HPA6 - Processor ALTO - Free user manual and instructions

Product Type	6-Channel Stereo Headphone Amplifier
Brand	Alto Professional
Model	HPA6
Dimensions (W x D x H)	483 mm (19 inches) x 200 mm x 44 mm (1U)
Weight	2.8 kg (approx.)
Power Supply	100-240 V AC, 50-60 Hz
Power Consumption	30 W (max)
Number of Channels	6 independent stereo channels
Main Inputs	6 x XLR / TRS 1/4" (6.35 mm) balanced
Auxiliary Inputs	6 x TRS 1/4" stereo
Front Direct Input	1 x TRS 1/4"
Headphone Outputs	6 x TRS 1/4" front + 12 x TRS 1/4" rear (18 outputs total)
Main Outputs	6 x XLR / TRS 1/4" balanced (for daisy chaining)
Minimum Load Impedance per Channel	100 Ω (1 headphone), 200 Ω (2 headphones), 300 Ω (3 headphones)
Frequency Response	20 Hz - 20 kHz (±0.5 dB)
Signal-to-Noise Ratio	> 100 dB
Key Features	6 independent headphone amps, mono/stereo mix, left/right mute, main/aux input balance, LED VU meters, clipping detection
Safety	Protective fuse, grounding via power cord, compliance with OSHA sound exposure limits
Maintenance and Cleaning	Unplug before cleaning; use a soft dry cloth; do not use solvents
Spare Parts and Repairability	Spare fuse (identical type); for other repairs, contact an authorized service center
Included Accessories	Power cord, user guide, safety instructions booklet
Warranty	Standard manufacturer's warranty (refer to booklet)
General Information	19" 1U rack unit; gold-plated connectors; short signal path circuit; robust QS9000 certified construction

Frequently Asked Questions - HPA6 ALTO

How do I connect the HPA6 to my mixing console?

Use the main inputs (XLR or TRS 1/4") on the rear of the device. Connect your console's outputs (e.g., main or aux outputs) to the corresponding inputs. Adjust the input gain on the front panel for optimal level (LED between +6 and +18 dBu).

Can I plug multiple headphones into the same channel?

Yes, each channel has three headphone outputs (one on the front, two on the rear). Observe the minimum cumulative impedance: for one headphone, 100 Ω; for two, 200 Ω each; for three, 300 Ω each.

How do I use the auxiliary input?

Connect an additional source (e.g., aux output of a console) to the auxiliary input of the desired channel. Use the Balance knob to blend the main/auxiliary signal. Turn the balance to the left to hear only the auxiliary.

What should I do if I have no sound?

First check the power (Power LED on). Make sure cables are properly connected and sources are sending signal. Verify that the input gain and output gain are not at minimum. Try switching the mono/stereo mode and the mute switches (Left/Right Mute).

How can I avoid distortion?

Monitor the VU meters: the input LED should stay below the clipping threshold (no continuous illumination of the Clip LED). If the output LED clips, reduce the input gain or the output gain of the corresponding channel.

Can I use very low impedance headphones (e.g., 32 Ω)?

Yes, but the minimum load impedance per channel is 100 Ω if using a single headphone. With a 32 Ω headphone, connect it alone on the channel; the total impedance will be 32 Ω, which is lower than 100 Ω and may cause overload. It is recommended to use headphones of at least 100 Ω for a single output, or to distribute the load (e.g., two 200 Ω headphones).

How do I daisy chain multiple HPA6 units?

Use the main outputs (XLR or TRS) of a first HPA6 to connect to the main inputs of a second. This allows distributing the same mix to more headphones. Adjust levels on each unit appropriately.

What is the required power supply voltage?

The HPA6 operates on a mains power supply of 100 to 240 V AC, 50/60 Hz. Check your country's voltage and use the supplied power cord. If in doubt, consult an electrician.

How do I clean the HPA6?

Unplug the device before cleaning. Use a soft dry cloth to wipe the surface. Never use chemicals, solvents, or abrasive cleaners.

What should I do if the fuse blows?

Unplug the device and replace the fuse with a same type and rating (indicated near the fuse holder). If the problem persists, consult a qualified technician.

