Combination headphone amplifiers and DACs come in all sizes. We’ve seen lots of compact ones over the years, but the ALO Audio Pilot DAC is the smallest we’ve seen outside the analogue audio adaptor that used to come with iPhones. But it is way more capable than the iPhone dongle.
- Super compact
- USB Type-C for computer/Android phone connection, with Lightning adaptor included
- Carry pouch included
- High resolution audio out to 384kHz and DSD128
- Low – 1.2 ohms – output impedance
- 14mW/+11dB into 300-ohm loads; 50mW/+17dB into 16-ohm loads
- Very low noise, up to -118.9dBA
- The ALO Audio Pilot drove my IEMs and on-ear headphones to high levels, with clean authoritative sound. It seems almost ridiculous to get such big sound out of something that looks like a bit of wire with a swelling on each end.
- Price: $219
- Available here
What is the ALO Audio Pilot?
Well, it’s a super portable digital to analogue converter and headphone amplifier. Chances are your phone doesn’t have an analogue headphone output, and even if it does its audio quality is probably iffy. Likewise, with many computers.
Now, in what follows, I’ll mostly be using a computer for listening and testing, but clearly ALO Audio designed the Pilot with phones in the forefront of their minds, given how small it is, and given that it’s fitted with a USB Type-C plug and is packed with a small adaptor for the Lightning ports on iPhones.
The whole thing is barely 110mm long, and most of that is a flexible cable between the USB plug and the in-line 3.5mm socket. It weighs just 4.7 grams, or 6.8- grams if you include the small USB-C to Lightning adaptor plug.
It comes with a nice soft mesh bag with a draw string. That’s big enough to hold most in-ear earphones as well.
High end DAC
Somehow they’ve squeezed into that small space an ESS Sabre ES9281C PRO DAC/headphone amplifier. This is the top of the range of super-portable DAC chips announced (originally as the ES9281 – I think the C-suffix might be related to the USB Type-C connection) by ESS. It’s rated to support PCM at up to 32 bits and 384kHz sampling and Direct Stream Digital in standard and double-speed (DSD128) formats. And as top of the line, it also supports MQA – Master Quality Audio – a Meridian-developed technology which provides for authentication of the audio stream, optimisation for (certain) DACs, and the folding of high-resolution audio into standard resolution audio streams.
That’s way more than the capabilities of an iPhone dongle, which is locked to 48kHz decoding.
The output is rated at two volts RMS – the same as a CD deck, for example – a signal to noise ratio at 120dB and THD+Noise of 0.0006%. Oh, and the output impedance at less than two ohms.
Um, no. I plugged the ALO Audio Pilot into my Android phone, plugged a set of old Apple ear-busting buds into it, and called my iPhone. The inline microphone on the buds cable didn’t work, nor could I hear the call through the earphones. I switched and called the Android from the iPhone. Same thing.
(I checked, of course, with analogue dongles for the iPhone and Android phone, and they both worked properly with the earphones.)
So, no, the ALO Audio Pilot is not for handsfree calling like, say, Bluetooth earphones.
The ALO Audio Pilot is simply for listening to audio playing software, including streaming apps and podcast players. The TIDAL app on the phone did not invoke the MQA processing in the unit.
Listening with the ALO Audio Pilot
I used three sets of eargear for listening to music using the ALO Audio Pilot DAC: the not-yet out Sennheiser IE 300 in-ear monitors (you’ll see them in March), the older, more expensive Final Audio B3 in-ear monitors, and the full-sized (and now, sadly, superseded) Focal Elear over-ear headphones. The last was to see how it would go with something with some heft.
The sound I heard was of a character entirely determined by the earphones or headphones. Which is a good thing. The ALO Audio Pilot did its job, decoding, amplifying and driving the headgear without doing anything to alter the sound. (“Alter the sound” is a synonym for “damaging the sound”).
The Sennheiser IE 300 earphones have a nominal 16-ohm impedance, and a sensitivity of (by my calculation) 106dB/mW. The low impedance is towards the bottom of the usual range for earphones, while the sensitivity is fairly high. I have them fitted with the memory foam tips for an excellent ear seal. They produced a solid and deep bass, and extended top end and their own characteristic lower treble bump. They sounded essentially identical to when they’re plugged into the iFi ZEN CAN, which is a headphone source I simply love. The ALO Audio Pilot easily drove to whatever volume I was prepared to endure. At the moment I’m listening to Roxy Music’s “Sea Breezes” from the band’s debut album from TIDAL (this isn’t MQA encoded) at comfortably loud level, and the volume control is at about one third. The bass line is full and easily followed, the unusual drumming which kicks in about halfway through is a touch too full of treble, courtesy of these earphones, while the clarity is superb.
Switching over to the Final Audio B3 – they’re very slightly higher in impedance, very slightly lower in sensitivity – opened up the sound considerably. They also have a somewhat prominent upper end – they revealed the hiss on the gorgeous track “Nobody” on Ry Cooder’s 1978 album Jazz – but they present that recording in a tangible, right-there-with-you sense.
The 40mm drivers in the Focal Elear headphones are made of a lightweight aluminium/magnesium alloy, but they are inevitably heavier and hard to move than the 7mm dynamic drivers in the Sennheiser earphones, and the balanced armature drivers of the Final Audio B3s, and they are much higher in impedance at 80 ohms, but the ALO Audio Pilot had no problems in controlling them very nicely. That Ry Cooder track had a very natural balance, while retaining the openness of the Final Audio earphones.
