Adastra US-series Compact 100V Slave Amplifiers

Introduction

Thank you for choosing an Adastra US-series slave amplifier as part of your public address system. This unit is designed to offer high quality, dependable service for mobile and installed systems. Please read this manual to gain the best results from your product and avoid damage through misuse.

Safety Symbol and Message Conventions

Safety Notice

1. Prior to use, read through this manual.
2. Keep the manual in good condition.
3. Pay attention to safety warnings.
4. Observe all operating requirements.
5. Do not use the device near water or wet areas.
6. For cleaning, only use a lint-free, dry cloth.
7. Install according to the specifications.
8. Place away from heat sources or heating appliances.
9. Use the mains lead provided and avoid damage to the cable or connectors.
10. Unplug power from mains during stormy weather or if unused for long periods.
11. In case of malfunction, water ingress, or other damage, consult qualified service personnel.
12. Do not place in damp areas or near liquids or moisture. Do not spill liquids on the housing.
13. Please pay attention to warning symbols during transit and placement.
14. Terminals marked with the [Hazardous Live] symbol are HAZARDOUS LIVE and should only be connected by qualified personnel.
15. Ensure that the apparatus is connected to a mains socket with a protective [Earth] connection.
16. Ensure correct operation of the mains switch.

Warning

To prevent the risk of fire or electric shock, do not expose any components to rain or moisture. If liquids are spilled on the casing, stop using immediately, allow the unit to dry out, and have it checked by qualified personnel before further use. Avoid impact, extreme pressure, or heavy vibration to the case.

No user serviceable parts inside – Do not open the case – refer all servicing to qualified service personnel.

Safety

• Check for correct mains voltage and condition of the IEC lead before connecting to a power outlet.
• Use double insulated speaker wire with adequate current rating for [100V] speaker connections.
• Only use one type of output (i.e., [8 Ohm] or [100V]) – do not mix or combine these outputs on a single zone.
• Do not connect [8 Ohm] speakers to the [100V] terminal or [100V] speakers to the [8 Ohm] terminal.
• The US-series amplifiers also have a [100V] input for extracting a line input from an existing [100V] speaker feed (this is an input connection and not an additional speaker output).

Placement

• Keep out of direct sunlight and away from heat sources.
• Keep away from damp or dusty environments.
• For rack-mounting, use the supplied accessories and ensure adequate support.
• Ensure adequate airflow and do not cover cooling vents at the front and rear of the amplifier.
• Ensure adequate access to controls and connections.

Cleaning

• Use a soft cloth with a neutral detergent to clean the casing as required.
• Use a vacuum cleaner to clear ventilation grilles of any dust or debris build-ups.
• Do not use strong solvents for cleaning the unit.

Mounting Options

Rack mounting

The US series amplifiers can be mounted into a 19" rack cabinet using the supplied rack accessories. The two joining brackets link a pair of UM series amplifiers together to form a full-width 1U rack-mount pair. One rack ear can be mounted at each end for fixing to the rack strip.

Wall or under counter mounting

The rack mounting accessories can also be attached so that the amplifier can be mounted against a wall or under a counter or work surface. To do this, mount the rack ears with the tabs aligned with the top of the housing to provide mounting holes to screw the amplifier to the underside of a work surface or against a wall with the controls visible vertically.

Front Panel

1. MASTER volume control
2. Power & Audio Output indicators

Rear Panel

1. IEC power inlet and fuse holder
2. Power on/off switch
3. [100V] and [8 Ohm] speaker output terminals
4. [Line In] [RCA] input
5. CH3 [6.3mm jack] and screw terminals input
6. CH2 [6.3mm jack] and screw terminals input
7. CH1 Phantom-Mic/Line-Vox [DIP switches]
8. [Line Out] [RCA] output

Connection and Setup

Set the rear power switch (4) to the "off" position and connect the rear IEC inlet (3) to the mains using the supplied mains lead (or an equivalent approved type). Check that the supply voltage is 170-264Vac 50Hz.

