How to choose a headphone amplifier
Picking a headphone amplifier is a matching exercise — not a “bigger is better” one. The headphone's impedance and sensitivity set how much voltage and current you need, and the amp's output impedance sets how clean the bass response will be.
Step 1 — measure the load
Read your headphone's impedance in ohms and its sensitivity in dB/mW (or dB/V). Low impedance + low sensitivity (e.g. planar magnetics at 32–50Ω and 86–90dB) demands current; high impedance + high sensitivity (e.g. 300Ω dynamics at 102dB) demands voltage.
Step 2 — calculate required power
Target a peak listening level of 100–110dB SPL. Convert your sensitivity (dB/mW) to the milliwatts needed: each 3dB up doubles required power. Reserve at least 10dB of headroom over your average listening level to avoid clipping on transients.
Step 3 — check the damping factor
Damping factor = headphone impedance ÷ amp output impedance. Below 8:1 you start to hear bass bloom on low-impedance, low-damping headphones. For 32Ω planars, that means an amp with sub-4Ω output impedance.
Step 4 — pick the topology
Class A: lowest distortion, runs hot, current-limited. Class AB: best price/performance ratio. Class D: efficient, sometimes audibly aggressive on cymbals. Tubes: higher output impedance — better for 300Ω+ dynamics than for planars.
Step 5 — consider single-ended vs balanced output
Balanced outputs (4.4mm Pentaconn or 4-pin XLR) give you the full bridge-tied-load power without ground-shared crosstalk. For headphones that ship with a detachable cable and a balanced upgrade option, the practical SNR gain is real.