4
1. INTRODUCTION
Thank you very much for expressing your confidence in
LTO products by purchasing our HPA4 4-Channel Head-
phone 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
Excluding 1 knob control, 1 jack and 8 LEDs for the common main section, the
LTO HPA4 4-Channel Headphone
3. CONTROL ELEMENTS
1
2
4
3
5
6
LTO
INPUT LEVEL(dBu)
DIRECT IN
INPUT GAIN
OUTPUT LEVEL(dBu)
MUTE
R
L
3
MONO
2
4
5
6
1
0
0
15
15
CHANNEL 1
BASS
HEADPHONE OUT
TREBLE
OUTPUT GAIN
0
AUX IN
15
15
2
4
5
6
1
0
3
MAIN SECTION
MUTE
AUX
BALANCE
MAIN IN
0
12
CLIP
18
12
6
6
0
CLIP
18
12
6
6
18
12
18
R
9
7
8
11
10
12
13
14
3.1 The ront
anel
F
P
Amplifier also contains 3 Push-button switches, 2 knob controls, 2 phone jacks and 4 LEDs for each individual channel.
LTO
INPUT LEVEL(dBu)
DIRECT IN
INPUT GAIN
OUTPUT LEVEL(dBu)
MUTE
R
L
3
MONO
2
4
5
6
1
0
4-Channel
HEADPHONE
AMPLIFIER
HPA4
0
15
15
CHANNEL 1
BASS
HEADPHONE OUT
TREBLE
OUTPUT GAIN
0
AUX IN
15
15
2
4
5
6
1
0
3
0
12
CLIP
OUTPUT LEVEL(dBu)
18
12
6
6
MUTE
R
L
MONO
AUX
BALANCE
OUTPUT GAIN
2
4
5
6
1
0
0
15
15
BASS
HEADPHONE OUT
TREBLE
0
AUX IN
15
15
0
12
CLIP
OUTPUT LEVEL(dBu)
18
12
6
6
MUTE
R
L
MONO
AUX
BALANCE
OUTPUT GAIN
2
4
5
6
1
0
3
MAIN SECTION
0
15
15
BASS
HEADPHONE OUT
TREBLE
0
AUX IN
15
15
0
12
CLIP
OUTPUT LEVEL(dBu)
18
12
6
6
MUTE
R
L
MONO
0
15
15
BASS
HEADPHONE OUT
TREBLE
0
AUX IN
15
15
AUX
BALANCE
OUTPUT GAIN
2
4
5
6
1
0
3
CHANNEL 2
CHANNEL 3
CHANNEL 4
ON
OFF
POWER
MUTE
MUTE
MUTE
MUTE
MAIN IN
MAIN IN
MAIN IN
AUX
BALANCE
MAIN IN
3
0
12
CLIP
18
12
6
6
0
CLIP
18
12
6
6
18
18
18
12
18
18
R
