FiiO BTR17: power output and what it will drive

The FiiO BTR17 is a Bluetooth receiver at $199. It delivers 280 mW into 32Ω and 30 mW into 300Ω, which ranks it 138 of 280 for raw power among the sources in this database.

Measured at 100 dB SPL it has comfortable headroom on 549 of the 567 dynamic and planar headphones catalogued here, enough but not generous on 16, only marginal on 1 and not enough power for 1. Desktop mode over USB. The most powerful of the BTR line.

The manufacturer publishes 330 mW into 16Ω, 280 mW into 32Ω, 30 mW into 300Ω. Everything else in the table above is worked out from those figures, and this table says which is which.

The balanced output is rated separately: 650 mW into 32Ω through the 4.4mm 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.

Source: fiio.com.

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 3.0 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 31 dB SPL, which you will hear between tracks and in quiet passages.

At 1Ω output impedance, the one-eighth rule says this source suits headphones of 8.0Ω and above. 15 of the 567 models here fall below that. Most of them are multi-driver in-ears, and 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.

Of the 280 sources here, 8 do everything the FiiO BTR17 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 FiiO KA11 at $29, against this one’s $199 — $170 less, and a USB dongle rather than a Bluetooth receiver.

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 FiiO BTR11 · vs FiiO BTR13 · vs FiiO BTR15 · vs FiiO BTR5 2021 · vs FiiO BTR7 · vs iFi GO blu · vs Shanling UP5. 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 FiiO source in the database, and how much of what this site says about them came from FiiO’s own documents.