USER MANUAL HPA6 ALTO

ALTO PROFESSIONAL

HPA6

USER GUIDE

ENGLISH (2-7)

GUÍA DEL USUARIO

ESPAÑOL (8 - 14)

GUIDE D'UTILISATION

FRANÇAIS (15 - 20)

GUIDA PER L'USO

ITALIANO (21 - 26)

BENUTZERHANDBUCH

DEUTSCH (27 - 32)

GEBRUIKERSHANDLEIDING

NEDERLANDS (33 - 38)

USER GUIDE (ENGLISH)

BOX CONTENTS

• HPA6
• Power Cable
• User Guide

• Safety Instructions & Warranty Information Booklet

• Make sure all items listed in the Box Contents are included in the box.

• READ THE SAFETY INSTRUCTION BOOKLET BEFORE USING THE PRODUCT.
• Switch everything on in the following order:

• audio input sources (i.e. instruments, CD/MP3 players)
- HPA6
- speakers/amps

1. When turning off, always reverse this operation:

2. speakers/amps

3. HPA6
4. last, any input sources

CAUTION! Permanent hearing loss may be caused by exposure to extremely high noise levels. The U.S. Government's Occupational Safety and Health Administration (OSHA) has specified permissible exposures to certain noise levels.

According to OSHA, exposure to high sound pressure levels (SPL) in excess of these limits may result in hearing loss. When using equipment capable of generating high SPL, use hearing protection while such equipment is under operation.

HOURS PER DAY SPL	EXAMPLE
8	90	Small
6	92	Train
4	95	Subway
3 97 High level desktop monitors
2 100 Classical music concert
1.5	102	Riveting machine
1	105	Machine factory
.50	110	Airport
.25 or less	115 Rock concert

gig train

INTRODUCTION

Thanks for purchasing the Alto Professional HPA6! HPA6 is a universal, multi-purpose mixer and headphone amplifier for rehearsal, studio, or stage. Perfect for headphones, in-ear monitors, or personal monitor mixing, HPA6 features six independent high-power stereo amplifiers in one compact rack unit that delivers maximum audio quality, even at very high or very low volume levels; HPA6 has a minimized circuitry path which means there's less "stuff" for your signal to pass through, keeping your sound clear and crisp.

• Manufactured under QS9000 certified quality system
• Six independent high-powered headphone amplifiers in a compact, 1RU size
• Supplies six fully independent mixes for up to 18 pairs of headphones
- Stereo Aux Input on each channel with level adjustments
• Additional Direct Input on front panel to mix in additional sources
• Four-segment LED on each channel for easy visual monitoring
• Mono and Left/Right Mutes per channel for two mono mixes per channel
• High-quality components and exceptionally rugged construction
• Servo-balanced, gold-plated XLR and 1/4" TRS connectors

FRONT PANEL CONTROLS

ALTO POWER MWR CHANNEL 1 CHANNELS CHANNEL 2 CHANNELS CHANNEL 3 CHANNELS CHANNELS CHANNELS POWER HPAG CHANNEL CHANNELS CHANNELS POWER

1. Direct input - Feeds an external audio source directly into the main signal path.
2. Input gain control - Controls the signal level going to the Main or Direct Inputs.
3. Input level meter - Displays the signal level coming from Main/Direct Inputs. For the best quality of input signal, the LED should range from +6 to +18 dBu. If the Clip LED (in the Output Level Meter) is always on, reduce the input level using the input gain control.
4. Aux input - Provides a separate stereo input signal which can be mixed with the Main/Direct Input signal.
5. L mute switch - Mutes the left input signal.
6. R mute switch - Mutes the right input signal.
7. Mode switch - Switches the operational mode between mono and stereo.
8. Mono LED - This LED lights up when the unit is in mono mode. When the LED is off, the unit is in stereo mode.
9. Headphone output - 1/4" TRS phone jack used to output the signal of the individual channel. There are also 12 additional headphone outputs (two for each channel) on the rear panel.
10. Balance control - Sets the amount of the signal coming from Aux Input and Main/Direct Input. When the Aux Input is not in use, it will regulate the stereo imaging of the input signal. When a signal is fed into the Aux Input, the balance control will regulate the ratio of the Main Input (or Direct In) and the Aux Input signals.
11. Output gain control - Adjusts the output level of the individual channel.
12. Output level meter - Displays the output signal level. If the Clip LED lights up, turn down the input gain control and/or the individual output gain control to avoid distortion.