Indeed, I spent far too much time simply enjoying music with the ALO/Focal combo. With that Rush album I mentioned earlier, the bass was strong. As I bounced around my TIDAL “Collection”, I found the drums and bass on the Janis Joplin track “Kozmic Blues” (excuse the spelling, it was the 60s) were compelling and realistic.
The point of all this? The ALO Audio Pilot drove these three sets of quality in/on-ear units to perform to pretty much the best of their abilities.
There’s a single indicator LED. It glows blue for 44.1kHz and 48kHz PCM signals and red for higher resolutions. Plus magenta if its receiving an MQA signal.
When I started up TIDAL, it recognised that the ALO Audio Pilot was MQA-enabled and asked if I wanted it to be the output device. Yes, of course I did. TIDAL then announced that “This MQA device is now active and set to Exclusive Mode.” I started the Rush album Permanent Waves playing, because I know that album is unfolded to 192kHz sampling by my regular MQA DAC. Sure enough, the magenta light lit on the ALO Audio Pilot when I started it playing. But when I checked the settings, I found that “Passthrough MQA” was switched off. That meant that the TIDAL software was unpacking the high-resolution audio, not the DAC. I switched it on and the indicator light flicked over to blue, which meant standard resolution.
Hmmm. What can this mean? I think it means that while the ALO Audio Pilot is MQA-compatible, it cannot unpack the higher resolutions, so TIDAL has to do that. To confirm, I sent some MQA-encoded music to the DAC using JRiver. With my regular MQA-enabled DAC, this stuff unfold to 352.8kHz sampling. The indicator light remained firmly blue. It did not recognise the MQA encoding.
I recorded a snippet of music from output of the ALO Audio Pilot, streamed from TIDAL, with “Passthrough MQA” off and on. With it off and the light glowing magenta, the was signal (musical or not, I don’t know) out to beyond 28kHz:
With it on and the light showing blue, the output stopped dead at 20kHz
Measuring the ALO Audio Pilot
If you’re thinking of using the ALO Audio Pilot to feed a hifi system, expect an output similar to that of a CD player: two volts RMS. With a 300-ohm load, equivalent to a fairly high-impedance set of headphones, the output was just under 14mW. I like to express those power outputs in decibels with reference to 1mW. That way you can just add the figure to the sensitivity rating of your headphones to see the maximum level to which the headphone amp can drive them. In this case, that’s a little over 11dB. So, if the 300-ohm headphones were rated at 102dB/mW, the ALO Audio Pilot could drive them to a maximum of something like 113dB.
Into a 16-ohm load, the device delivered 50mW, or 17dB above headphone sensitivity.
The output impedance of the unit was around 1.2 ohms, which is a quite good rating. It should not alter the frequency balance of headphones in any discernible way.
Measured total harmonic distortion was 0.00055% unloaded, and even driven at 0.5 volts RMS into a 16-ohm load (that would be loud), it rose to only 0.0012%. Effectively perfect.
Noise and frequency response
Connected to my Surface Pro 2017 while it was disconnected from everything, noise was at an extremely impressive -118.9dBA. With the SP2017 plugged into its dock, which was in turn plugged into both Ethernet and power, the noise was at -103.4dBA. So the unit isn’t very good at isolating its output from noise received via its USB connection. Still, that noise level was still below the noise inherent in CD-standard sound, so it was still absolutely inaudible. Here are the graphs:
That was, of course, with 24-bit audio. With 16-bit CD-standard audio, the noise was at -97.7dBA. Which is as good as it gets with 16-bit audio:
Of course I checked out the frequency response. With 44.1kHz signals, the low pass filter kicked in hard, and a bit early at 18kHz. That was surprising.
A mysteriously variable frequency response
Even more surprising was that with high resolution (192kHz) audio, the shape of the frequency response was different depending on which computer I used. Significantly different. When plugged into the Surface Pro 2017, it had the traditional slowish roll off, down by 1dB at 55kHz and 2dB at 77kHz. But when plugged into my ASUS ZenBook, the level stayed dead even to 77kHz before hitting a brick wall filter.
Different computers, but the same software. The only physical difference was that I used a USB Type-C to USB Type-A converter so that I could plug it into the Surface Pro. I don’t see how that could make such a significant difference.
Here’s my hypothesis. Many of the high-end ESS DAC chips offer several choices of filter. They have names like “Fast Rolloff”, “Brickwall”, “Minimum Phase Slow”. I suspect that somehow the ALO Audio Pilot had the “Brickwall” filter triggered when it was plugged into the ASUS computer, and the “Fast Rolloff” filter when plugged into the Surface Pro. Why and how, I don’t know.
The only real drawback of the ALO Audio Pilot is that it doesn’t support phone calls. Which is a little odd, considering that it seems to be aimed more at phones than computers. Still, if someone rings, just pull off the headgear and use the phone in the usual way.
So, if you want an extremely high-performance, highly portable DAC for your notebook computer, Android Tablet or iPad, or indeed your phone, check out the ALO Audio Pilot. Bring your preferred travel earphones or headphones into a store, and have a listen.