OpenAudio L2H-1202 / L2H-1204 Audio Matching Transformer

L2H-1202

L2H-1204

1. Product Overview

OpenAudio L2H-1202/1204 is a dual-channel audio line matching transformer module designed to convert low-impedance (4Ω/8Ω) amplifier outputs into standard 70V/100V constant-voltage outputs, with up to 120W output capacity per channel.

The device is widely used in commercial broadcasting and background music systems, effectively solving challenges such as long-distance transmission and multiple speaker parallel connections.

This device adopts a standard 1U rack-mounted structure with an industrial-grade shielded chassis, featuring low audio loss and high operational stability. It is widely used in shopping malls, hotels, office buildings, campuses, and industrial parks for public broadcasting systems. It is a core supporting device for implementing true constant-voltage audio distribution.

Product Positioning

• Product Model: OpenAudio L2H-1202/1204
• Device Type: Dual-channel audio impedance/voltage matching transformer
• Output Capacity: Up to 120W per channel (70V/100V constant-voltage output)
• Output Mode: Selectable 70V / 100V constant voltage
• Core Application: Low-impedance to constant-voltage conversion, long-distance audio transmission, distributed multi-speaker reinforcement

2. Key Features

• Dual-channel independent operation: Each channel is fully isolated with a Max output capacity of 120W, supporting stereo or dual-zone applications without interference.
• Dual voltage mode switching: Supports standard 70V and 100V constant-voltage outputs for flexible deployment based on distance and speaker configuration.
• High-fidelity, low-loss design: Audio-grade transformer core with insertion loss ＜1dB and flat frequency response, ensuring accurate sound reproduction without noticeable distortion or low-frequency attenuation.
• Standard rack installation: 1U rack-mount design compatible with all 19-inch racks, enabling clean installation and efficient space usage.
• Industrial-grade reliability: Full metal shielding minimizes electromagnetic interference and ensures stable 24/7 operation.
• Easy wiring and maintenance: Removable Phoenix connectors with clearly defined input/output sections for quick installation and servicing.

3. Technical Specifications

3.1 Electrical Specifications

3.2 Mechanical and Environmental Specifications

4. Panel and Interface Description

4.1 Front Panel

4.2 Rear Panel Interfaces

All connections are located on the rear panel, divided into input, output, voltage selection, and grounding sections. Each channel is independent.

1. CH1 Input: Connect to amplifier CH1 low-impedance output
2. CH2 Input: Connect to amplifier CH2 low-impedance output
3. CH3 Input (L2H-1204 only): Connect to amplifier CH3 low-impedance output
4. CH4 Input (L2H-1204 only): Connect to amplifier CH4 low-impedance output
5. CH1 Output: 70V/100V output to speaker line
6. CH2 Output: 70V/100V output to speaker line
7. CH3 Output (L2H-1204 only): 70V/100V output to speaker line
8. CH4 Output (L2H-1204 only): 70V/100V output to speaker line
9. Voltage Selection: Independent 70V / 100V / COM terminals per channel
10. Ground Terminal: System grounding for noise reduction and safety

5. System Installation and Wiring Guidelines

5.1 System Topology

Audio Source → Power Amplifier → OpenAudio L2H-1202/1204 → Constant-voltage speaker system

5.2 Installation

• Install in standard 19-inch rack
• Place near amplifier to reduce cable length
• Ensure proper ventilation

5.3 Wiring

• Use 1.5–2.5mm² cable for amplifier input
• Select voltage mode using terminal jumpers
• Connect speakers in parallel
• Ensure proper grounding

5.4 Load Requirements

• 70V mode: ≥40Ω per channel
• 100V mode: ≥80Ω per channel
• Do not operate without load

6. Application Scenarios

6.1 Voltage Mode Selection

• 70V: short distance (<500m), dense speaker deployment
• 100V: long distance (500–1000m), wide-area coverage

6.2 Wiring Recommendations

• Input side: shielded cable
• Output side: 1.5–4mm² depending on distance

7. Maintenance and Troubleshooting

Routine Maintenance

• Inspect connections regularly
• Clean dust
• Maintain proper environment

Common Issues

8. Safety Instructions

• Power off before wiring
• Do not operate without load
• Avoid overload
• Do not disassemble

9. Standard Accessories

• Main unit ×1
• Rack screws ×4
• Documentation

10. Engineering Notes (Critical Operation Guidelines)

The input power must not exceed the transformer’s rated power (120W per channel). For reliable long-term operation, it is recommended to operate within 70–85% of the rated capacity.

11. 70V/100V Constant Voltage: Transformer-Based vs. DSP-Limited Systems

• Behavior at System Limits

• True Constant Voltage vs. DSP-Limited Output

• How Transformerless 70V/100V Systems Actually Work