Moondrop Starfield II: how much amplifier do you need?

The Moondrop Starfield II is 15Ω with a sensitivity of 103.8 dB/mW, which is 122.0 dB/V. To reach 100 dB SPL — genuinely loud, louder than most people listen — it needs 0.42 mW, or 79 mV across the drivers.

That puts it in the easy category. A phone, a laptop headphone jack or the cheapest USB dongle will drive it to painful levels. Of the 280 sources in the database, 280 have at least 10 dB of headroom and another 0 have enough. The cheapest portable source that does the job is the Apple USB-C dongle (US) at $9.

The two numbers that decide everything

Impedance15 Ω
Sensitivity103.8 dB/mW
Sensitivity (voltage)122.0 dB/V
Power for 100 dB SPL0.42 mW
Voltage for 100 dB SPL79 mV
TypeIn-ear monitor
Easy to drive — anything will do it
All 280 sources at 100 dB SPL into 15Ω
Comfortable 280Enough 0Marginal 0Not enough 0
Cheapest portable source that does it
$9 · USB dongle · +15 dB headroom
Cheapest desktop amp with 10 dB to spare
$75 · desktop DAC/amp · +22 dB headroom

Sensitivity here is in dB per milliwatt. Why the unit matters.

Where this sensitivity figure comes from

Moondrop publishes this as 122 dB/Vrms ((@1kHz)) — a figure per volt, not per milliwatt. At 15Ω the two differ by 18.2 dB, so the 103.8 dB/mW above is that published number converted, not a different measurement.

This is the conversion that online calculators skip. Quote the per-volt number as if it were per-milliwatt and this headphone looks 18 dB easier to drive than it is — which is roughly the difference between a dongle being enough and not being enough.

Moondrop prints the impedance as 15Ω±15% (@1kHz), not as a bare number. Everything on this page is calculated with the nominal 15Ω, and the rest of that line is quoted here rather than tidied away, because how a figure is qualified is part of the specification too.

Source: moondroplab.com. How this data was built.

What is printed there, and what it is worth

As it is labelledAs printedToleranceStandard
Frequency Response12Hz-24kHz (IEC61094, Free Field)not printedIEC61094 (free field)
Effective Frequency Response20Hz-20kHz (IEC60318-4, -3dB)-3 dBIEC60318-4

Moondrop prints two frequency ranges for the Moondrop Starfield II. The wide one carries no conditions at all; the narrow one names a measurement standard and a tolerance. Only the second is a specification — the first is a headline.

This is one of only 58 models — out of the 490 whose maker prints a range at all — that also print the tolerance. That is what makes it a specification rather than a headline.

Only what the maker printed; maker by maker.

Power, voltage and current by listening level

LevelWhat it isPowerVoltageCurrent
85 dB SPLquiet background listening0.01 mW14 mV0.9 mA
95 dB SPLnormal listening0.13 mW44 mV3.0 mA
100 dB SPLloud listening0.42 mW79 mV5.3 mA
105 dB SPLvery loud1.3 mW0.14 V9.4 mA
110 dB SPLpeaks on dynamic music4.2 mW0.25 V16.7 mA

Most people listen between 75 and 85 dB; the 100 dB row leaves room for peaks.

The cheapest sources that drive them with room to spare

The 15 cheapest of the 280 sources here that reach 100 dB SPL into 15Ω with at least 10 dB of headroom and no known hiss or output-impedance problem with these headphones. All 280 sources, judged for these headphones.

SourceTypePricePower into 15ΩHeadroomVerdict
FiiO SnowSky Tiny AUSB dongle$2242 mW+20 dBComfortable
FiiO SnowSky Tiny BUSB dongle$2264 mW+22 dBComfortable
Tanchjim Stargate IIUSB dongle$4077 mW+23 dBComfortable
ddHiFi TC35ALUSB dongle$4698 mW+24 dBComfortable
ddHiFi TC35AirUSB dongle$4698 mW+24 dBComfortable
Fosi Audio N3Bluetooth receiver$5065 mW+22 dBComfortable
Hidizs SD2USB dongle$5033 mW+19 dBComfortable
iFi GO linkUSB dongle$5933 mW+19 dBComfortable
Kiwi Ears Allegro ProUSB dongle$6032 mW+19 dBComfortable
ddHiFi TC35Pro (Mountain2)USB dongle$6630 mW+19 dBComfortable
DUNU DTC 480USB dongle$7030 mW+19 dBComfortable
EPZ TP35 ProUSB dongle$7053 mW+21 dBComfortable
Aiyima A2 Prodesktop DAC/amp$7570 mW+22 dBComfortable
ddHiFi TC35Pro (Eye2)USB dongle$7630 mW+19 dBComfortable
ddHiFi TC44 Pro E2USB dongle$99117 mW+24 dBComfortable

The three ways a source goes wrong

Hiss. At 122.0 dB/V these are sensitive enough to reveal a source's own noise floor. The noisiest source in the database, the Schiit Mjolnir 3, would put its hiss at roughly 30 dB SPL in these headphones — clearly audible in quiet passages. Check your own source.

Output impedance. At 15Ω these want a source output impedance below 1.88Ω to satisfy the one-eighth rule; 39 of the 192 sources that publish one miss it. Check yours here.

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