“Man, I wish I could rip off the bottom centimetre of my phone and replace it with a tiny gadget that gives me better sound,” said very few people ever. But now you can anyway.

The LG G5 is 2016's most innovative smartphone, and the reason for that is because you can upgrade it with modular components. We've already tested the Cam Plus, which adds extra battery life and camera controls, and now it's the turn of the LG Hi-Fi Plus with B&O Play.

Yes, it’s a clunky name, so let’s break it down: LG has partnered with Danish audio experts Bang & Olufsen to make a DAC that promises to bring hi-fi quality sound to your phone.

That may not sound very important, but believe us it is. 

Focus pocus

To understand why it matters, you need to know what a DAC is. Well, it stands for digital-to-analogue converter and a DAC's job is to take the digital ones and zeroes on your SD card and turn them into the analogue signal your headphones need to sing.

The LG G5 (and every other smartphone) already has a built-in DAC, but the Hi-Fi Plus module overrides it. There are a few reasons why you might want it to do that.

For starters, it's packing the kind of innards you'd find on proper hi-fi equipment, in the form of a ES9028C2M processor + Sabre9602C headphone amplifier. It supports music up to 32-bit/384kHz, and is more capable than the phone’s built-in 24-bit DAC.

Then there’s optimisation. A circuit designed for one job is will do that job better than a multi-tasker. Smartphones have been compared to Swiss Army knives, which is fair, but you wouldn’t use one to cut pizzas. The Hi-Fi Plus module can’t take pictures or play games, but it sure knows how to handle music properly.

Finally, isolation. There’s a lot happening on a phone’s circuit board. Even without you cluttering it up with your food pictures, it's constantly doing things with Wi-Fi, Bluetooth, the display and so on - and that can cause electrical interference. It’s better to have an entirely separate circuit: imagine doing your homework at the dinner table, versus having your own desk with nobody to point at the spinach in your teeth.

All about that base

So how does the module work? You remove the LG G5’s base and pull out the battery; next, attach the battery to the Hi-Fi Plus; finally, you slot it back in. And that’s it.

Your phone now has a new chin, about 1cm longer and covered in black rubbery plastic. Like Ben Affleck, but happier. It has the same extras as the standard chin – a speaker grille, a microphone and a USB-C port – and adds another headphone socket. You’ll need to plug into this before the module activates.

Do so and a little logo will pop up in the notification bar indicating that you’re good to go. The sound settings menu now has an extra option letting you adjust left-right balance, but otherwise it’s business as usual.

Meet the best-sounding phone in the world

And by ‘as usual’ we mean ‘with 100% more toe tapping’, because the Hi-Fi Plus puts the default audio performance to shame. The LG G5 already sounded pretty good, but with the module hooked up tunes sound a lot more clean and detailed, with a wider sense of space and a clearer idea of where instruments go. The tonal balance holds strong and dynamic impact is harder than your best Shoryuken.

Apple’s iPhone 6s is one of the best-sounding phones around, but by comparison it seems like a blunt instrument. Which makes the LG G5 and Hi-Fi Plus the best- sounding phone out there.

The DAC can take hi-res audio files up to 32-bit/384kHz, but you don’t need that to hear a difference; you’ll get better sound no matter whether you're feeding it CD-quality WAVs or listening to MP3-quality tracks on Spotify.

Flawed genius

See the top bit of the Hi-Fi Plus? Don’t lose it, because that’s not just a cap. It has its own USB-C port. Why? Because when you put the two pieces together, it can act as a standalone DAC for computers.

Unfortunately, here we found the first chink in the Hi-Fi Plus' armour. While it did improve the sound of the Macbook Air we tested it with, the difference wasn’t anywhere near as drastic as it was on the LG G5. But more worryingly, we encountered a bug that only let us listen to music at very high or very low volumes.

Hopefully this is something that can be fixed with a simple firmware update, but right now we'd only recommend it as a DAC for your phone. 

The other negative point here is the price. At £150 (RM830) it's not expensive for a proper standalone DAC: these can easily set you back hundreds or even thousands of pounds. But portable DACs are available in the RM300-500 range and while they don't match the Hi-Fi Plus for sound quality, they can be used on more than just one phone.

LG Hi-Fi Plus with B&O Play verdict

The Hi-Fi Plus is the very definition of a niche product. Sure, listening to music is a universal thing, but not many people will pay £150 (RM830) for the privilege of improving the sound quality on their phone. And the sub-set of those people who are also LG G5 owners will be even smaller.

If you do meet those two criteria then you're going to want one of these: it massively improves the sound of your music and is incredibly simple to use. The bug we encountered using it as a standalone is enough to deny it the full 5 stars, but if the Hi-Fi Plus shows us anything, it’s that modular phones have the potential to be totally badass. 

Stuff says... 

LG Hi-Fi Plus with B&O Play review

If you own a G5, really love music and can stomach the cost then it's a must
Good Stuff 
Amazing sound
Easy to use
Bad Stuff 
Makes the phone longer
Some issues with use as a standalone
Bit pricey