Alto Professional HPA4 user manual
User's Manual
HPA4
4-Channel HEADPHONE AMPLIFIER
R
LTO
www.altoproaudio.com
Version 2.0 February 2003
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.
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.
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.
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.
CAUTION
Describes precautions that should be observed to
prevent damage to the product.
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.
Fuse
To prevent fire and damage to the product, use only
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
Dear Customer:
Thanks for choosing LTO HPA4 4-Channel Headphone Amplifier and thanks for choosing the one of 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 line presents unparalleled analogue and digital products made by Musicians for Musicians in our R&DLTO
Centres 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 our job, we'd like to share with you our work and our dreams, pay attention to your suggestions and your
comments.
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.
Our HPA4 4-Channel Headphone Amplifier is the result of many hours of listening and tests involving commonLTO
people, area experts, musicians and technicians.
The result of this effort is a versatile Headphone Amplifier featuring 4 separated channels, each channel provides
3 push-button switches, 4 knob controls, 2 phone jacks and 8 digit output level meters. The common main section
contains 1knob control, 1 jack and 8 digit input level meters.
Nothing else to add, but herewith we would like to thank all the people that made the LTO HPA4 4-Channel
Headphone Amplifier a reality available to you, and thank our designers and all the LTO staff, who make possible
the realization of products containing our idea of music and sound and there to
best way, and are conscious that you are our best richness.
Thank you very much.
LTO AUDIO TEAM
support you, our customers, in the
2
TABLE OF CONTENTS
1. INTRODUCTION.....................................................................................................................................4
2. FEATURE LIST ......................................................................................................................................4
3. CONTROL ELEMENTS .........................................................................................................................4
3.1 The Front Panel
3.2 The Rear Panel
4. INSTALLATION & CONNECTION ........................................................................................................7
4.1 Mains Connection
4.2 Audio Connection
a. Wiring Configuration
b. In Line Connection
4.3 Rack Mounting
5. APPLICATION.........................................................................................................................................8
5.1 Use the HPA4 as a Headphone Amplifier
5.2 Use the HPA4 as Independent Power Amplifiers
5.3 The HPA4 in Studio Application
5.4 The HPA4 in Mono/Stereo Application
6. TECHNICAL SPECIFICATIONS ...........................................................................................................11
7.WARRANTY ..........................................................................................................................................12
3
1. INTRODUCTION
Thank you very much for expressing your confidence in LTO products by purchasing our HPA4 4-Channel Headphone Amplifier. With the HPA4 you have acquired an extremely musical and flexible 4-Channel Headphone Amplifier.
Featuring four stereo headphone amplifiers, the LTO HPA4 4-Channel Headphone Amplifier performs a number of
necessary tasks, not all of which are headphone related.
The HPA4 4-Channel Headphone Amplifier provides Main Inputs on the rear panel and Direct In Input on the front
panel to drive any or all of the 4 stereo headphone amplifiers, when using the Direct In Input, the Main Inputs signal
will be interrupted automatically, the Main Outputs on the rear panel can be used to interlink any number of HPA4s
for expanding. The AUX In input on each channel is used to add an additional input signal to the master signal, with
the corresponding Balanced Control to determine the mix ratio between the two signals.
In parallel with the Headphone Outputs on the rear panel, the Headphone Output on the front panel is also used to
output the signal of the individual channel.
2. FEATURE LIST
Signal Rack Unit
4 individual channels
Common input gain control, and individual output gain control
Up to 3 headphone outputs per channel
Direct In and Headphone Output on the front panel for easy operation, esp. used in the rack mounting application
Input and Output Level Meter
Balance Control to mix up the Main In and the Aux In signal
Main Outputs for chaining further HPA4 headphone amplifiers
Maximum audio quality even at high volume levels
Exceptionally rugged construction ensures long life and durability
Universal and professional headphone amplification system for studio and stage application
Manufactured under QS9000 certified quality system
3. CONTROL ELEMENTS
INPUTLEVEL(dBu)
6 18181812 18 18
18
6
0
12
DIRECTIN
MAINSECTION
24
1
0
INPUTGAIN
LTO
R
Excluding 1 knob control, 1 jack and 8 LEDs for the common main section, the LTO HPA4 4-Channel Headphone
Amplifier also contains 3 Push-button switches, 2 knob controls, 2 phone jacks and 4 LEDs for each individual channel.
OUTPUTLEVEL(dBu)
6
18
0
6
CLIP
12
MUTE
MUTE MUTE MUTE MUTE
L
3
5
6
R
1
AUX
MAININ
BALANCE
12
CLIP
MONO
3
24
5
6
0
OUTPUTGAIN
0
15
15
15
BASS
TREBLE
HEADPHONEOUT
AUXIN
CHANNEL1
OUTPUTLEVEL(dBu)
0
15
6
18
0
6
12
MUTE
RLMONO
1
AUX
MAININ MAININ MAININ
BALANCE OUTPUTGAIN
12
CLIP
3
24
5
6
0
0
15
15
15
BASS
TREBLE
HEADPHONEOUT
AUXIN
CHANNEL2 CHANNEL3 CHANNEL4
0
15
OUTPUTLEVEL(dBu)
12
6
18
0
6
12
MUTE
RLMONO
24
1
AUX
0
BALANCE OUTPUTGAIN
CLIP
15
3
TREBLE
AUXIN
5
6
0
15
OUTPUTLEVEL(dBu)
12
6
18
0
6
12
MUTE
RLMONO
24
1
AUX
0
BALANCE OUTPUTGAIN
0
CLIP
3
5
6
0
15
15
15
15
BASS
TREBLE
HEADPHONEOUT
AUXIN
POWER
ON
OFF
0
15
15
BASS
HEADPHONEOUT
3.1 The ront anelFP
5
12 13 14
OUTPUT LEVEL(dBu)
18
0
MUTE
MAIN IN
BALANCE
10
6
12
MUTE
L
AUX
8
CLIP
3
5
6
6
12
6
CLIP
MONO
R
3
24
1
6
0
OUTPUT GAIN
11
7
0
0
15
15
BASS
HEADPHONE OUT
9
15
15
TREBLE
AUX IN
5
CHANNEL 1
4
LTO
3
INPUT LEVEL(dBu)
6 1812 18
18
6
0
12
DIRECT IN
1
1
MAIN SECTION
24
0
INPUT GAIN
2
R
HPA4
4-Channel
HEADPHONE
AMPLIFIER
4
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