iFi ZEN Air Blue Bluetooth DAC Reviewed

The iFi ZEN Air Blue occupies a specific, high-value niche in the desktop audio landscape. While many manufacturers treat Bluetooth as a secondary convenience, iFi has engineered the Air Blue as a dedicated high-resolution bridge for those who demand high performance without wires.

But Bluetooth audio receivers are plentiful on the market, and there are many that incorporate high-resolution connectivity for half the price of the iFi, or less. What is so special about the Zen Air Blue?

It’s hard to say from the outside. The plastic casing feels premium enough and has a pleasing weight, though its fascia, held on by double-sided tape, did become detached when I pulled the protective plastic from the review sample. The front and ear panels are glossy plastic, prone to fingerprints and scratches.

Though the design mimics the more expensive Zen components, the Zen Air products replicate the design of the unibody aluminium enclosure in a two-part plastic shell, where you’d probably get an extruded aluminium body from a no-name brand for similar money. The Zen Air Blue is £99 in the UK.

The Zen Air Blue takes a Bluetooth input and sends it to a pair of RCA outputs. There are no digital outputs for connection to external DACs, nor digital inputs to use the internal DAC with another digital device. It’s designed to bring Bluetooth connectivity to an analogue amplifier, a pair of active speakers, a desktop headphone amp or even your old music centre.

All the current high-definition Bluetooth audio formats are supported; Qualcomm’s aptX Adaptive and aptX HD, Sony’s LDACTM and Huawei’s LHDC , regular aptX and aptX Low Latency, AAC (Apple iOS devices) and SBC (the ‘plain vanilla’ Bluetooth codec).

Among the 24-bit-capable codecs, aptX HD supports up to 48kHz, whereas aptX Adaptive, LDACTM, and LHDC can reach 96kHz. iFi’s ‘Bluetooth engine’ can also be updated over-the-air, so future codecs may be added in the future. Many of the cheaper, generic Bluetooth receivers claim codec support that they don’t necessarily deliver.

iFi claim their Bluetooth engine “avoids the
typical 40% quality drop found with
standard Bluetooth.” They don’t provide any objective measurements or data to support that figure, nor why their Bluetooth engine is special or differs from other implementations using the same Qualcom 5100-series chipset.

The DAC uses a discrete ESS Sabre Hyperstream DAC chipset, specially an ES9023, with time domain jitter eliminator, discrete oscillator and 112dB dynamic range. Extensive jitter-eradication technologies are applied to the digital stage, including iFi’s GMT (Global Master Timing) femto-precision clock and the intelligent memory buffer. Generic devices will typically use a cheaper chipset like the PCM5xx series. There’s nothing inherently wrong with that, but the ESS DACs are among the state of the art at the moment, and the ES9023 is just a trickled-down version with very respectable performance.

iFi claim their low-jitter crystal clock has been updated to provide >20dB better performance. TDK C0G (Class 1 ceramic) capacitors offer high stability and low losses for resonant circuit applications. Getting ever closer to the theoretical ideal of pure, frequency-constant capacitance, these capacitors reduce capacitor-induced distortion to vanishingly low levels.

Texas Instruments low-noise op-amps in the final output stage offer great unity-gain bandwidth, very low noise and distortion, high output drive capability, Common-mode and Power Supply Rejection Ratios of over 100 dB, wide maximum-output-swing bandwidths and high slew rates. Exactly which chips are being used I can’t tell you, as they are not specified anywhere and the means of disassembling the iFi’s plastic shell non-destructively isn’t immediately apparent. In reality, the old NE5532 would be fine in this application.

Specs are 109dB (A-weighted) signal to noise ratio at 0dBFS, and a 20Hz – 20kHz frequency response within +0/-0.5dB at 44.1kHz. Frequency response at 88.2kHz is a less impressive 1Hz – 44khZ, with a -3dB rolloff at frequency extremes. Total harmonic distortion is <0.0015% into a 10k load at 0dBFS; by no means state of the art, but inaudible.

The Zen Air Blue runs from a DC 5V power supply, capable of delivering 0.5A (2.5W). It includes a USB to DC power cable, though doesn’t include even a basic USB power supply. Given that iFi makes a ton of power solutions, arguably its core product, not including so much as a basic wall plug in the box is tight.

Using the device is simple. Status is indicated by colour-changing LEDs. The Bluetooth Sample Rate LED indicates the sampling frequency received by ZEN Air Blue from the music source – 44/48kHz Blue, 88/96kHZ White. The current codec is shown by the colour of the iFi logo in the centre of the front display – SBC off, AAC yellow, aptX blue, aptX HD magenta, aptX Adaptive green, aptX Low-Latency red, LDAC cyan, LHDC/HWA white.

Controlling the device is via a single button. The Zen Air Blue will remember up to eight previously paired devices, though only one may be connected at a time. It searches for the most recently paired device on power up, and if multiple paired devices are within range it defaults to the most recently used.

Short pressing the button will switch the display on or off. Pressing the button twice quickly toggles the spoken status announcements, on indicated by a high tone and off by a low tone.

Sonically the Zen Air Blue goes about as far as Bluetooth can, in terms of outright quality. Fed a quality digital file from a source that supports one of the high-resolution codecs, it is difficult to distinguish it from the same source directly into a similar, though not identical, wired DAC.

Comparative testing here is rather pointless since a proper test would require a DAC identical to that of the Zen Air Blue, capable of accepting a wired digital input, which I don’t have to hand. The Zen Air Blue is nowhere near achieving the theoretical 144dB dynamic range available in a 24-bit, 96kHz resolution stream, but no DAC on the market at any price currently is. In practical terms its specifications largely exceed the limitations of the input media, that being a Bluetooth source.

Even the 3dB rolloff as you approach 88.2kHz sampling rates is of no concern. 16-dit, 44.1kHz audio (the original compact disc specification) offers a bandwidth of just over 22kHz, 2kHz above the top of the audio band.

The Zen Air Blue is measurably flat to within 0.05dB from 20Hz to 20kHz, which is by no means state of the art digital performance but it is beyond the limits of our ears to detect audible deviations in level. It sounds neutral to the source, audibly quiet and without obvious distortion, exactly as the specifications tell us it should.

Given that the Zen Air Blue will primarily be used to stream content from portable devices, likely from streaming services such as Spotify, Apple Music or internet radio, it is likely the content you stream will be lossless at source. Even if you do stream a high-res track, current Bluetooth codecs are so good that I’d challenge anyone to tell the difference between a Bluetooth connection and a wired one, especially if you aren’t critically listening. As is true for much in the subjectivist-lead audio world, there have been no proper controlled tests to determine whether Bluetooth has in fact not reached a point where it is not only a convenient streaming solution, but a perfectly valid one where audio quality is a concern.

Regardless, the Zen Air Blue offers support for the latest codecs in a neat package, with potential for future upgrades in software as new codecs become available. They could include a power supply for £99, but when a £1200 smartphone or a 6 grand laptop from a fruit-flavoured tech firm doesn’t, who can blame them? It’s a brilliant device, ideal if you want to add Bluetooth streaming to an older, analogue setup, or dd some casual convenience to your high-end hi-fi. Highly recommended.