RME Babyface Pro FS: power output and what it will drive

The RME Babyface Pro FS is a audio interface at $899. It delivers 374 mW into 32Ω and 40 mW into 300Ω, which ranks it 76 of 156 for raw power among the sources in this database.

Measured at 100 dB SPL it has comfortable headroom on 389 of the 396 dynamic and planar headphones catalogued here, enough but not generous on 6 and only marginal on 1.

The manufacturer publishes a maximum output of 3.46 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.

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.

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 HE-6se 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 6.3 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 30 dB SPL, which you will hear between tracks and in quiet passages.

At 10 Ω output impedance, the one-eighth rule says this source suits headphones of 80.0Ω and above. 342 of the 396 models here fall below that, mostly multi-driver in-ears, where the mismatch tilts the frequency response audibly rather than subtly.

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.

Or put any two side by side in the source comparison tool, or run your own headphones through the amplifier matcher.