The first choice for professional audio? The practical advantages of Class H amplifiers in large-scale performances

1. Practical Advantages of Class H Amplifiers

• High Efficiency: Reduced Energy Consumption, Extended Equipment Life

Problem: Large-scale performances often require long periods of high power output. Traditional Class AB amplifiers have an efficiency of only 30%-50%, converting a large amount of electrical energy into heat, resulting in high heat dissipation pressure and high energy costs.

Advantages of Class H Amplifiers:

Dynamic Voltage Switching: Adjusts the supply voltage in real time based on the input signal, achieving efficiencies of 60%-75%, significantly reducing heat buildup.

Reduced Cooling Requirements: Reduces fan noise, making it suitable for theaters and recording studios where quiet operation is paramount.

• High Fidelity: Balancing Efficiency and Sound Quality

Problem: Class D amplifiers offer high efficiency but a more "digital" sound, while Class AB offers good sound quality but lower efficiency. How should professional audio professionals choose between these two options?

Advantages of Class H Amplifiers:

Linearity close to Class AB: Uses a low-voltage supply in the low- and medium-power range, reducing crossover distortion.

High Dynamic Response: Instantaneous high-voltage operation allows for handling sudden musical peaks (such as drum beats and symphonic climaxes). Measured Data: At 1kHz @ 8Ω load, Class H THD (Total Harmonic Distortion) is ≤0.03%, comparable to Class AB and far superior to standard Class D.

• Stability: Adaptable to Harsh Performance Environments

Issue: Outdoor performances may face voltage fluctuations, high temperature, and high humidity, requiring amplifiers with extremely high reliability.

Advantages of Class H Amplifiers:

Wide Voltage Compatibility: Supports AC 100V to 240V input, making it suitable for standardized equipment on global tours.

Complete Protection Circuitry: Overload, short-circuit, and overheating protection mechanisms are more sensitive than traditional Class AB amplifiers.

Industry Feedback: A touring sound engineer noted, "Class H amplifiers operated continuously for 8 hours outdoors at 40°C in summer without thermal shutdown."

• Recommended Application Scenarios

Main PA System: Main stage at a large music festival, requiring long-term high power output.

Stage Monitor: Low heat generation prevents localized overheating on the stage from affecting musicians.

Fixed Installation Locations: Theaters, auditoriums, and other locations requiring high acoustics and energy efficiency.

2. Common Problems and Solutions of Class H Speaker Amplifiers

The amplifier is overheating, even triggering overheat protection.

Possible Causes:

Prolonged high-power output: Although Class H amplifiers are more efficient than Class AB amplifiers, they still generate heat when operating at full load.

Poor heat dissipation: Blocked vents, fan failure, or excessively high ambient temperature.

Unstable power supply voltage: Excessive voltage places an increased strain on the internal regulation circuitry.

Solution:

Reduce the load: Avoid driving low-impedance speakers (e.g., below 4Ω) at full power for extended periods.

Improve heat dissipation:

Ensure adequate space around the device (recommended ≥20cm).

Regularly clean dust from the cooling fan and vents.

Check the power supply: Use a stabilized power supply or UPS to avoid voltage fluctuations.

Poor sound quality (distortion, increased noise floor)

Possible Causes:

Power supply interference: Low-quality switching power supplies or poor grounding introduce noise.

Input signal overload: The output level of the preamplifier (e.g., mixing console) is too high, causing clipping and distortion.

Speaker impedance mismatch: The speaker impedance is too low (e.g., 2Ω), exceeding the amplifier's capability. Solution

Optimize the signal chain:

Use balanced (XLR/TRS) connections to reduce interference.

Ensure the input signal level is within the amplifier's recommended range (typically -10dBV to +4dBu).

Impedance matching:

Check the speaker impedance (typically 4Ω/8Ω) and avoid ultra-low impedance loads.

If driving a 2Ω load, choose a professional model that supports multi-channel parallel connection.