REAR PANEL CONTROLS

13 14 ALTO 15 16 17

1. Fuse holder - If the fuse blows, replace it with a fuse of the same type.
2. Power Connector - Use the included power cable to connect this connector to a power source. Please check the voltage accepted by the unit and the voltage available from your power source before connecting it.
3. Main input connectors - Balanced 1/4" TRS and XLR connectors used to input the stereo signal.
4. Main output connectors - Balanced 1/4" TRS and XLR connectors used to output the main signal. Use these connectors to link several headphone amplifiers together.
5. Headphone out (1-12) - These are 12 additional headphone outputs (two for every channel) wired in parallel with the output available on the front panel.

APPLICATIONS

USING THE MAIN INPUT CONNECTORS

1. Connect your source to the rear panel Main Input connectors on HPA6.
2. Set the Input Gain (Main section) and the Balance control (Channel section) on center position. Set the Output gain of each channel all the way down.
3. Check the input level meter for optimal signal.
4. Connect headphones to HPA6 and start to raise the output gain of each channel to the desired listening volume.

ALTO HPA6 POWER Main Outputs

USING THE AUX INPUTS

You can also play back a signal to feed in a vocal microphone and then connect a mixer's aux send to HPA6's Aux Input. Use the Balance control to give the vocalist the desired mix between the voice and the playback signal. Then, adjust the Output Gain control to regulate the overall desired volume.

graph TD
    A["ALTO"] --> B["Main Out"]
    B --> C["Aux Send"]
    C --> D["HPA6"]
    style A fill:#f9f,stroke:#333
    style D fill:#ccf,stroke:#333

Through the Aux Inputs, you can use the six channels of HPA6 independently to give individual mixes to six different musicians. Connect the Aux Sends or Subgroup outputs directly to the Aux Input of HPA6. Then rotate the Balance control on your HPA6 fully to the left. This will route only the AUX IN signal to the headphones.

graph TD
    A["ALTO"] --> B["AUX Send 1"]
    A --> C["AUX Send 2"]
    A --> D["AUX Send 3"]
    A --> E["AUX Send 4"]
    A --> F["AUX Send 5"]
    A --> G["AUX Send 6"]
    H["HPA6"] --> B
    H --> C
    H --> D
    H --> E
    H --> F
    H --> G
    B --> I["Output: ALTO, HPA6"]
    C --> J["Output: ALTO, HPA6"]
    D --> K["Output: ALTO, HPA6"]
    E --> L["Output: ALTO, HPA6"]
    F --> M["Output: ALTO, HPA6"]

USING MULTIPLE HEADPHONES ON THE SAME CHANNEL

Each channel provides three headphone outputs. These jacks are all connected in parallel. For best results, please note the impedance information:

• When connecting one headphone to each channel, the minimum impedance of the headphone should be 100 ohms.
• When connecting two headphones to each channel, the minimum impedance of each headphone should be 200 ohms.
• When connecting three headphones to each channel, the minimum impedance of each headphone should be 300 ohms.

INSTALLATION AND CONNECTION

Read the following section carefully. Not paying attention to the input signal level, to the routing of the signal and to the assignment of the signal will result in unwanted distortion, a corrupted signal or no sound at all.

Power Connection

Use the same fuse as marked on the fuse holder near the power connector. Connect HPA6 to a standard power outlet using the enclosed power cable.

Audio Connection

The HPA6 uses balanced XLR and 1/4" TRS phones jack. It can be connected to other units in a variety of ways to support a vast range of applications without experiencing a signal loss.

