FD15 vs FP3: which needs more amplifier?

The FiiO FD15 is 32Ω at 112.0 dB/mW; the FiiO FP3 is 36Ω at 105.0 dB/mW. This page covers what they ask of an amplifier, not how they sound.

The FP3 needs 7.0 dB more than the FD15 to reach the same loudness — 0.32 mW against 0.06 mW.

Side by side

The numbers that decide it

Specification	FD15	FP3
Impedance	32 Ω	36 Ω
Sensitivity	112.0 dB/mW	105.0 dB/mW
Sensitivity (voltage)	126.9 dB/V	119.4 dB/V
Power for 100 dB	0.06 mW	0.32 mW
Voltage for 100 dB	45 mV	0.11 V
Current for 100 dB	1.4 mA	3.0 mA
Highest source impedance that leaves them alone (one-eighth rule)	4.00 Ω	4.50 Ω
Sources that reach 100 dB out of 280	280	280

What separates them

Where the two part company

Every source in the database that drives one of them drives the other. On power, the choice between these two changes nothing about what amplifier you need.

16 sources stay below the audible-hiss threshold with the FP3 but cross it with the FD15 (FiiO BTR11, FiiO K11 R2R, Lake People G103-S Mk II, 13 more).

280 of the 280 sources here reach 100 dB on both.

At the level you actually listen at

What each one needs from 80 to 105 dB

The FP3 is more demanding than 35% of the 567 non-electrostatic models in this database; the FD15 than 10%.

dB SPL	FD15 power	FD15 voltage	FP3 power	FP3 voltage
80	0.6 µW	4 mV	3.2 µW	11 mV
85	2.0 µW	8 mV	0.01 mW	19 mV
90	6.3 µW	14 mV	0.03 mW	34 mV
95	0.02 mW	25 mV	0.10 mW	60 mV
100	0.06 mW	45 mV	0.32 mW	0.11 V
105	0.20 mW	80 mV	1.0 mW	0.19 V

What drives both

The cheapest source that satisfies both

Source	Price	Headroom, FD15	Headroom, FP3	Output impedance	Noise
JadeAudio JA11	$20	26.8 dB	19.3 dB	0.5 Ω	1.7 µV
FiiO KA11	$29	35.0 dB	27.5 dB	0.7 Ω	1.7 µV
FiiO BTR13	$59	32.0 dB	24.5 dB	0.6 Ω	1.0 µV

Of the 280 sources here, 280 reach 100 dB on both. 55 of them also publish an output impedance low enough for both under the one-eighth rule and a noise figure that stays below the audible-hiss threshold with both.

The cheapest of the 55 is the JadeAudio JA11, at $20. It leaves 26.8 dB of headroom on the FD15 and 19.3 dB on the FP3, its output impedance is 0.5 Ω against a one-eighth limit of 4.00 Ω and 4.50 Ω, and its noise figure puts the hiss floor 8 dB and 16 dB below the 20 dB SPL this site treats as the point where a quiet room stops hiding it.

Try any other source.

Frequency response

What each sheet prints, and what it is worth

Model	As printed	Tolerance	Standard
FD15	10Hz-40kHz	not printed	not printed
FP3	10Hz-40kHz	not printed	not printed

FiiO prints the same thing for both the FD15 and the FP3: 10Hz-40kHz.

Neither range has a tolerance printed beside it, so the matching numbers say little.

Not a measurement; maker by maker.

Both pages in full

Both have a page of their own. In full: FiiO FD15 and FiiO FP3. Every figure on this page comes from what FiiO published, or is derived from it — what that maker publishes, counted.