Electro-Voice MA-1206/MA-1212 Professional Mixer/Amplifiers

Description and Features

The Electro-Voice MA series of mixer-amplifiers are available with output power ratings of 60 (MA-1206) or 120 (MA-1212) watts. These products are designed to provide background music and facilitate paging in environments such as churches, small businesses, and professional offices.

Key features include:

• Level controls for each input and a master volume control.
• Individual bass and treble tone controls.
• Automatic muting circuit with adjustable threshold.
• 600 ohm transformer-isolated line input for paging, with automatic muting of other inputs.
• Low distortion and output protection circuitry.
• Auxiliary line level inputs with internal mixing for stereo sources.
• Balanced line level output.
• An insertion point between the preamplifier and amplifier stages.
• Phantom power on all microphone inputs, enabling the use of microphones without separate power supplies.

Installation

To prevent hum in the output, ensure all input cables are physically separated from power wiring and transformers. Speaker cables should also be kept away from input and power cables.

Grounding

Ground the chassis of the unit using the ground terminal located on the back panel. For optimal grounding, connect the amplifier to an earth ground, such as a cold water pipe or ground rod. If other equipment is installed, ensure their chassis are connected together to reduce noise and hum.

Ventilation

Provide ample ventilation around the unit to dissipate heat generated by the power amplifier. Avoid blocking or impeding the vent slots. Locate the unit away from direct sunlight, humidity, dust, and vibration.

Key Input Connections

Microphone inputs are designed for balanced Low Impedance (approx. 200 ohms) or unbalanced high impedance (approx. 20k ohms) microphones. For high impedance microphones, use the shortest possible cables to avoid high-frequency loss. A limit of 30 feet is recommended. Microphone inputs can be accessed via XLR connectors or 1/4" phone plugs.

Connections

Typical Connections

Figure 1 illustrates typical connections for the Electro-Voice MA-1206/MA-1212 mixer/amplifiers. It shows how various audio sources like CD players, AM/FM tuners, cassette recorders, and microphones (with stands) can be connected to the input channels. Output connections are shown for speakers, horn speakers, and sound columns. The diagram also indicates connections for mains power, a 24V battery backup, an optional equalizer, and an external power amplifier. A 'VOICE PRIORITY' contact point is also depicted.

Input Connections

Figure 2 details wiring configurations for microphone inputs. It shows how balanced and unbalanced microphones can be connected using either a 3-pin XLR plug or a 1/4-inch (phone) jack. Different jack types, including stereo and mono, are illustrated for unbalanced connections.

Phantom Power: Phantom power allows the use of microphones without separate power supplies on the Mic inputs. When phantom power is active, 24V DC is supplied to pins 2 and 3 of the Mic inputs. To enable phantom power, move the selector switch to the 24V position above the desired input connector.

Microphone Auto Muting Input: When a microphone or other source is connected to Input 1 and the front panel mute switch is on, advance the threshold control until typical voice, not ambient noise, triggers the mute circuit. The microphone's on/off switch can be used, with voice announcements triggering the mute. To disable this function, place the mute switch in the off (defeat) position.

Auxiliary 1 and 2: High-level unbalanced sources can be connected to the Aux 1 and 2 jacks on the back panel. Suitable sources include tape players, CD players, AM/FM tuners, mixer-preamplifiers, or wireless microphones. Use a single-conductor shielded cable. Turntables typically have a separate ground wire; connect this to the ground terminal on the back panel to minimize hum.

The RCA jacks (R and L) for AUX 1 and 2 are designed to match stereo sources. They are internally mixed. Monaural high-level unbalanced sources can be plugged into either the R or L jacks.

Paging: A voice paging signal from a 600 ohm balanced audio paging line (e.g., a PBX system) can be connected to the aux paging input on the back panel.

Power Amp In: This jack provides direct access to the power amplifier. It requires a line-level signal via an RCA plug wired with a single-conductor shielded cable.

Output Connections

The amplifier supports both Low Impedance and high impedance constant-voltage speaker loads (25, 70.7, and 100 volt lines). Key considerations for speaker connections include:

1. Matching Speaker Impedance: Power amplifiers deliver rated power into a rated load impedance. Lower impedances reduce maximum available power and can trigger protection fuses. Avoid significantly lower impedances.
2. Power Loss in Speaker Wire: Speaker wire impedance ideally should be zero. Longer or thinner wires increase impedance, leading to power loss. Table 1 provides permissible copper wire lengths for various wire sizes and speaker impedances to limit loss to 0.5 dB. Doubling wire lengths halves the permissible dB loss. High load impedances allow longer, smaller gauge wiring.
3. Balancing Speaker Levels: Balancing levels among multiple speakers in a low impedance setup is challenging. Constant-voltage high impedance systems simplify this using speakers with transformer taps marked in watts.

