Apple USB-C to 3.5 mm Headphone Jack Adapter

Link to my review and measurement index thread where one can also find a full review overview, more information about myself as well as my general-ish audio and review manifesto: https://www.head-fi.org/threads/956208/

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I only give full stars. My ranking/scoring system does not necessarily follow the norm and is about as follows:

5 stars: The product is very good and received the "highly recommended" award from me.

4 stars: The product is very good and received the "recommended" award from me.

3 stars: The product is good/very good, but not outstanding/special enough to get any of my two awards. ["Thumbs Up"]

2 stars: The product is only about average or even somewhat below that and somewhat flawed/flawed in some areas. [neither "Thumbs Up" nor "Thumbs Down"]

1 star: The product is bad/severely flawed to outright bad. ["Thumbs Down"]

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Apple USB-C to Headphone Jack Adapter (A2155)


Source:

Personal unit.


Miscellaneous:

Nicely inexpensive.

Contrary to its name, the A2155 is much more than just an “adapter”, as despite its pretty tiny form factor, it houses a fairly smart sound card with a built-in DAC, ADC, automatic detection of whether anything is plugged into it, and even supports in-line remote control commands.

Rather decent unboxing experience (for the price); very nicely and cleanly designed packaging that can also be used as a carrying case (since there is no other included pouch or case other than the cardboard packaging itself).

Small.
Clean design.
White.
No Apple logo on it – the only sign that it’s made by Apple (aside from its design, but other companies have subsequently manufactured comparable-looking small DACs) is the faint grey text on the cable.

While the USB-C plug (that most likely contains all of the active electronics) and multi-purpose 3.5 mm socket appear to be well-made, the cable between them, while fairly soft and nicely flexible, doesn’t appear sturdy or durable at all but pretty fragile instead, as it is unfortunately the case with most of Apple’s cables.

Surprisingly, the A2155 supports three-button in-line remote control commands (volume up, play/pause, volume down) when used with my Windows 10 computer.

What’s definitely nice: it can be basically left plugged in all the time, as it automatically senses if anything is plugged into it and accordingly adjusts its features. If nothing is plugged in, the output is disabled automatically and it doesn’t even show up in the Windows sound menu anymore but will show up again and is selected automatically once something is plugged into it, and the setting options change accordingly to the type of plugged in headphones (e.g. with/without built-in microphone).





Sound:

My ZOTAC ZBOX CI547 nano running Windows 10 Pro 64 Bit is the only source that I’m using.

I’m only using my Apple USB-C DAC purely as a DAC for in-ears and headphones, and haven’t tested its ADC capabilities yet.

Volume Control:

Logically, the volume is controlled by Windows’ system-wide standard 100 attenuation steps (plus mute). Unfortunately, even the quietest possible volume setting above mute (≙”1”) is much too loud for me personally, so I need to further lower the volume in foobar2000 and YouTube drastically. Therefore, listening very quietly just above the audible threshold is not directly possible without any further software tweaks.

Hiss Performance:

Using my near-extremely sensitive Shure SE846, there is only the tiniest bit of barely perceptible hiss when no music is playing or when an empty audio file is played.

When used with my Ostry KC06A that are even a bit more sensitive to picking up hiss, the amount of audible hiss in quiet passages and empty audio files or when nothing is played is very little and close to being inaudible.

Using my extremely sensitive Campfire Audio Andromeda that are the most sensitive out of the three, the audible hiss is still very little, which makes the Apple USB-C DAC an amazing performer in terms of hiss performance with very and/or extremely sensitive in-ears.
As for comparisons, it even slightly surpasses my iBasso DX90, is only beat by my RME ADI-2 DAC and Leckerton Audio UHA-6S.MkII, and audibly outperforms the FiiO Q5 with attached AM1 module or my Chord Electronics Mojo.

Frequency Response (no Load):



FR unloaded

There is no real surprise here; the unloaded frequency response is just as flat as it is supposed to be.

Output Impedance (Ultimate Ears Triple.Fi 10 as Load):



FR loaded – Ultimate Ears Triple.Fi 10

Based on the frequency response deviation, the Apple DAC’s output impedance is calculated to be around only 0.3 Ohms, which is truly excellent and therefore perfectly suitable for all low impedance multi-BA in-ears.

