Moondrop Dawn Pro with Sennheiser HD 600: two volts is 7 dB short
The named dongle pairing, and on the 3.5 mm socket the answer is no: 103.0 dB against a 110 dB target. The same dongle with an HD 650 reaches 109.0 — two Sennheisers of identical impedance, six decibels apart. And the fix on this page is a cable, not an amplifier.
Not enough on the 3.5 mm socket — 7.0 dB short — and the fix is a cable, not an amplifier.
Level. The HD 600 is 300 Ω and 97 dB/V, six decibels quieter per volt than the HD 650 it is constantly confused with. The Dawn Pro publishes 2 V on the 3.5 mm output, so the peak level is 103.0 dB against a 110 dB target — headroom −7.0 dB. The same dongle in the same socket with an HD 650 reaches 109.0 dB. Two Sennheisers of identical impedance, six decibels apart, one crossing the line and one not: impedance was never the variable.
What the chain would have to give. 4.47 V, 14.9 mA, 66.5 mW. The current is trivial — 300 Ω is an easy load. What runs out is voltage.
What we cannot say. Moondrop publishes no output impedance for the Dawn Pro, so our damping ratio reads «unknown» rather than a number. It is not zero; we simply do not know it. And the 2 V itself comes from a row headed «Line Output: 4.4mm: 4Vrms / 3.5mm: 2Vrms» — the Dawn Pro has no line outputs, those are the headphone jacks, quoted with no load named. An unloaded voltage is a ceiling, not a drive rating, so 103.0 dB is already an upper bound.
The pearl: the other socket on the same dongle is 4 V, and that is exactly +6.0 dB. 103.0 dB becomes 109.0 dB, and the HD 600 lands where the HD 650 already was. The cheapest thing that fixes this page is a balanced cable — a passive object with no electronics in it. Our calculation cannot show that: the schema carries one voltage per source and has no balanced-output field, so the site would answer «buy an amplifier» to a question a cable settles.