Low Impedance Speakers: The low impedance ohm output terminal is for direct connection of one or more standard low impedance speaker systems. For example, connect a single speaker to the common and 4 ohm terminals. Connecting multiple low impedance speakers requires adherence to series and parallel impedance summation rules.

High Impedance/Constant-Voltage Systems: These systems allow for smaller diameter wire for a given power loss. Transformers at speaker locations increase impedance to the desired value. Multiple transformer taps (marked in watts) allow easy adjustment of individual speaker levels. Connect transformer primaries in parallel. For proper operation, all speakers must have the same voltage rating (25, 70.7, or 100 volts). The total power tap rating should be equal to or less than the amplifier's rated output power. Avoid power totals exceeding the rated amplifier power, as this drops the total load impedance below the amplifier's rated load.

Preamp Out: This jack provides a line-level mix of input signals via a 1/4 inch phone plug. It can feed an external equalizer or signal processor whose output would connect to the Power Amp In jack. Using the Preamp Out interrupts the signal to the internal power amplifier.

The balanced line level XLR output connector is suitable for feeding external recording devices or assistive listening systems. When the rear panel switch is in the "fixed" position, the master volume control does not affect this output level, allowing independent setting of recorder input levels. The tape output is buffered.

Operation

Front Panel Controls

Figure 3 displays the front panel layout of the Electro-Voice MA-1212 Professional Mixer/Amplifier. Key controls and indicators visible include:

1. "Mute" function switch: Activates or deactivates the "Voice Priority" or "ducking" function for Input 1.
2. Auxiliary 1&2 Controls: Adjust the level of the two stereo summing auxiliary inputs.
3. Input 1-10 Controls: Adjust the levels of the 10 multi-use inputs.
4. Music signal monitor output level control: A screwdriver-adjustable control for setting the volume of a headphone connected to the "MONITOR OUTPUT" (4) or a small speaker connected to the 1W 8 ohm terminals on the rear panel (25). Clockwise rotation increases volume.
5. Overload Indicator Light: Illuminates and interrupts the output signal when the amplifier's output is overloaded. The output resumes when the volume is lowered or the offending load is removed.
6. Power Switch and Power Indicator: This switch supplies power to the unit; the indicator lights when power is applied.
7. Master Control: Adjusts the level of the combined input signals to the power amplifier.
8. Treble Control: Adjusts high-frequency response, offering up to 7 dB boost or 12 dB cut at 10 kHz.
9. Bass Control: Adjusts low-frequency response, offering up to 7 dB boost or 12 dB cut at 100 Hz.

Rear Panel Controls and Connections

Figure 4 presents the rear panel layout of the Electro-Voice MA-1206/MA-1212 mixer/amplifiers. Prominent features include:

