AirFly Pro adds BT to 3.5mm analogue devices

The AirFly Pro is a 3.5mm analogue to Bluetooth adaptor but even better as it can work both ways (not both at once).  Tx adds BT to any 3.5mm sound source, and Rx adds Bluetooth to any 3.5mm AUX Input.

Initially designed for Apple devices – it does work with most other BT device brands.

Airfly Pro

• Website here
• Manual here (it is PDF so check downloads folder)
• Price: Under $80 from JB Hi-Fi, Officeworks and online.
• Warranty: 1-year

Note: This is the only deep-dive review we can find on the web that has formally tested this device. The rest are regurgitations of press releases and most contain gross inaccuracies!

To understand the need for AirFly Pro you need to look at some use cases.

It has up to 16-hour USB-C cable (no charger supplied) rechargeable battery, but you can also use it when charging. Battery life is not a huge issue but it does reduce somewhat under certain circumstances. There are also other AirFly models.

In Tx (transmit) mode

• It can turn an old PC, amplifier, TV, iPod or transistor radio into a BT Tx device. Plug it into the 3.5mm socket (or 6.5mm headphone socket with an adapter) and up to two BT, 4.2 or later audio devices can attach. Note it assumes the analogue output is from 4-50 Ohms.
• Use it with a dual-pin aeroplane adaptor to use BT headphones in flight
• Use your car’s headphone jack to give BT audio connection
• Connect up to  two BT headphones/speakers from a TV (great for hearing impaired)

In Rx (receive) mode

• Update an old amplifier or amplified speaker (must have 3.5mm Aux-In) to BT
• It is either Tx or Rx – not both so you can’t use a handsfree microphone/headphone

A few tech things to consider

The makers twelvesouth tend to follow Apple tradition, and there are no real specs anywhere – more marketing hype!

A quick check of the FCC ID shows that the device uses a standard implementation of the Qualcomm CSR8670 Bluetooth Audio SoC. It is widely used in the value end of BT speakerphones, stereo speakers, headphones, earphones/buds, soundbars and most Bluetooth Tx/Rx dongles just like this one. So, the specs and limitations apply to all devices using this common SoC.

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It has (all on the one chip)

• Bluetooth 5.0+EDR (Enhanced Data Rate over shorter distances – not Bluetooth Low Energy BLE)
• Half-duplex (one-way at a time) Tx or Rx radio
• Stereo 16-bit/48kHz ADC (converts analogue 3.5mm signal to digital BT in Tx mode)
• Stereo 16-bit/96kHz DAC (converts digital BT signal to analogue 3.5mm in Rx mode)
• 200mA battery charger (can be up to 500mA with extra circuitry)
• 16MB memory and various audio and hardware interfaces
• Backwards compatible with recent BT 4.2 but not any device that needs a ‘pin code’ to connect
• It does not have any signal or volume amplification or gain.

The SoC supports both SBC and AAC codecs and optionally Qualcomm True Wireless, aptX/LL, Apple MFi and ANCS for iOS devices. It is up to device makers to enable these chip capabilities.

So, what does all that mean?

Our tests verify the base capabilities of the CSR8670 SoC.

• First and most importantly is GIGO – garbage in/garbage out. If your input signal (analogue) is weak, scratchy, static, distorted or low volume, then the AirFly Pro will faithfully transmit GIGO! In our tests, when used with an old transistor radio and TV, it was appalling. It was far better on a portable CD Walkman and car audio.
• The range (claim) is ten metres from the device, but in our tests, it was closer to two metres (that explains why it uses shorter range BT5.0+EDR).
•  We can’t accurately measure data transfer rates, but it uses the SBC or AAC codec, and we suspect it is between 96-128kbps/16-bit equivalent to MP3 radio quality
• We cannot find any way to enable the aptX or aptX LL (low latency – you can read about BT codecs here)
• Transmission strength is 0.1mW (for the shorter EDR distance)
• There is no signal gain or volume control, so it depends on the original device output and the amplification of the BT device, e.g. if there is a weak signal to start it will be weak and easily distorted in headphones.

Sound quality

• Two headphones (audio sharing) share the same bandwidth, and that impacts overall volume, sound quality and battery life. Volume is about half the wired volume.
• Sound quality (using our test Sennheiser headphones) is average and reduced again when two are attached.
• Gamers beware – latency is with around 150-175ms – far too high for a quick response. Video buffs – you may find lip-sync issues, especially with two headphones attached.
• We used it in Tx mode with a single headphone, and it got eleven hours and six with two headsets. Recharge time is about two hours from a 5VC/1A USB-A port.
• Once paired, you may need to clear the pairing to use BT devices again elsewhere.
• You need to turn it off manually, and there is no battery level indicator.
• In Rx mode, the AUX-In feed is not clean enough for audiophile use but fine for low-res audio content streaming.

And note the possible issue (as yet unsolved)

“Some customers may notice a lower volume using AirFly Bluetooth Transmitters with their AirPods or AirPods Pro if their AirPods have been updated to the latest Apple Firmware: 2A364 for AirPods 2nd Gen or 2B584 for AirPods Pro, respectively. We are actively investigating this issue with Apple and will provide an update as soon as possible.”

GadgetGuy’s take – fine if you don’t expect audiophile performance

First, let’s apologise to twelvesouth. AudioFly Pro is a decent product and fit for purpose – to add BT Tx or Rx to a non-BT device.

But frankly, there is little if any difference between it and the plethora of BT dongles using the CSR8670 SoC that start from about $20.

On the bright side, you are buying a known brand backed by Australian Consumer Law warranty from respected retailers. So, if it does not meet your expectations, then you can request a refund.

In reading user reviews, the chief complaint is low volume, followed by an unreal expectation of high sound quality.

The device does not have any signal gain or an amplifier, so volume is more an issue with the sound source and the ear/headphones.

Sound quality is at best, MP3 radio quality – and GIGO plays a massive part in that.

Our recommendation is these are best with amplified headphones, and if you plan to use two headphones, make sure the volume efficacy is a condition of sale.

And remember this review is applicable to the thousands of CSR8670 BT devices – none will be any better.