Thank you for choosing an Adastra UA90 mixer-amplifier as part of your public address system.

This unit is designed to offer high quality, dependable service for mobile and installed systems.

Rack Mounting

The UA series amplifiers can be mounted into a 19” rack cabinet using the supplied rack accessories.

As shown below, the 2 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. CH1 volume control

2. CH2 volume control

3. CH3 volume control

4. LINE 4 volume control

5. AUX volume control

6. MASTER volume control

7. CH1 XLR/Jack input

8. 3.5mm stereo AUX input

9. Power and Audio output indicators

Rear Panel

10. IEC power inlet and fuse holder

11. Power on/off switch

12. 100V and 8Ω speaker output terminals

13. LINE 4 RCA input

14. CH3 6.3mm and screw terminals input

15. CH2 6.3mm and screw terminals input

16. CH1 Phantom-Mic/Line-Vox DIP switches

17. LINE OUT RCA output

18. CH2/CH3 Mic/Line DIP switches

19. CH1 screw terminals input

20. 24V MUTE terminals

Connection and Setup

Set the rear power switch (11) to the “off” position and connect the rear IEC inlet (10) to the mains using the supplied mains lead (or an equivalent approved type). Check that the supply voltage is 170-264Vac 50Hz.

A pair of screw terminals is provided on the right side of the rear panel for connection to an alarm system if required (20). This connection will mute all channels except CH.1 (for alerts) when 24V is present across the terminals. (24V is a standard trigger voltage from most fire and security panels).

Note: Screw terminal blocks can be unplugged from the panel for convenience during connection.

If using a main microphone for paging or announcements, connect this to the CH.1 input on the front panel (7) via either XLR or 6.3mm jack. This may also be a line level (such as CD or mp3) input if required.

Alternatively, the CH.1 mic or line source can be connected on the rear panel via a screw terminal input (19), which is labelled “+ / - / G”.

For Unbalanced connection, connect the signal (core) wire to “+” and connect the Ground (braid) to “- and G”.

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 “G”.

CH.1 has a bank of 3 DIP switches dedicated to it on the rear panel (16) above the terminals.

The right-side DIP switch allows the VOX function to be switched on or off.

When this function is switched on, the input to CH.1 will override the other inputs, causing the volume of any of the other 3 channels to be suppressed when any sound is present on CH.1

When CH.1 is silent, the other 3 channels return to full output volume automatically.

This function is useful for “auto-ducking” background music when making announcements.

The centre of the 3 DIP switches selects between MIC or LINE input. Position this switch depending upon which input source is used, so that the correct channel input level is set for the input type.

The left side DIP switch is labelled “PHANTOM” and switches 24Vdc phantom power to the CH.1 front XLR input for use with paging or condenser microphones that require phantom power.

CH.2 and CH.3 can also accept either microphone or line input, via either 6.3mm jack or screw terminal inputs on the rear panel (14, 15)

The screw terminals for CH.2 and CH.3 are connected in the same way as described above for CH.1

For 6.3mm jack, connection can be Unbalanced (Tip +, Sleeve -/GND) or Balanced (Tip +, Ring -, Sleeve GND)

There are a pair of DIP switches (18) for CH.2 and CH.3 to select MIC or LINE, depending upon the input type. Note: No phantom power or vox override are available on these inputs.

CH.4 is an input for Line level only and is connected via a pair of RCA sockets (13)

Connect the Left and Right output from a CD, mp3, DAB/FM tuner, message machine or other line level source to these sockets using a standard twin RCA/phono lead (L+R are summed to mono).

CH.5 is an auxiliary input connected via a 3.5mm stereo jack on the front panel (8).

This is a line input and can be used for connecting a smart phone, laptop or mp3 player for audio playback.

A twin RCA line output (17) is provided for connecting the mix of all channels onto further amplifiers.

Speaker Connections

The UA series amplifiers can be used either as 100V line amplifiers or standard low impedance power amplifiers. These 2 configurations cannot be used together, so it is important to decide which method will be used at the start.

Operation

When all connections to the amplifier are made, turn all rotary controls down and switch on the power (11)

A power LED will illuminate at the left side of the audio output indicator LEDs (9).

Use either a microphone or a line input signal for checking the system. Turn up the MASTER rotary control (6) part way for testing and increase the rotary control for the channel being used for testing (1-5) until the output is heard through the speakers. Turn up the MASTER to the maximum required volume level and reduce the channel volume control if necessary. Then check each input being used in turn to set the correct level.

Note: If a microphone is being used, point it away from the speakers, making sure that it is not able to “hear” the speakers, which can cause feedback (squealing or howling noise).

When not being used, turn down the MASTER control before powering down to avoid loud clicks or pops.