No output at power-on or protection mode frequently triggers

Possible causes:

Short-circuit protection: The speaker cable is short-circuited or the amplifier output terminals are poorly connected.

Overload protection: The input signal's transient peak is too high (such as when plugging or unplugging cables).

DC offset protection: A fault in the amplifier's internal circuitry causes a DC output.

Solution

Check the wiring:

Use a multimeter to measure the speaker cable for shorts (the impedance should be the nominal value for the speaker).

Ensure the banana plugs/binding posts are secure and free of oxidation.

Soft-start system:

Lower the volume before powering on to avoid sudden level surges.

Use a power sequencer with a soft-start function. Send for repair inspection: If the problem persists, there may be a problem with the internal power tube or protection circuit, requiring professional repair.

Dynamic Compression (the sound becomes "soft" at high volumes)

Possible Causes

Insufficient power supply: Class H amplifiers rely on dynamic voltage switching and cannot maintain peak output when power reserves are insufficient.

Cooling Limitations: High temperatures cause the amplifier to automatically reduce gain (thermal compression).

Solutions

Upgrade the power supply:

Select a power supply with greater power headroom (recommended to be at least 1.5 times the amplifier's rated power).

Use a linear power supply (LPS) instead of a switching power supply (SMPS) to reduce ripple interference.

Optimize cooling: Install an auxiliary cooling fan or lower the ambient temperature.

Insufficient low-frequency control (loose, lacking punch)

Possible Causes

Low damping factor: Class H amplifiers typically have a lower damping factor than Class AB amplifiers, resulting in slightly less control over the woofer.

Speaker matching issues: Low sensitivity (<90dB) or large subwoofers require higher current drive.

Solutions

Select a model with a high damping factor: Professional-grade Class H amplifiers can have a damping factor of over 200. Increasing the amplifier's power reserve: When driving a subwoofer, the recommended power rating is 1.5 times or greater than the speaker's rated power.

Pairing with a dedicated Class D low-frequency amplifier: For ultra-low frequencies (20-80Hz), a Class D amplifier can be used to enhance control.

Key points for maintaining Class H amplifiers

3. Class H Speaker Amplifier FAQ (Frequently Asked Questions)

Basic Concepts

Q1: What is a Class H Amplifier?

A Class H amplifier is an audio power amplifier that improves efficiency by dynamically adjusting the supply voltage. It combines the sound quality of a Class AB amplifier with the efficiency of a Class D amplifier, making it particularly suitable for professional audio applications requiring high power output.

Q2: What is the difference between Class H and Class AB and Class D amplifiers?

Class AB: Good sound quality but low efficiency (approximately 50%) and high heat generation.

Class D: High efficiency (>90%) but slightly "digital" sound quality.

Class H: Efficiency falls between the two (60-75%), with sound quality close to Class AB.

Performance Characteristics

Q3: Why is a Class H amplifier more efficient than a Class AB amplifier?

Class H uses a multi-level supply voltage, dynamically switching the supply voltage based on the input signal size to reduce energy waste. Low voltage is used for small signals and high voltage is used for large signals.

Q4: What is the sound quality of a Class H amplifier?

The sound quality is similar to that of a Class AB amplifier, with total harmonic distortion (THD) typically less than 0.05%, and excellent mid- and high-frequency performance. However, the control in the very low frequency band (below 20Hz) is slightly inferior to that of Class AB.

Usage Issues

Q5: What should I do if my Class H amplifier overheats excessively?

Ensure adequate ventilation (leave 20cm of space around the amplifier).

Avoid driving low-impedance speakers (e.g., below 4Ω) at full power for extended periods.

Clean the cooling fan and vents regularly.

Consider installing an auxiliary cooling device.

Q6: Why does my Class H amplifier frequently enter protection mode?

Possible causes:

Short-circuited or poor contact in the speaker cables.

Input signal overload.

Overheating due to poor heat dissipation.

Unstable power supply voltage.

Solutions:

Check all cables.

Reduce the input level.

Improve heat dissipation.

Use a regulated power supply.