RME ADI-2 Pro FS R: power output and what it will drive

The RME ADI-2 Pro FS R is an audio interface at $2199. It delivers 3.0 W into 32Ω and 317 mW into 300Ω, which ranks it 27 of 280 for raw power among the sources in this database.

Measured at 100 dB SPL it has comfortable headroom on 565 of the 567 dynamic and planar headphones catalogued here and enough but not generous on 2. The maker publishes a maximum output voltage but no power figure at any load, so every number here is an upper bound rather than a rating. Output noise is not published, so the hiss estimate cannot be run.

The manufacturer publishes a maximum output of 9.75 V but no power rating at any load. Every figure above is therefore a ceiling: the real output into a low impedance will be lower, possibly much lower.

The balanced output is rated separately: 11.8 W into 32Ω through the balanced jack.

Derivation holds output voltage steady between and beyond the published loads rather than output power, because that is what an amplifier actually does. The full method is written up here.

The noise figure above is converted, not read. RME does not print microvolts for this one. It prints a signal-to-noise ratio together with the voltage that ratio is referenced to, in the same block of the same table: “Signal to Noise ratio (SNR) @ +7 dBu: 118 dB RMS unweighted, 121 dBA | Output level at 0 dBFS, Lo-Power, load 8 Ohm or up: +7 dBu (1.73 V)”. From those two numbers the noise follows by one division — 1.73 V ÷ 10^(118/20) — which is where the 2.18 µV comes from, at the Lo-Power setting, podaje OBA: unweighted i A-weighted. This is the same situation as a sensitivity printed per volt instead of per milliwatt: published, but in a convention nobody converts.

Source: rme-audio.de.

Ordered from easiest to hardest to drive. Headroom is measured at 100 dB SPL, which is louder than almost anyone listens — a small negative number means the source still plays loud, just without reserve for peaks.

These figures come from each manufacturer's own sensitivity rating. A handful of planars — the HiFiMAN Susvara and the Abyss AB-1266 in particular — are widely reported to need far more than their published sensitivity implies, so treat a bare pass on those as optimistic rather than settled.

At 2.18 µV of output noise, here is where that noise lands in the five most revealing in-ears in the database.

This one hisses. With the most sensitive in-ears in the database its own noise lands around 28 dB SPL, which you will hear between tracks and in quiet passages.

At 0.1Ω output impedance this source satisfies the one-eighth rule with every headphone in the database, down to the 3Ω in-ears. Nothing here will have its frequency response shaped by the source.

The rule is a rule of thumb, not physics: a source impedance below one eighth of the headphone's keeps the interaction under about 1 dB. The checker works it out for any pair.

Of the 280 sources here, 10 do everything the RME ADI-2 Pro FS R does as a headphone output: reach 100 dB on every headphone it reaches, stay inside the one-eighth rule wherever it does and stay under the audible-hiss threshold wherever it does. The cheapest of them is the Schiit Magni Unity at $119, against this one’s $2199 — $2080 less, and a desktop amplifier rather than an audio interface.

This counts a headphone output and nothing else. Inputs, converters, microphone preamps, balanced outputs, the volume control, the case and the warranty are all outside it, and any of them can be the reason to buy the dearer box. What the count does say is that the three numbers a maker can be held to do not separate them.

Worked out in advance against its closest rivals: vs Audient Horizon 8P · vs Audient ORIA · vs Merging Anubis · vs RME Babyface Pro FS · vs RME Fireface UCX II · vs RME Fireface UFX II · vs RME Fireface UFX III. Each of those pages lists the headphones that tell the two apart.

Or put any two side by side in the source comparison tool, or run your own headphones through the amplifier matcher. Or see every RME source in the database, and how much of what this site says about them came from RME’s own documents.