The world's slimmest smartphone is now 4.75mm thick

How thin is too thin? Well, the Chinese smartphone makers are always pushing their limits on this end. Following Gionee's 5.1mm Elife S5.1 and Oppo's 4.85mm R5, today Vivo has set a new record with its X5Max, a 4.75mm-thick Android phone that still manages to pack a number of notable features. The slim aluminum mid-frame houses a vibrant 5.5-inch 1080p Super AMOLED screen, a 1.7mm-thick logic board and a 5-megapixel f/2.4 front camera. Flip to the back and you'll find a 13-megapixel f/2.0 main camera -- the inevitable bulge that goes beyond the phone's official thickness by almost 2mm -- and a loudspeaker towards the bottom. On the whole, the phone feels surprisingly light (Vivo has yet to list the official weight) but also solid and well-made.

It's worth pointing out that unlike the Oppo R5, the X5Max has managed to keep its 3.5mm headphone jack instead of forcing a micro-USB adapter upon us. Another equally impressive feature is the dual-SIM tray (fits one Micro SIM and one Nano SIM) that also lets you use a microSD card (up to 128GB) in place of Nano SIM, but you might have already seen this on the likes of the Lenovo Vibe Z2 Pro or the Huawei Ascend Mate 7.

The X5Max is powered by a Qualcomm Snapdragon 615 chip that's both octa-core (quad 1.7GHz Cortex-A53 and quad 1GHz Cortex-A53) and 64-bit ready, though the latter part won't be usable until the phone is updated from Android 4.4.4 to Lollipop. You also get 2GB of RAM and 16GB of internal storage to boot, while the fixed 2,000mAh battery should be sufficient for a full-day usage; though you'll miss out on the Oppo R5's awesome rapid charging technology.

Like its sibling devices, the X5Max places heavy emphasis on its audio performance, which is why it packs some dedicated audio chips -- Yamaha YSS-205X signal processor, Sabre ES9018K2M DAC, exclusive Sabre ES9601 headphone amplifier and OPA1612 amplifier -- as part of its "Hi-Fi 2.0" package. Together, these apparently outperform the Xplay3S' offering in terms of signal-to-noise ratio, dynamic range and restoration. More importantly (for this author, at least), the Yamaha chip is actually for implementing a karaoke mode, in which you can sing along with songs and music videos while also hearing yourself -- with added echo or reverb if desired -- through headphones. It may be gimmicky for some, but apparently it's also what the cool kids like to use these days.

Alas, the X5Max is only launching in China to begin with: The China Mobile version will be available for CN¥2,998 or about US$490 as of December 12th. As for those outside China who need a phone to quench their karaoke thirst, stay tuned for an FDD-LTE version later.