Disclaimer: Astell&Kern supplied the XB10 used in this small performance essay free of charge. I will be writing more about it at Headfonia in the coming weeks. It goes for 189,00$. You can find out all about it here: Extreme Bluetooth AK XB10.
At the top of every every audiophile’s wish list should be the democratisation of headphone output performance. Think Chord Mojo, Theorem 720, ALO Continental. For good reason - hiss, poor output impedance, connection problems, and general shyte performance - Bluetooth DAC/amps rarely make the cut.
And while the XB10 is a Bluetooth DAC/amp, it doesn’t deserve to be lumped in with the competition. Not only does it approach the selective measurable audio performance of modern smartphones, it does so with the added bonus of a balanced output. It shows load effect in line with an iPhone 6, but manages stereo crosstalk scores the iPhone can’t touch. Even under load, it maintains noise levels of ~-109dB and dynamic range of ~96dB. High-ohm headphone users will note that it also kicks out volume levels similar to an iPhone 6- that is, unless you make use of its balanced out, which is more powerful. Under load, both maintain respectable signals.
Two quirks mar the XB10: the hiss it outputs into even middling sensitive earphones is much higher than any respectable smartphone or audiophile DAP. They are, in fact, higher than the original AK100, which I consider the upper limit of acceptability for audiophile devices. High-volume listeners likely won’t be bothered by it even through sensitive earphones. Headphone users won’t be bothered at all. Low-volume listeners like me will hear it through sensitive earphones at all volumes, all the time. The other issue is that loaded or not, base THD and IMD levels are extreme. I doubt that they will mar the listening experience for most audiophiles, but they are audible when reviewing metric-based test files, and test many hundreds of times higher than usual.
Nevertheless, the XB10 is a Bluetooth DAC/amp. Audible provisos are a given. And for less than 200$, for a device that cuts the wires, and adds a powerful balanced output, the XB10 impresses. Interestingly, Astell&Kern’s DAPs are next to useless with the XB10. The AK70 never connects reliably, only shakily managing connection distances of up to a metre. The AK100 and AK Jr, similarly and deplorably maintain weak connections. You could argue that the XB10 duplicates base functionality of A&K’s latest DAPs, and is therefore unnecessary. But in situations where you neither need, nor desire wires, it is a shame that your precious A&K is next to useless with the XB10.
Is this poor marketing/design on A&K’s part, or is the XB10’s incompatibility with AK DAPs a calculated gambit to toehold the smartphone audiophile market?
Source: iPhone 6
ADC: Lynx Studio HILO LT-TB
Computer: MacBook Pro 21015; 2012 27" iMac
Cables: 1,5m Hosa Pro 3,5mm stereo to dual 3-pin XLR (around 8$)
Loads: measured at +0dB @volume levels matched to iPhone 6 max output (SE: max, BAL ~90%)
NL - no load
SM2 - Earsonics SM2
Orion - Campfire Audio Orion
ES7 - Audio Technica ES7
DT880 - Beyerdynamic DT880
24-bit single ended (SE) TARGETS and loads
24-bit balanced (BAL) TARGETS and loads
Assuming that you’ve got a phone (or plastic DAP) in your hand, the XB10 adds functionality you won’t find in DAPs costing less than 500$, and weighing as much as your phablet. It democratises the performance of your headphones across all devices to which it connects. It hisses more than it should. Base IMD levels are rude, but when the music gets going, I imagine that 99% of so-called audiophiles won’t notice a thing. It approaches the performance of a good smartphone in several key areas, but is in no way its equal across all metrics. And yet it is Bluetooth. And in that space, it is a remarkable device that Astell&Kern will be remembered for having created.