Wiring Configuration

XLR servo connectors can be wired in balanced and unbalanced modes. Please wire your systems according to the following examples:

• 1/4" Phone jack

TS Type Unbalanced

Ring Tip Sleeve

TRS Type Balanced

Ring Tip Sleeve

TRS Type Unbalanced

• XLR connector
  

Simple line drawing of a plug with three pins and a curved arrow pointing to one pin (no text or symbols)

Pin1 (±)

Pin2 (+)

Pin3 (-)

(Linked to Pin1 manually

XLR Type Unbalanced

Pin3 (-) Pin2 (+)

Pin1 (m)
XLR Type Balanced

• Balanced

Tip Ring Sleeve Sleeve Ring Tip

Tip Ring Sleeve

Tip Ring Sleeve 1 2 3 Tip Ring Sleeve

• Unbalanced
  

Tip Ring Sleeve Tip Sleeve Tip Sleeve Sleeve Tip Tip Ring Sleeve Sleeve Ring Tip Tip Sleeve Tip Ring Sleeve

graph TD
    subgraph Top
        A1["Tip"] --> B1["Ring"]
        A1 --> C1["Sleeve"]
        A2["Tip"] --> B2["Ring"]
        A2 --> C2["Sleeve"]
        A3["Tip"] --> B3["Ring"]
        A3 --> C3["Sleeve"]
        A4["Tip"] --> B4["Ring"]
        A4 --> C4["Sleeve"]
        A5["Tip"] --> B5["Ring"]
        A5 --> C5["Sleeve"]
        A6["1"] --> B6["Center"]
        A7["2"] --> B7["Screen"]
        A8["3"] --> B8["Screen"]
    end
    subgraph Bottom
        B1 --> C1
        B1 --> C2
        B1 --> C3
        B2 --> C4
        B2 --> C5
        B3 --> C6["Center"]
        B3 --> C7["Screen"]
        B4 --> C8["Center"]
        B4 --> C9["Screen"]
        B5 --> C10["Center"]
        B5 --> C11["Screen"]
        B6 --> C12["Center"]
        B6 --> C13["Screen"]
        B7 --> C14["Center"]
        B7 --> C15["Screen"]
        B8 --> C16["Center"]
        B8 --> C17["Screen"]
        B9 --> C18["Center"]
        B9 --> C19["Screen"]
        B10 --> C20["Center"]
        B10 --> C21["Screen"]
        B11 --> C22["Center"]
        B11 --> C23["Screen"]
        B12 --> C24["Center"]
        B12 --> C25["Screen"]
        B13 --> C26["Center"]
        B13 --> C27["Screen"]
        B14 --> C28["Center"]
        B14 --> C29["Screen"]
        B15 --> C30["Center"]
        B15 --> C31["Screen"]
        B16 --> C32["Center"]
        B16 --> C33["Screen"]
        B17 --> C34["Center"]
        B17 --> C35["Screen"]
        B18 --> C36["Center"]
        B18 --> C37["Screen"]
        B19 --> C38["Center"]
        B19 --> C39["Screen"]
        B20 --> C40["Center"]
        B20 --> C41["Screen"]

GUÍA DEL USUARIO (ESPAÑOL)

CONTENIDO DE LA CAJA

Punta Manguito

Tipo TS no balanceado

Nuca Punta Manguito

Tipo TRS balanceado

Nuca Punta Manguito

Bague Pointe manchon

Type TRS symétrique

Bague Pointe manchon

Simple line drawing of a plug with three pins and a curved arrow indicating a pin (no text or symbols)

Broche 1 (±)

Broche 2 (+)

Broche 3 (-)

Simple line drawing of a multi-pin electrical connector (no text or symbols)

Broche 1 (m)

Broche 2 (+)

Pointe bague manchon Manchon bague pointe Pointe bague manchon

Pointe Bague Manchon 1 2 3 Pointe Bague Manchon

• Asymétrique
  

Pointe bague manchon Pointe manchon Pointe manchon Manchon pointe Pointe bague manchon Manchon bague pointe Pointe manchon Pointe bague manchon

graph TD
    subgraph Top
        A["Pointe"] --> B["Bague"]
        B --> C["Manchon"]
        C --> D["Pointe"]
        D --> E["Manchon"]
        E --> F["1"]
        F --> G["2"]
        G --> H["3"]
        H --> I["1"]
        I --> J["2"]
        J --> K["3"]
    end
    subgraph Bottom
        L["Pointe"] --> M["Manchon"]
        M --> N["Pointe"]
        N --> O["Bague"]
        O --> P["Manchon"]
        P --> Q["Pointe"]
        Q --> R["Manchon"]
        R --> S["1"]
        S --> T["2"]
        T --> U["3"]
        U --> V["1"]
        V --> W["2"]
        W --> X["3"]
        X --> Y["Centre"]
        Z["Masse"] --> AA["Centre"]
    end