Subjective Listening Impressions:

Neutral, clear, clean and very precise. Basically as audibly transparent, good-sounding and clean-sounding to my ears as a device could be, and therefore clearly “not broken”, which again is no real surprise but the standard for most modern audio devices.
Precise and tight bass reproduction with sensitive multi-BA in-ears.
Subjectively large (i.e. normally sized) and very accurate soundstage; slightly on the oval side.

Seriously, there’s absolutely no subjective sonic fault that I could find, and this is no real surprise either since the A2155 has shown to surpass surpass the CD Red Book standard when it comes to objectively measured audio performance.

In other words, excellent transparent performance regardless of price. There is absolutely no reason at all to pay more for a USB DAC, at least when it comes to pure sound quality with headphones.





Conclusion:

Recommended.

The Apple A2155 USB-C to Headphone Jack Adapter is, despite its very low and extremely competitive price, packed with many features, surpasses CD Red Book standards, has got an excellently low output impedance, comes extremely close to being ideally hiss-free with the most sensitive in-ears (wherefore it is just a shy bit below absolute perfection/“Highly Recommended” but still surpasses even many of the better devices in this regard; in addition, unfortunately the lowest possible volume setting (in Windows 10) is too loud for me personally (without further reducing the software gain in the music player interface)) and sounds audibly transparent.

Aside from some people probably wishing for “more power” for their respective listening levels with the headphones they use, and probably for more features (such as dedicated volume control buttons or more inputs and outputs), just based alone on pure sound quality or a more luxurious appearance and/or better build quality (the cable could indeed appear more durable), there is absolutely no reason to pay any more for a DAC.


Photos:

This is odd coming from apple to have one of the cheapest and best sounding usb c to 3.5mm adapters on the market. It is significantly better than some phones with crappy 3.5mm output quality. This is an easy way to give your phone or your computer a good improvement in sound. It works flawlessly on my phone and computer. Durability remains to be seen but so far I am happy with the sound. Hearing no obvious flaws, I am only using this to drive my low impedance headphones like my grados, ksc75 and westone iems. Some 3.5mm ports on phones that I have plugged my IEMs into make a pop sound but not for this adapter which is good.

A must try for anyone curious about usb c to 3.5mm audio.

The 2018 iPad Pro lost the headphone jack but gained a USB-C port. Apple thinks that these new iPads ought to be used with Bluetooth headphones, so they sent Airpods to the bigger tech sites and YouTube channels along with the review units. Like it or not, wireless headphones are the future. But are still times when you want to use wired headphones. For example, if you want to use the iPad as an electronic musical instrument, you’ll want to use a wired connection for its low latency. Bluetooth headphones are tens, if not hundreds of milliseconds slower, and it makes the instrument feel a lot less responsive, even unplayable. I’m no gamer, but I imagine that some games could need the same kind of snappy response. For these kinds of applications, Apple now sells a USB-C to headphone jack adapter.

I’ll leave it to others to describe how well this dongle works with the new iPads. Macs don’t need it yet because they still have the headphone jack. A quick online search shows that some folks got this adapter to work with Android phones like the Google Pixel 2. I wanted to see how well it would work with Windows 10 PCs because so many of them have terrible built-in audio.

So far, I have tested the Apple USB-C adapter on a 2016 Lenovo Thinkpad Carbon X1 (running Windows 10 April 2018 update) and a Microsoft Surface Go (October 2018 update). I’m happy to report that the adapter just works. Windows won’t show it in its list of devices until you plug something in the 3.5mm jack. Here are the sample rates and bit depths that are supported:


I made some basic audio measurements just to make sure my units weren’t malfunctioning. TL;DR version: they’re probably working just fine. I’d like to see others make more careful measurements that go beyond just verifying that it works, like I did.



It sounds like?
As expected, the audio performance of this adapter in Windows is similar to that of iOS devices. I tried it with all sorts of headphones and IEMs, and I compared the USB-C dongle with the Lightning headphone jack adapter and also the last iPhones and iPads that still had the headphone jack. I’m pretty much getting the iPhone and iPad sound out of a Windows PC.

There isn’t any obvious distortion or noise. The only exception is on a Logitech UE600vi, where I can hear a very faint background hiss during quiet tracks. When I’m playing the digital zero wav file, the noise doesn’t change its character when I make the SSD busy or move open windows around. When it was released, the iPhone 6S had a problem with strange electronic noises that you could hear on sensitive IEMs when going to the task switcher screen and switching apps. That doesn’t happen with this USB-C adapter. (BTW, it’s not so bad anymore on the 6S since iOS 11. The noise still changes, but it’s quieter and less offensive.)


