ddHiFi TC44 Pro E2 vs HiBy FC4

Short answer

More power: the ddHiFi TC44 Pro E2, with 250 mW into 32 Ω; the HiBy FC4 has 110 mW. The ddHiFi TC44 Pro E2 drives 4 headphones to 100 dB that the HiBy FC4 cannot (Moondrop COSMO, Symphonium Crimson, Symphonium Helios, 1 more).
Hiss with sensitive IEMs: cannot be compared — the maker of the ddHiFi TC44 Pro E2 publishes no noise figure.
Price: the same, $99.

Both are dongles, both at $99.

The ddHiFi TC44 Pro E2 reaches 100 dB on 565 of the 567 models here, the HiBy FC4 on 561.

Side by side

Every published figure, next to each other

Specification	ddHiFi TC44 Pro E2	HiBy FC4
Power into 32Ω	250 mW	110 mW
Power into 150Ω	53 mW	23 mW
Power into 300Ω	27 mW	12 mW
Power into 600Ω	13 mW	5.9 mW
Output impedance	not published	not published
Output noise	not published	1.7 µV
Price	$99	$99
Headphones it reaches 100 dB on out of 567	565	561

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	ddHiFi TC44 Pro E2	HiBy FC4
Socket	no separate rating	4.4mm
Power into 32Ω	—	340 mW
Power into 300Ω	—	36 mW derived
Output impedance	—	not published
Output noise	—	2.2 µV
Headphones it reaches 100 dB on out of 567	—	565

Only the HiBy FC4 has a separate balanced rating from its maker; through it, it reaches 100 dB on 565 of the 567 models here. The ddHiFi TC44 Pro E2 may still have a balanced socket — its spec sheet simply gives no figure for one, so there is nothing to put beside it. Derived figures are worked out from the loads the maker did publish.

How solid these numbers are

Where each power figure comes from

Load	ddHiFi TC44 Pro E2	HiBy FC4
32 Ω	Published	Published
150 Ω	Derived	Derived
300 Ω	Derived	Derived
600 Ω	Derived	Derived

Both makers publish a power rating. ddHiFi TC44 Pro E2 publishes at 32 Ω; HiBy FC4 at 32 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.

What separates them

The headphones that tell them apart

4 headphones reach 100 dB on the ddHiFi TC44 Pro E2 but not on the HiBy FC4 — Moondrop COSMO, Symphonium Crimson, Symphonium Helios, 1 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 Sennheiser HD 600: ddHiFi TC44 Pro E2 has +6 dB of headroom there against +2 dB. 4 dB is about 2.3 times the power, which matters for peaks rather than for how loud the music sits.

The hiss columns are empty for ddHiFi TC44 Pro E2 because that maker publishes no output noise figure.

Headphone	Impedance	Needs	ddHiFi TC44 Pro E2 headroom	HiBy FC4 headroom	ddHiFi TC44 Pro E2 hiss	HiBy FC4 hiss
Shure SE846	9 Ω	0.04 mW	+32 dB	+29 dB	not published	19 dB
Campfire Audio Andromeda 2020	9 Ω	4.0 mW	+12 dB	+9 dB	not published	-1 dB
Audeze LCD-2 Classic	70 Ω	0.79 mW	+22 dB	+18 dB	not published	-3 dB
Beyerdynamic DT 1990 Pro (250Ω)	250 Ω	0.63 mW	+17 dB	+13 dB	not published	-7 dB
HiFiMAN HE400se	25 Ω	7.9 mW	+14 dB	+10 dB	not published	-8 dB
Audio-Technica ATH-R70X	470 Ω	1.6 mW	+10 dB	+7 dB	not published	-14 dB
Sennheiser HD 600	300 Ω	6.6 mW	+6 dB	+2 dB	not published	-18 dB
HiFiMAN Susvara	60 Ω	50 mW	+4 dB	+1 dB	not published	-20 dB

What the price difference buys

The gap in dollars, against the gap in numbers

These two cost the same, $99, so price settles nothing. Out of the 567 models here, the ddHiFi TC44 Pro E2 drives 4 models to 100 dB — and on the other side there is no such advantage at all.

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

Each in full: ddHiFi TC44 Pro E2 and HiBy FC4.