The US series slave amplifiers are designed to accept a single line level audio input, such as the line output of a mixer or another amplifier, as a means of expanding an existing sound system. The line input can also be from a [CD player], [MP3 player], [DAB/FM tuner] or other line level source if that is the only audio source that is required.

Input Connection Details

Input connection is via Left + Right [RCA] sockets (7), which are summed to mono for the output, or via a screw terminal input (8), which is labelled "[+] / [-] / [Ground]".

• For Unbalanced connection, connect the signal (core) wire to "[+]" and connect the Ground (braid) to "[-] and [Ground]".
• For Balanced connection, there will be 2 core wires. Connect the hot (usually red) wire to "[+]" and the cold (white, black or blue) wire to "[-]". Then connect the Ground (braid) separately to "[Ground]".

Another input method is provided via the [100V] input terminals (9). This is a pair of screw terminals (+/-) for connecting to the speaker line in a [100V] line system. Connect "[+]" to [100V] and "[-]" to 0V or [Ground] as you would any [100V] speaker. (There is internal protection to ensure that the high voltage cannot cause damage to this input).

Caution: Do not connect [100V] speaker output from this amplifier to its own [100V] input!

This type of input means that an existing [100V] sound system can be extended from any point along its output wiring without the need for running additional signal cables and can also avoid problems associated with signal degradation along low voltage audio cables.

Caution: Do not connect [100V] speaker level to any other input - this could damage the amplifier.

A twin [RCA] line output (6) is provided for connecting the mix of all channels onto further amplifiers.

Speaker Connections

The US series amplifiers can be used either as [100V] line amplifiers or standard low impedance power amplifiers. These two configurations cannot be used together, so decide which method will be used at the start.

100V line systems

For [100V] line systems, connect the amplifier to the first speaker in the system using double-insulated speaker wire which has adequate current rating to handle the total output of the amplifier. Connect the "[100V]" output terminal to the positive (+) connection of the speaker and "[Common]" output to the negative (-) connection of the speaker (14). Connect further speakers in parallel to the first speaker with all positive terminals connected together and all negative terminals connected together.

A [100V] line speaker system can comprise of many speakers connected together. The determining factor for how many speakers can be used on a single amplifier is the power rating. For most purposes, it is advised to connect as many speakers as needed with a combined wattage of no more than 90% of the amplifier's output power rating.

The terminals of a [100V] speaker are connected to a transformer and in some cases, this transformer may be "tapped" for different power ratings. These tappings can be used to adjust the wattage (and output volume) of each speaker in the system to help achieve the ideal total power of the system for the amplifier.

Low impedance systems

The US-series amplifiers can alternatively provide an output for a single [8 Ohm] speaker by connecting the "[8 Ohm]" output to the positive (+) speaker connection and "[Common]" output to the negative (-) speaker connection. It is important to ensure that the speaker load is no lower than [8 Ohm] and that the power handling of the speaker is equal to or greater than the output power of the amplifier.

Operation

1. When all connections to the amplifier are made, turn the MASTER volume control down (1) and switch on the power (4). A power LED will illuminate at the left side of the audio output indicator LEDs (2).
2. Play an input signal (line or [100V]) into the amplifier to check the system. Turn up the MASTER volume control (1) gradually until the output is heard through the speakers. The MASTER acts as the overall volume control.
3. When not being used, turn down the MASTER control before powering down to avoid loud clicks or pops.

Specifications

Disposal

[WEEE symbol] The "Crossed Wheelie Bin" symbol on the product means that the product is classed as Electrical or Electronic equipment and should not be disposed of with other household or commercial waste at the end of its useful life. The goods must be disposed of according to your local council guidelines.

Company Information

Errors and omissions excepted. Copyright© 2021.

AVSL Group Ltd. Unit 2-4 Bridgewater Park, Taylor Rd. Manchester. M41 7JQ

AVSL (EUROPE) Ltd, Unit 3D North Point House, North Point Business Park, New Mallow Road, Cork, Ireland.