The Apple USB-C headphone jack adapter gets the same 1 Vrms maximum output as other iOS devices. (Assuming that your country isn’t limiting the volume.) It should be well established by now how loud it can get. On pop tunes like the one in the video pictured above, a satisfying volume level for me with the HD600 is 58 (out of a maximum of 100 in Windows). The HD600 is a walk in the park for this adapter because it draws so little current even at maximum volume. When level matched, it sounds about the same as a competent dedicated headphone amp. That is, if you can get it level matched. Some kinds of music are so quiet that you might not be able to get the HD600 loud enough on the dongle.

The UE600vi, on the other extreme, has a 9-ohm DC resistance. If you crank up the volume, the distortion will be a lot higher than on the HD600. Fortunately, you won’t be doing this on low-impedance IEMs because they’re usually very sensitive. The UE600vi, for example, has higher than average sensitivity, even among balanced armature IEMs. When I was watching movie trailers on YouTube, I had the volume level anywhere between 8 to 12 in Windows.


Comparison with the Google Headphone Adapter


Last year, Google removed the headphone jack from their Pixel 2 phones. Their accessory USB-C audio adapter was $20 at launch, but they lowered the price to $9 to match Apple’s Lightning adapter after strong criticism from Pixel fans. I can see why Google’s adapter was more expensive at the start. It has extra abilities, like 1.88 Vrms output—5.5 dB higher than either Apple adapter. And it manages this without any special cables. The Google adapter can also change its operating mode to 400 mV maximum when it detects a lower-impedance load like an IEM.

I ordered three Google adapters last year and tested one of them. I wrote about it in this thread: link. They’re quite competent, so it’s a shame that Google discontinued them. The new model is more expensive at $12, and reports online show that its performance is much worse than the original’s.

Apple’s and Google’s USB-C audio adapters sound similar. I don’t detect any obvious distortion or noise from either one, except for the noise on the UE600vi that I mentioned before. The character and the level of their noise is very similar, even down to the measurements. Both adapters’ output impedances are similarly low as well, so they deliver a flat response to almost all headphones. On my headphones and IEMs, they sound about the same.

The adapter also sounds like the headphone jacks on my Macs. Windows PCs, on the other hand, usually have worse onboard audio. My Thinkpad, for example, has noisy output. The Surface Go is quiet, but part of that is because of its high output impedance; I measured 46 ohms. An easy load like an HD6xx sounds ok, but it’s a disaster for some balanced-armature IEMs with multiple drivers.

Last year, I got the Google adapter to work on the Nexus 7 tablet and the 2017 Amazon Fire HD 10 using an OTG cable. Those two also have weak headphone amps with high output impedance. I have yet to test them with the Apple adapter. I’ll update this report when I do.

UPDATE: November 16


The mic input is good for hobbyists who want to make measurements
Windows 10 recognizes the Apple USB-C audio adapter’s microphone input, so any microphone that works with an iPhone should also work with Windows. The Dayton Audio iMM-6 measurement mic, for example, works just fine. A few hobbyists have used the iMM-6 or Chinese IEC711-compliant clones to measure the frequency response of their IEMs. Apple’s USB-C adapter works well with these. It doesn’t have the bass roll-off of the Google adapter. It’s also much cheaper and more portable than the Startech ICUSBAUDIO2D audio interface, while having a lower output impedance.


Even if the Google adapter rolls off the bass, it's something electrical that can be handled by a calibration curve, unlike the coupler's acoustic transfer impedance, where one calibration curve cannot fit all. The Apple adapter makes it one less thing to worry about.


What we have so far
$9 gets your Windows PC sound that’s good enough for all but the most difficult headphones and the most persnickety audiophiles. It’s also very light and portable. So what’s not to like? Maybe its build quality. Apple’s Lightning audio adapter has a bad reputation for being too fragile and easily damaged. It remains to be seen if this USB-C adapter will be the same. It has a similar construction.

It's a good thing, then, that it's cheap and easy to find in stores. Apple stores obviously have it in stock, but I suspect that Best Buy, Walmart, and Target will have it on their shelves soon. It’ll be strangely ironic if Apple’s USB-C dongle becomes the most common headphone adapter for Android phones. Maybe then, Android users will join their iPhone-using brethren in leaving one-star reviews online if this thing really is fragile. Courage!