R7

Headroom Notes

Mains-powered Android player with a real headphone amplifier, and — unlike every laptop and motherboard in this category — it publishes the numbers the calculator needs. The 6.35 mm output in ultra-high gain is specified at 1250 mW into 32 ohms and 160 mW into 300 ohms; the second figure is the one that pins the voltage, because at 300 ohms the amplifier is voltage-limited rather than current-limited. sqrt(0.160 W x 300 ohm) = 6.9 V, against 6.3 V derived from the 32 ohm figure. Output impedance is under 0.5 ohm, so it will not reshape a multi-driver IEM's response.

Production Warning

The 2.5 W bus-power figure is not FiiO's: it is the USB 2.0 specification floor for the USB-A host port FiiO documents as "USB A (USB2.0) x 1 (data transfer)". The Type-C port is the opposite direction — it makes the R7 a USB DAC for a computer, not a power source. The 4 uV noise figure is for the phone outputs; the line output is quieter at 2.7 uV.