Power output vs. impedance: Most amplifier specs list power at standard impedances (32Ω, 300Ω, 600Ω) which may not match your headphones' impedance. Use these calculations to ask retailers about the voltage and current capabilities needed for your specific headphones.
Headroom for musical peaks: Music has a crest factor of 10-20dB, meaning peaks can be 10-20dB louder than the average level. If you listen at a comfortable 80dB average, musical peaks hit 90-100dB. An amplifier capable of 110-115dB ensures these transient peaks reproduce cleanly without clipping or distortion, providing the headroom needed for dynamic music at safe listening levels.
Never actually listen above 115dB! These calculations show capability for adequate headroom. Comfortable listening happens around 70-85dB for extended sessions.
Match your headphone's impedance needs: High-impedance headphones (>100Ω) need voltage capability, while low-impedance headphones (<32Ω) need current capability.
Output impedance matching: Choose an amplifier whose output impedance is no more than 1/8 of your headphones' impedance (some prefer 1/10). For example, 32Ω headphones should use amps with ≤4Ω output impedance, while 300Ω headphones can work with ≤37Ω output impedance. Higher ratios can cause frequency response shifts and poor damping.
Reading amplifier specifications: Many amplifier spec sheets list power output at specific impedances (e.g., "100mW at 32 ohms") rather than voltage capabilities. To convert power (in watts) and impedance (in ohms) to voltage, use: Voltage = √(Power × Impedance). For example, 100mW at 32 ohms = √(0.1 watts × 32 ohms) = 1.79 volts. Compare this calculated voltage to your headphones' voltage requirement.
Consider your setup: Desktop amplifiers generally handle high-impedance headphones better than portable devices, though modern portable amps are increasingly capable.
Planar magnetic headphones: Many planars have lower sensitivity and impedance than dynamic headphones. Focus on finding an amplifier that can deliver the calculated current requirements cleanly with low output impedance rather than seeking 'extra' power beyond what the math shows.
Remember: More power isn't always better - there are diminishing returns, and proper impedance matching matters more than raw specifications. Every setup is unique, so personal consultation can save you time and money.
