Headphones that measure well can sound wrong on the wrong amplifier. The cause is usually an
impedance mismatch, and unlike most audio disagreements it is arithmetic rather than opinion.

The eighth rule

Aim for a source output impedance no higher than one-eighth of the headphone’s nominal
impedance. A 32-ohm headphone wants a source under about 4 ohms; a 300-ohm headphone tolerates
up to roughly 37 ohms.

Break the rule and the headphone’s impedance curve starts shaping the frequency response.
Dynamic drivers have an impedance peak at their resonant frequency, usually in the bass. Feed
them from a high-impedance source and that peak becomes a bass bump — audible, unintended, and
different on every model.

Sensitivity decides how much power you need

Sensitivity is quoted in dB per milliwatt or dB per volt. A headphone rated 100 dB/mW reaches
comfortable listening levels on almost anything. One rated 90 dB/mW needs ten times the power for
the same output. Combine low sensitivity with high impedance and a laptop jack simply cannot
deliver enough voltage swing — the result is thin, dynamically flat sound that people mistake for
the headphone’s character.

Do you need a separate DAC?

Modern integrated DACs are good. The audible failures in a signal chain are almost never
converter resolution — they are noise from a shared power rail, a hissy amplifier stage, or an
impedance mismatch. A combined DAC/amp unit with a clean, low-impedance output solves more real
problems than separates chosen on converter spec.

Separates start earning their keep when you need specific I/O, balanced outputs, or the ability
to upgrade one half of the chain independently.

Practical pairings

• High-impedance open-back (250-600 ohm): needs voltage. Look for a desktop
  amp quoting output into 300 ohms, not just into 32.
• Low-impedance planar (below 50 ohm, low sensitivity): needs current. Check
  the milliwatt figure at the actual impedance.
• Sensitive IEMs: need a low noise floor above all. Many powerful desktop
  amps hiss audibly into IEMs; a dedicated low-gain setting matters more than raw output.

Frequently asked questions

Will a headphone amp make quiet headphones louder only?

Loudness is the visible part. Adequate power also preserves transient dynamics and keeps the
low end controlled at volume.

Does a more expensive DAC chip sound better?

Implementation dominates. Power supply design and analogue output stage matter far more than
the chip part number.

Is balanced output better for headphones?

It typically doubles available voltage swing and can lower crosstalk. Useful for demanding
headphones, largely irrelevant for efficient ones.