FiiO K17 vs FiiO K9 Pro: Which Drives More Headphones?

FiiO K17 vs FiiO K9 Pro

Short answer

Power: about the same. The FiiO K17 has 1.85 W into 32 Ω, the FiiO K9 Pro 2.00 W (balanced: 4.00 W and 2.00 W). Both drive 567 of the 567 non-electrostatic headphones here to 100 dB, so on that test the difference changes nothing.
Quieter with sensitive IEMs: the FiiO K9 Pro. 55 headphones stay below audible hiss on it but not on the FiiO K17 (64 Audio Nio, 64 Audio U12t, 64 Audio U18s, 52 more).
Price: the FiiO K9 Pro costs $191 less and gives up nothing on power, output impedance or hiss against the 567 headphones here. Whatever the extra money for the FiiO K17 buys, it is not these three numbers.

Both are desktop DAC/amps, $990 against $799.

On raw power they are level: each reaches 100 dB on 567 of the 567 non-electrostatic models here.

Specification	FiiO K17	FiiO K9 Pro
Power into 32Ω	1.9 W	2.0 W
Power into 150Ω	431 mW	482 mW
Power into 300Ω	240 mW	278 mW
Power into 600Ω	120 mW	139 mW
Output impedance	1.0 Ω	1.0 Ω
Output noise	5.0 µV	2.0 µV
Price	$990	$799
Headphones it reaches 100 dB on out of 567	567	567

Specification

FiiO K17

FiiO K9 Pro

Power into 32Ω

1.9 W

2.0 W

Power into 150Ω

431 mW

482 mW

Power into 300Ω

240 mW

278 mW

Power into 600Ω

120 mW

139 mW

Output impedance

1.0 Ω

Output noise

5.0 µV

2.0 µV

Price

$990

$799

Headphones it reaches 100 dB on
out of 567

567

The 4.4 mm or XLR socket, rated on its own

Balanced	FiiO K17	FiiO K9 Pro
Socket	4.4mm / XLR4	4.4mm + XLR4
Power into 32Ω	4.0 W	2.0 W
Power into 300Ω	950 mW	1.1 W
Output impedance	1.5 Ω	1.0 Ω
Output noise	7.9 µV	3.0 µV
Headphones it reaches 100 dB on out of 567	567	567

Through the balanced sockets the two are level on the same test: each reaches 100 dB on 567 of the 567 models here.

Where each power figure comes from

Load	FiiO K17	FiiO K9 Pro
32 Ω	Published	Published
150 Ω	Derived	Derived
300 Ω	Published	Published
600 Ω	Derived	Derived

Both makers publish a power rating. FiiO K17 publishes at 32 Ω and at 300 Ω; FiiO K9 Pro at 32 Ω and at 300 Ω. The other rows are worked out from those.

The two publish at the same loads, which is the one case where the rows of this table can be read straight across.

What the labels mean.

The headphones that tell them apart

On power they are interchangeable across this whole database: there is no headphone here that one reaches 100 dB on and the other does not.

55 headphones stay below the audible-hiss threshold on the FiiO K9 Pro but cross it on the FiiO K17 (64 Audio Nio, 64 Audio U12t, 64 Audio U18s, 52 more).

567 of the 567 models here reach 100 dB on both.

Headroom and hiss on 8 models, both sources

Headroom is at a 100 dB SPL peak.

The widest gap on the list is the Shure SE846: FiiO K17 has +44 dB of headroom there against +42 dB. 2 dB is about 1.6 times the power, which matters for peaks rather than for how loud the music sits.

Hiss below about 20 dB SPL is inaudible in a quiet room.

Headphone	Impedance	Needs	FiiO K17 headroom	FiiO K9 Pro headroom	FiiO K17 hiss	FiiO K9 Pro hiss
Shure SE846	9 Ω	0.04 mW	+44 dB	+42 dB	28 dB	20 dB
Campfire Audio Andromeda 2020	9 Ω	4.0 mW	+24 dB	+22 dB	8 dB	0 dB
Audeze LCD-2 Classic	70 Ω	0.79 mW	+30 dB	+31 dB	7 dB	-1 dB
Beyerdynamic DT 1990 Pro (250Ω)	250 Ω	0.63 mW	+26 dB	+27 dB	2 dB	-6 dB
HiFiMAN HE400se	25 Ω	7.9 mW	+24 dB	+23 dB	1 dB	-7 dB
Audio-Technica ATH-R70X	470 Ω	1.6 mW	+20 dB	+20 dB	-5 dB	-13 dB
Sennheiser HD 600	300 Ω	6.6 mW	+16 dB	+16 dB	-9 dB	-17 dB
HiFiMAN Susvara	60 Ω	50 mW	+13 dB	+13 dB	-11 dB	-19 dB

The gap in dollars, against the gap in numbers

The FiiO K17 costs $191 more than the FiiO K9 Pro, and on these three axes the money buys nothing: among the 567 models here there is not one that the FiiO K17 handles and the FiiO K9 Pro does not — not on power, not on the one-eighth rule, not on hiss. The traffic runs the other way: the cheaper FiiO K9 Pro keeps 55 models below the audible-hiss threshold that the FiiO K17 does not.

Only published figures count here; blank axes are counted separately.