ALTO HPA6 MAIN Uscite

IMPIEGO DEGLI INGRESSI AUX

Simple line drawing of a plug with three pins and a curved connector (no text or symbols)

Pin1 (m)

Pin2 (+)

Pin3 (-)

Pure electrical circuit lines without any symbols

Spitze Ring Manschette
Manschette Ring Spitze

Pure electrical connector diagram without any text or symbols

Pure electrical circuit lines without any symbols

Spitze Ring Manschette

Spitze

Ring

Manschette

Spitze

Ring

Manschette

• Unsymmetrisch
  

Spitze Ring Manschette Spitze Manschette Spitze Manschette Manschette Spitze Spitze Ring Manschette Manschette Ring Spitze Spitze Manschette Spitze Ring Manschette

graph TD
    A["Spitze"] --> B["Ring"]
    B --> C["Manschette"]
    C --> D["Spitze"]
    D --> E["Manschette"]
    E --> F["Spitze"]
    F --> G["Ring"]
    G --> H["Manschette"]
    H --> I["Spitze"]
    I --> J["Manschette"]
    J --> K["Spitze"]
    K --> L["Ring"]
    L --> M["Manschette"]
    M --> N["Spitze"]
    N --> O["Manschette"]
    O --> P["Spitze"]
    P --> Q["Manschette"]
    Q --> R["Spitze"]
    R --> S["Manschette"]
    S --> T["Spitze"]
    T --> U["Manschette"]
    U --> V["Spitze"]
    V --> W["Manschette"]
    W --> X["Spitze"]
    X --> Y["Manschette"]
    Y --> Z["Spitze"]
    Z --> AA["Manschette"]
    AA --> AB["Spitze"]
    AB --> AC["Manschette"]
    AC --> AD["Spitze"]
    AD --> AE["Manschette"]
    AE --> AF["Spitze"]
    AF --> AG["Manschette"]
    AG --> AH["Spitze"]
    AH --> AI["Manschette"]
    AI --> AJ["Spitze"]
    AJ --> AK["Manschette"]

GERBRUIKERSHANDLEIDING (NEDERLANDS)

INHOUD VAN DE DOOS

Connectors: XLR and 1/4"

Type: Electronically servo-balanced, RF-filtered

Impedance:

• Balanced : > 50 KΩ
• Unbalanced: > 25 KΩ

Max. Input Level: +21 dBu typical, balanced or unbalanced

AUX IN and DIRECT IN

Connectors: 1/4" TRS (tip=left, ring=right, sleeve=ground)

Impedance:

Unbalanced: > 25 KΩ

Max input level: +21 dBu, unbalanced

OUTPUT

Connectors: XLR and 1/4"

Type: balanced/unbalanced

Max. output level: +21 dBu balanced and unbalanced

PERFORMANCE

• Frequency response: 10 Hz to 50 kHz,+0/-3 dB
• Signal-to-Noise Ratio: >90 dB, unweighted
• Signal-to-Noise: Ref: +4 dBu, 22 Hz - 22 kHz
• THD: Ref: +4 dBu, 0.005%

POWER AMPLIFIER

• Max output power: +21 dBmW
• Min. output impedance: 100 Ω
- Max gain: +20 dB

POWER SUPPLY

Power Consumption: 14 watts

Power Supply: AC 120V, 60Hz

AC 230V - 240V, 50 Hz

Power connection: Standard IEC

DIMENSIONS

(W x D x H) 19" x 8.54" x 1.7"; 483 mm x 217 mm x 44 mm

WEIGHT

6.39 lbs.; 2.9 kg

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