The 55HK5600 is a 55 inch 4K TV from Hitachi, launched in the year 2021. It comes with a 10-bit IPS panel. The max. resolution it can achieve is 3840 x 2160 @ 60 Hz with a pixel density of 80 ppi.
Picture Quality
After screen size and resolution, the next most important feature of a display is its Color Reproduction Accuracy, which is defined by its color gamut specification.
Hitachi did not provide a color gamut rating for this TV. So we have to take a guess.
Now, since the TV features a big 55 inch screen, it won't come with a cheap panel, so here we can assume its equivalent sRGB coverage to be 90-100% or above. Undoubtedly The color quality on this TV should be Lifelike! It is capable of producing color accurate images.
Understanding Color Gamut
Color gamut spec of a display indicates the range of colors that it can produce.
A display with poor color accuracy will produce washed out colors that will not be pretty to look at.
It is specified in different units - sRGB(most popular), NTSC, DCI P3 etc.
But don't worry, below is a chart that you can use to choose a TV with good color accuracy.
Now, after color gamut, you should look at the static contrast specification as it influences the picture quality substantially.
What is Static Contrast ?
There are 2 types of contrast specifications for a TV. Static and Dynamic. We are interested in static contrast ratio as dynamic doesn't matter much.
Static contrast specification tells the intensity of black levels. That is, a TV with SC ratio less than 1000:1 may produce black images something like this:

Apart from this, such TVs may suffer from backlight bleeds that will impact your experience — as shown below.

Also note, static contrast ratio and resolution go hand in hand when it comes to details. To put it into perspective, a TV with low contrast ratio will produce less shades of colors, thus lesser detail overall.
If given a choice, always prefer a FHD TV with high contrast ratio over a 4K TV with low contrast ratio.
This TV features a static contrast ratio of 8000:1., well enough to achieve deep blacks and eye-catching visuals. For the record, it also comes with local dimming which is a plus.
HLG (Hybrid Log Gamma), HDR and HDR10 are also supported on this TV, so that's a plus.
Coming to brightness, the peak brightness it can produce is 250 nits with the help of Direct LED backlight.
Gaming Performance
If you are planning to use your TV only for content consumption, you can ignore these specifications. But if you are also going to use the TV for gaming or use it as a PC monitor, you would want to take a TV that features the lowest input lag and response time.
Sadly, there is no specification for input lag on this TV. Now, as this is not a cheap TV from Hitachi, input lag on this TV could be 20ms or below.
What is Input Lag and Why it matters ?
This lag is the latency at which inputs changes the content of your display. For casual Non-FPS games, input lag doesn't matter much.
But ideally, get a TV that comes with an input lag and response time of < 20ms.
Dimensions and Ergonomics
The width of this TV is 49 inches while its height is 29.46 inches. Overall the TV weighs around 13.0 KGs including its stand. Without stand, it weighs 10.5 Kilograms.
Speaking of ergonomics — VESA mount is supported on this TV with an interface size of 200 x 200 mm. The unit doesn't come with Swivel, Tilt or Pivot support.
Hardware and Audio
The TV is powered by 4-Core CPU. However, Hitachi didn't provide any info on the available RAM on the TV's official specsheet.
The Operating System on this TV is Android 10.
For display connectivity, Hitachi has provided two HDMI 2.0 (ARC; CEC) ports and one AV Composite In (Video + L/R) port on this TV.
For connecting USB devices, it includes one USB 2.0 port. Other connectivity ports include — 1x Satellite In (Main — F-type female), 1x AV Component In (YPbPr + L/R) (via PC input), 1x Antenna (RF) (female), 1x CI+ 1.4 and 1x Ethernet RJ45.
Wireless connectivity options on this TV include Wi-Fi (5Ghz + 2.5Ghz), Wifi-Direct, Bluetooth and DLNA.
The Audio unit of this TV is powered by 2 x 10W built-in speakers.
Now, coming to power usage, it uses 131.2 watts on average and 0.5 watts on standby.
It supports a power outlet of 220 V - 240 V/50 Hz - 60 Hz.