 X 1500W
0.5%(THD, DIM, SMPTE)
20Hz-20kHz+/-0.1dB, -3dB points: 10Hz - 60kHz
300 at 8ohms
500
200
105dB/A weighted
40 X (32dB)
1Vrms
10Vrms (+2 )2dB
10k ohms unbalanced, 20k ohms balanced 56(36dB)
Front: AC switch, gain knobs
Power-on: blue
Operation/Protection: red
Clip: red
Rear: low pass filter, mode selector
100
Continuously 7-variable-speed fan, rear- to - front air flow
On/off muting, DC-fault load grounding relay. Internal fault fuses
AC230V,AC115V, 50-60Hz
19"(483mm) rack mounting, 3.5"(88.8mm) tall (2 rack spaces)
11.2"(285mm) deep
5.50Kg 7.90Kg 7.90Kg
5.50Kg
100Hz
Cooling
10KHz
Controls
1KHz
Dimensions
Net Weight
14.8"(376mm) deep

10
6. 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.
3.3 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:
Normal tear and wear.
Instead of operating in accordance with the user's manual thoroughly, any abuse or misuse of this product.
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.
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.

SEKAKU ELECTRON IND. (H.K.) CO., LTD
NO.1, LANE 17, SEC. 2, HAN SHI WEST ROAD, TAICHUNG, 401 TAIWAN
http://www.altoproaudio.com Tel:[phone]
email: [email protected] 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 Sekaku Electron