Astell&Kern HC3 vs FiiO KA17

Short answer

Power: about the same. The Astell&Kern HC3 has 125 mW into 32 Ω, the FiiO KA17 140 mW. The FiiO KA17 drives 3 headphones to 100 dB that the Astell&Kern HC3 cannot (Moondrop COSMO, Symphonium Helios, Symphonium Zenith).
Hiss with sensitive IEMs: cannot be compared — the maker of the Astell&Kern HC3 publishes no noise figure.
Output impedance: 74 headphones are left alone by the FiiO KA17 under the one-eighth rule but coloured by the Astell&Kern HC3 (64 Audio Aspire 1, 64 Audio Fourte, 64 Audio Ocean, 71 more).
Price: the FiiO KA17 costs $30 less, and wherever both makers publish a figure the Astell&Kern HC3 shows no advantage for the extra money.

Both are dongles, $179 against $149.

The FiiO KA17 reaches 100 dB on 564 of the 567 models here, the Astell&Kern HC3 on 561.

Side by side

Every published figure, next to each other

Specification	Astell&Kern HC3	FiiO KA17
Power into 32Ω	125 mW	140 mW
Power into 150Ω	27 mW	34 mW
Power into 300Ω	13 mW	20 mW
Power into 600Ω	6.7 mW	10.0 mW
Output impedance	2.0 Ω	1.0 Ω
Output noise	not published	2.0 µV
Price	$179	$149
Headphones it reaches 100 dB on out of 567	561	564

Not published means the maker leaves it out, so that axis cannot be compared.

Balanced output

The 4.4 mm or XLR socket, rated on its own

Balanced	Astell&Kern HC3	FiiO KA17
Socket	no separate rating	4.4mm
Power into 32Ω	—	300 mW
Power into 300Ω	—	30 mW
Output impedance	—	1.5 Ω
Output noise	—	2.2 µV
Headphones it reaches 100 dB on out of 567	—	565

Only the FiiO KA17 has a separate balanced rating from its maker; through it, it reaches 100 dB on 565 of the 567 models here. The Astell&Kern HC3 may still have a balanced socket — its spec sheet simply gives no figure for one, so there is nothing to put beside it.

How solid these numbers are

Where each power figure comes from

Load	Astell&Kern HC3	FiiO KA17
32 Ω	Upper bound	Published
150 Ω	Upper bound	Derived
300 Ω	Upper bound	Published
600 Ω	Upper bound	Derived

These two columns are not the same kind of number, and that matters more than the gap between them. FiiO KA17 publishes a power rating (at 32 Ω and at 300 Ω); Astell&Kern HC3 publishes no power figure at any load, only a maximum output voltage, so every milliwatt in its column is a ceiling worked out from that voltage.

A ceiling assumes the amplifier holds that voltage into the load, and nothing on Astell&Kern HC3’s own sheet says it does. It is the most flattering reading available, and it is used here only because the alternative is a blank. Where the Astell&Kern HC3 column looks the stronger of the two, treat the difference as unproven rather than measured. 24 of the 280 sources here are in that position, with no published power rating at any load.

What the labels mean.

What separates them

The headphones that tell them apart

3 headphones reach 100 dB on the FiiO KA17 but not on the Astell&Kern HC3 — Moondrop COSMO, Symphonium Helios, Symphonium Zenith.

74 headphones are left alone by the FiiO KA17 under the one-eighth rule but coloured by the Astell&Kern HC3 (64 Audio Aspire 1, 64 Audio Fourte, 64 Audio Ocean, 71 more).

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

On real headphones

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 KA17 has +32 dB of headroom there against +29 dB. 2 dB is about 1.8 times the power, which matters for peaks rather than for how loud the music sits.

The hiss columns are empty for Astell&Kern HC3 because that maker publishes no output noise figure.

Headphone	Impedance	Needs	Astell&Kern HC3 headroom	FiiO KA17 headroom	Astell&Kern HC3 hiss	FiiO KA17 hiss
Shure SE846	9 Ω	0.04 mW	+29 dB damping	+32 dB	not published	20 dB
Campfire Audio Andromeda 2020	9 Ω	4.0 mW	+9 dB damping	+12 dB	not published	0 dB
Audeze LCD-2 Classic	70 Ω	0.79 mW	+19 dB	+19 dB	not published	-1 dB
Beyerdynamic DT 1990 Pro (250Ω)	250 Ω	0.63 mW	+14 dB	+16 dB	not published	-6 dB
HiFiMAN HE400se	25 Ω	7.9 mW	+11 dB	+12 dB	not published	-7 dB
Audio-Technica ATH-R70X	470 Ω	1.6 mW	+7 dB	+9 dB	not published	-13 dB
Sennheiser HD 600	300 Ω	6.6 mW	+3 dB	+5 dB	not published	-17 dB
HiFiMAN Susvara	60 Ω	50 mW	+1 dB	+2 dB	not published	-19 dB

What the price difference buys

The gap in dollars, against the gap in numbers

The Astell&Kern HC3 costs $30 more than the FiiO KA17, and on these three axes the money buys nothing: among the 567 models here there is not one that the Astell&Kern HC3 handles and the FiiO KA17 does not — not on power, not on the one-eighth rule, not on hiss. The traffic runs the other way: the cheaper FiiO KA17 drives 3 models to 100 dB and leaves 74 alone under the one-eighth rule that the Astell&Kern HC3 does not.

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

Both pages in full

Each in full: Astell&Kern HC3 and FiiO KA17.