Panasonic TX-40CX680B review

Firefox OS stars on this customisable 4K TV that easily makes its pixels plausible

Panasonic TX-40CX680
40-inch affordable Firefox 4K

TechRadar Verdict

4K at 40-inches? This nicely priced LED with Firefox OS makes use of its eight million pixels by boosting black levels, colour and upscaling prowess to make everything save for standard definition look sumptuous. With Freeview Play incoming, it's an early 4K bargain.


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    Colours & black levels

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    4K detail

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    Customisable Firefox OS

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    Freeview Play incoming


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    Soft standard-def

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    Firefox OS lacks content

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    Three HDMI

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    No 3D

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4K versus Full HD; can you tell the difference?

4K is all about huge TVs, it's about sitting closer to the TV and it's about coming face-to-face with an eight megapixel TV image instead of two megapixels.

That's the maths behind the 3840x2160 pixels of 4K material, but what happens if everything – including the price – is shrunk down to 40-inches?

That's a conundrum tackled head-on by the Panasonic TX-40CX680B, comfortably the smallest 4K TV to be reviewed so far. At £669, it's also one of the very best value, with an all-new Firefox OS and Freeview Play adding to the package.

However, it's not the best-looking.

It's 47mm in depth with a 10mm gloss black bezel around three sides and 18mm across the bottom tapering backwards. Compact and serious-looking, it's another business-like design from Panasonic.


On the Panasonic TX-40CX680B the all-new Firefox OS, which forms the basis for an all-new version of Panasonic's my Home Screen smart TV user interface, is making its debut. Just as enticing is that it's all powered by a Quad-Core Pro processor, which ought to make it easy to navigate and quick to load apps.


Its other characteristics and features are fast moving from the 'wants' to the 'needs' list; LED local dimming, a Freeview HD tuner and Wi-Fi. However, there is one expected feature missing from the TX-40CX680B - 3D.

Whether or not that will trouble anyone though is doubtful.

Aside from Firefox OS, the key new features are with the LED panel itself; a newly developed LED backlight and Wide Colour Phosphor tech claim to produce more than 90% of DCI (Digital Cinema Initiatives) standards for movie directors, though it's local dimming that's much more important.

However, HDR is nowhere to be seen.

Surely one of the biggest must-haves about the TX-40CX680B is Freeview Play, though sadly it wasn't quite ready at the time of this review.

Already at the centre of the Firefox OS is a Freeview Play Catch-Up app, though Freeview Play itself is not expected to appear on the TX-40CX680B (and all UK models of Panasonic TVs at its level and above) until later this summer.



Though the strength of the new Firefox OS isn't really about apps, there's a decent choice nonetheless.

Netflix, Amazon Instant, YouTube, AccuWeather and the BBC iPlayer all appear on the default home screen, with an online store adding hundreds of others from Facebook, Dailymotion and BIGFlix to TuneIn, Deezer, Eurosport Player, Picasa, BharatMatrimony, Al Jazeera, CNBC Real-Time, Meteonews TV, Withings, Bild, CineTrailer, Rovi Guide, HappyTrips and dozens more.

The TX-40CX680B also has a HEVC decoder so is compatible with 4K content from Netflix and Amazon Instant.


Ins & outs

Despite the low price the TX-40CX680B is packed with inputs and outputs.

On the rear is a RGB Scart (though to use such an old-fashioned standard definition-only connection would almost be criminal), component video slots, and a set of left and right phonos. Directly underneath are two down-facing HDMI inputs alongside a wired LAN slot, an optical digital audio output, and an RF slot to power the Freeview HD tuner.

A side panel adds a headphones jack, a Common Interface slot, and a third HDMI input, though that's perhaps one short for many living rooms. However, all the HDMIs are compatible with HDCP 2.2 for Ultra HD Blu-ray, and there's no such complaint about the side panel's three USB slots.

Also available

The 40-inch TX-40CX680B is the smallest in Panasonic's UK-only CX680 Series, which all include the Firefox OS and Freeview Play. The other two sizes available are the 50-inch TX-50CX680B and 55-inch TX-55CX680B.

It's only when you drop down to the CS500 Series (as with the TX-32CS510) that you lose Firefox, and Freeview Play is replaced by Freetime.

Jamie Carter

Jamie is a freelance tech, travel and space journalist based in the UK. He’s been writing regularly for Techradar since it was launched in 2008 and also writes regularly for Forbes, The Telegraph, the South China Morning Post, Sky & Telescope and the Sky At Night magazine as well as other Future titles T3, Digital Camera World, All About Space and He also edits two of his own websites, and that reflect his obsession with travel gear and solar eclipse travel. He is the author of A Stargazing Program For Beginners (Springer, 2015),