1. Main cord connector: For connecting the supplied AC line cord.
2. AC fuse: The fuse can only be changed by an EV service center in case of a fault or supply voltage change.
3. "GND" screw: Provides a ground connection for the amplifier's metal parts if the main outlet lacks a ground conductor.
4. Terminals for DC battery supply: Two terminals for connecting an external 24V DC power supply (e.g., a battery). The amplifier automatically switches to this source during a power outage.
5. Output terminals: For all speaker connections, supporting 25V, 70V/100V, and low impedance speaker configurations. Refer to the "Output Connections" section for details.
6. "PRE OUT" terminal: Outputs a mixed audio signal of all connected sources, usable for external power amplifiers, signal processors, or other appliances. The unbalanced signal is affected by individual input controls. Remove the bridging-strip between this and the "MAIN IN" terminal (16) before use.
7. "MAIN IN" terminal: After removing the bridging-strip between "PRE OUT" and "MAIN IN", an external signal processor can be inserted in the audio chain between the preamplifier and power amplifier stages.
8. "AUX 1" and "AUX 2" inputs: Two RCA connectors for high-level unbalanced signal sources like tuners, cassette decks, or CD players. An input level switch (20) helps balance input sensitivity.
9. INPUT 1-10 jacks: Ten combination balanced/unbalanced jacks (XLR and 6.3mm) for condenser microphones (requiring 24V phantom power), dynamic microphones (30-600 ohms), or high-level sound sources. Note: Connecting unbalanced microphones with phantom power on can cause severe damage; always turn phantom power off before plugging/unplugging cables.
10. INPUT 1-10 sensitivity switches: Select "LINE" for high-level sources, "MIC" for dynamic microphones, or "24V" for phantom power to condenser microphones. Operate the "24V" switch only when the master volume is at minimum.
11. AUX1-2 input sensitivity switch: Select "1" for CD players, "2" for AM/FM tuners, "3" for balanced cassette players, or "4" for general high-level outputs.
12. TEL. Paging input level control: Adjusts the volume for the "Tel. Paging" (23) terminals. Recommended to set to "0" when not in use.
13. LINE OUTPUT CONNECTOR: An XLR balanced output that mixes audio signals from all sources. It can feed external tape decks or other appliances. The output level can be fixed or variable, controlled by the master volume knob.
14. Input "TEL.Paging": Connects to an auxiliary signal (600 ohms) and features the "Voice Priority" function, which overrides other inputs when an auxiliary message is sent.
15. "Priority" terminal: Short-circuiting these terminals (e.g., with a switch) attenuates audio signals from "AUX1", "AUX2", "CASSETTE", and "TUNER", while leaving inputs 1-10 unchanged.
16. Output terminal for auxiliary loudspeaker: For connecting a small external 8 ohm loudspeaker driven by an internal 1-watt auxiliary amplifier. The output signal includes mixed audio from "AUX1", "AUX2", "CASSETTE", and "TUNER", controlled by their respective volume controls and the music signal level control (4).
17. DC switch: Turns the battery supply on or off.

Appendices

Appendix A: Limited Warranty

Electro-Voice amplifiers are guaranteed against malfunction due to defects in materials or workmanship for three (3) years from the date of original purchase. Repairs or replacements will be made without charge, and the product will be returned prepaid. The warranty does not cover exterior finish, specific items listed in product sheets, malfunctions from improper use or operation, or repairs by unauthorized personnel.

To obtain warranty service, deliver the product, prepaid, to Electro-Voice Service or an authorized representative with proof of purchase. Authorized service representatives can be found by contacting Electro-Voice Service at 12000 Portland Avenue South, Burnsville, MN 55337, Phone: (877) 863-4166.

Incidental and consequential damages are excluded. This warranty grants specific legal rights that may vary by state.

Appendix B: Safety Guidelines

Operate the amplifier under appropriate conditions, ensuring sufficient ventilation and avoiding direct sunlight or heat sources. Install loudspeaker systems in locations free from extreme vibration or mechanical oscillation.

Electrical Safety: Do not risk electro-shock. Ensure all connections are made before connecting to the main supply. Verify all external connections are complete and free from short-circuits. Installations must comply with local laws, regulations, and standards.

AC Power Supply: This equipment operates from a power source not exceeding 244 VAC.

DC Power Supply: A 24V DC power source (e.g., a battery) connects to terminals (13). Use cables of at least 2.5mm diameter to minimize voltage drop and prevent thermal overload. Amplifier power is switched on/off via the power switch (6).

Safety Precautions:

1. Read all safety information carefully.
2. The power supply voltage poses a risk of electrical shock; never install, connect, or disconnect equipment with the power supply switched on.
3. Metal parts are earthed via the power cable. If the power socket lacks an earth connection, consult a qualified electrician.
4. Ensure the power supply cable cannot be trodden on or crushed.
5. There are no user-serviceable parts inside.
6. Prevent objects or liquids from entering the amplifier to avoid short circuits.
7. Never attempt unauthorized repairs. Contact authorized service centers for malfunctions, damaged cables, liquid ingress, or heavy impact.
8. For long periods of non-use, switch off and disconnect the power supply cable.
9. If the equipment emits strange odors or smoke, switch it off immediately and disconnect power.

Technical Specifications

Contact Information

U.S.A. and Canada:

• For customer orders, contact the Customer Service department at: 800/392-3497, Fax: 800/955-6831
• For warranty repair or service information, contact the Service Repair Department at: 800/685-2606
• For technical assistance, contact Technical Support at: 866/78-AUDIO

All Other International Locations:

• Phone: 952-884-4051, Fax: 952-736-4212

Specifications subject to change without notice.

Printed in U.S.A.

© Telex Communications, Inc. 10/2002

Part Number 38110-190 Rev A

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