ART MX821S Eight Channel Mic/Line Mixer

1. Introduction

The ART MX821S is a versatile rack-mount mixer designed to combine eight independent input channels into a stereo line-level output. This unit is suitable for a variety of applications, including live sound, studio recording, and permanent installations in conference rooms, boardrooms, churches, restaurants, and health clubs. Its robust design and comprehensive features ensure reliable long-term operation.

Each input channel on the MX821S accommodates either a balanced XLR microphone input or an unbalanced 1/4-inch TS line-level signal. Independent level and pan controls are provided for each channel, allowing precise mixing and stereo imaging. The mixer also features switchable +48 Volt phantom power for each microphone input. A master level control adjusts the overall signal output to the low-impedance balanced 1/4-inch TRS jacks. For expanded systems, Prefade output (unaffected by the master level control) and Aux Bus input RCA jacks facilitate patching of multiple units.

2. Features

• Eight independent input channels with individual level and pan controls.
• Pan controls allow precise placement of each mono input signal within the stereo output image.
• Balanced XLR microphone inputs or unbalanced 1/4-inch TS line-level inputs on each channel.
• Full +48V low-noise phantom power, individually switchable for each microphone input.
• Master level control for overall output adjustment.
• Prefade output and Aux Bus input RCA jacks for linking multiple units.
• Single high 19-inch rack-mount format for easy installation.
• Built-in power supply for convenience.

3. Setup

3.1 Unpacking and Inspection

Carefully unpack the MX821S mixer and inspect it for any signs of damage that may have occurred during shipping. If damage is found, contact your dealer immediately.

3.2 Rack Mounting

The MX821S is designed for standard 19-inch rack mounting and occupies one rack unit (1U) of space. Secure the unit using appropriate rack screws to ensure stability.

3.3 Power Connection

Connect the supplied AC power cord to the IEC power inlet on the rear panel of the MX821S and then to a suitable electrical outlet. The unit operates on 240 Volts AC. Ensure the power switch on the front panel is in the 'OFF' position before connecting to power.

3.4 Input Connections

Each of the eight input channels features a combination XLR/1/4-inch TS jack on the rear panel. Connect balanced microphones using XLR cables or unbalanced line-level sources (such as instruments or playback devices) using 1/4-inch TS cables. Ensure all connections are secure.

3.5 Output Connections

Connect the main stereo output of the MX821S to your amplifier, powered speakers, or recording interface using balanced 1/4-inch TRS cables. The output jacks are located on the rear panel. For linking multiple units, utilize the Prefade Output and Aux Bus Input RCA jacks as needed.

Figure 1: Front panel of the ART MX821S, showing master and individual channel controls.

Figure 2: Rear panel of the ART MX821S, detailing XLR/TS inputs, TRS outputs, Aux Bus, Prefade, and power connections.

4. Operation

4.1 Powering On

After all connections are made, press the 'POWER' switch on the front panel to turn on the unit. The power indicator LED will illuminate.

4.2 Channel Level and Pan Controls

• Level Knob: Adjusts the input gain for each individual channel. Start with these knobs at their minimum position and gradually increase to achieve the desired signal level without clipping.
• Pan Knob: Positions the signal of each channel within the stereo field of the main output. Turn left for more signal in the left output, right for more in the right output, and center for an equal balance.

4.3 Phantom Power Activation

For condenser microphones requiring +48V phantom power, locate the corresponding phantom power switch for the desired channel on the rear panel (typically a DIP switch or small toggle). Activate phantom power only for microphones that require it and are compatible. Ensure the microphone is connected before activating phantom power to prevent damage.

4.4 Master Level Control

The 'MASTER LEVEL' knob on the front panel controls the overall output volume of the mixed stereo signal. Adjust this control to set the final output level to your connected amplifier or recording device.

4.5 Aux Bus and Prefade Output

The 'AUX BUS IN' RCA jacks allow you to connect the output of another mixer or audio device to expand the number of available inputs. The 'PREFADE OUT' RCA jacks provide a stereo output signal that is independent of the MX821S's master level control, useful for sending a signal to a separate monitoring system or another mixer without affecting the main mix.

5. Maintenance

The ART MX821S is designed for reliable operation with minimal maintenance. Follow these guidelines to ensure longevity:

• Cleaning: Use a soft, dry cloth to clean the exterior of the unit. Avoid abrasive cleaners, solvents, or excessive moisture.
• Ventilation: Ensure adequate airflow around the unit, especially if rack-mounted, to prevent overheating. Do not block ventilation openings.
• Environment: Operate the mixer in a dry environment, away from direct sunlight, extreme temperatures, and sources of vibration.
• Power: Disconnect the unit from the power supply before cleaning or if it will be unused for extended periods.

6. Troubleshooting

If you encounter issues with your ART MX821S, refer to the following common problems and solutions:

• No Sound Output:
  • Check if the unit is powered on and the power LED is illuminated.
  • Verify all input and output cables are securely connected.
  • Ensure individual channel level knobs and the master level knob are turned up.
  • Confirm that the connected amplifier or powered speakers are operational and their volume is set appropriately.
• Humming or Noise:
  • Ensure all audio cables are properly shielded and in good condition.
  • Check for ground loops by ensuring all equipment is connected to the same power circuit or using a ground loop isolator if necessary.
  • Disconnect inputs one by one to identify if a specific source is introducing noise.
  • Verify that phantom power is only enabled for microphones that require it.
• Distorted Audio:
  • Reduce the input level of the offending channel using its level knob.
  • Lower the master level control.
  • Ensure the connected devices (microphones, instruments) are not outputting an excessively hot signal.
• Phantom Power Not Working:
  • Verify that the individual phantom power switch for the channel is engaged.
  • Ensure the microphone cable is an XLR type and is fully connected.

If these steps do not resolve the issue, contact ART customer support for further assistance.

7. Specifications

8. Warranty and Support

8.1 Warranty Information

The ART MX821S is covered by a 3-year manufacturer’s defect warranty. This warranty covers defects in materials and workmanship under normal use. Please retain your proof of purchase for warranty claims. The warranty does not cover damage caused by misuse, accident, unauthorized modification, or improper operation.

8.2 Customer Support

For technical assistance, warranty service, or general inquiries, please contact ART (Applied Research and Technology) customer support. Refer to the official ART website or your product documentation for the most current contact information.