MEASUREMENTS: Apple's Lightning to 3.5mm Headphone Adaptor [MMX62] (CES 2018 Creative Super X-Fi audio, and A/C cable "proof"?)

Ludicrous combination of iPhone 6, Lightning to 3.5mm adapter, and Sennheiser HD800 :-).

Well, as you likely already know, since the iPhone 7, Apple has removed the 3.5mm headphone port from their phone devices. Ostensibly, the rationale being that this would allow more space in the device for other goodies to enhance the feature set of the phones.

In place of the missing headphone port, Apple has included the "Lightning to 3.5mm Headphone Jack Adapter" with their phones. I've been wanting to have a look/listen to how well this little dongle thing performed for awhile but since I'm an Android guy and nobody close to me upgraded their iPhone when the 7 came our, I just remained patient. Well, over the holiday season my sister-in-law upgraded to an iPhone 8, so I finally got a hold of one of these Lightning-to-analogue out dongles to test out at my leisure :-).

As you can see, I've got my usual set-up running to measure the output from that little dongle attached to an iPad Air 2 in this image. Yes, it works, in fact this adapter should work with any iOS 10+ device.

The measurement set-up:

iPhone 6 / iPad Air 2 --> Lighting to 3.5mm jack --> 6' shielded phono-to-RCA cable --> Focusrite Forte ADC --> 6' USB --> Windows 10 laptop

For RightMark measurements, I'm using the latest 6.4.2 PRO version. Both the iPhone and iPad are on the latest iOS 11.2.2 (notice I'm using the iPhone 6 because I also want to compare the output with the headphone out on the same device). For bit-perfect playback, I'm using Onkyo HF Player latest version 2.6.0 (obviously, all EQ and resampling off) using FLAC-encoded test signals. Since I didn't find any meaningful difference between the iPhone and iPad measurements, apart from the impulse response and square wave, the rest were recorded from the iPhone for consistency.

I. Oscilloscope, Impulse Response, and Digital Filter Composite

As usual, let us start with the "microscopic" measurements looking through the oscilloscope:

Not a bad looking 1kHz square wave. Peak voltage around 1.4V (or ~1Vrms, the same as iPhone 6's headphone out). You can see the right and left channels are well balanced. Not bad for essentially an inexpensive external DAC, I've certainly measured more expensive devices with poorer results.

Headphone output impedance with a 1kHz sine wave was approximately 1-ohm. Again, pretty good, should not pose any frequency response issues even for low impedance IEM headphones.

Looking at the morphology of those square waves and the ringing, this is clearly a minimum phase digital reconstruction filter; typical for Apple for some reason (and which I do not favour). Here's the impulse response:

Should be a rather steep filter given the amount of post-ringing duration. And the "Digital Filter Composite" (based on Juergen Reis' idea in 2013) shows this:

Looks similar to what I found with the iPad Air 2 measurements awhile back. Similar enough to say that we're likely looking at the same DAC chipset inside with essentially the same filtering parameters. Without overloading the DAC by using the -4dB wideband noise, we see that it is a relatively sharp anti-imaging reconstruction filter though not exactly the most precise filter resulting in some ultrasonic "rippling" artifacts above 25kHz.

II. RightMark Measurements

Like the previous iPhone 6 as well as the iPad Air 2, it appears that Apple doesn't care for high samplerates (seriously guys, I don't think hi-res streaming is coming any time soon to Apple despite some wishful thinking since a device like this is still standard for current-generation iPhones in 2018). This little dongle does not handle anything higher than 48kHz. Here's the frequency response for a 96kHz signal as evidence:

As you can see, the signal has been resampled down.

A. 44.1kHz - 16 and 24-bit performance

First, let's start with 16-bit performance, here's the summary:

Notice that I'm compared this adapter with the iPhone 6's native headphone jack (2nd column), the PonoPlayer, the SMSL iDEA, and my main sound room DAC the good ol' TEAC UD-501.

Overall, as you can see, these days standard resolution 16/44 doesn't pose much trouble even for cellphones and a dongle like this! Most of the difference is in the tiny levels of THD and IMD. The other thing here is the PonoPlayer's unusual frequency response due to the type of digital filtering Ayre uses (minimum phase, very slow roll-off as discussed before).

Some graphs:

If we go slightly "high res", at 24-bits, we see that indeed the Apple iPhone 6 and this little Lightning "DAC" Adapter can benefit from the extra bit depth:

Alas, I typically don't bother measuring 24-bit 44kHz signals so there's really nothing good to compare this to :-). What we can say is that from a noise level perspective, the Lightning Adaptor is managing to provide up to another 3dB lower noise floor / higher dynamic range. The iPhone 6 though is capable of a better noise floor than this Lightning Adaptor.

Let's move on to 24/48 where we can compare to a few other devices in "high res" and speak more about this...

B. 24/48 performance

Summary with comparison to other devices:

As you can see, we're now comparing the Lightning Adaptor and iPhone 6 with a couple of inexpensive <$100 USB DACs on the computer. Numerically the iPhone 6's headphone jack holds up pretty well! Admittedly, I've always been a bit disappointed by the AudioQuest Dragonfly DACs I've measured (including the version 1.2 from a few years back and the recent Dragonfly Black).

We can say that the Lightning Adaptor provides approximately 16.5-bit resolution whereas the 3-year old iPhone 6's headphone output is capable of just slightly over 17-bits. For the price, so long as your device is compatible, the SMSL iDEA remains comparatively impressive from an objective quality perspective!

Graphs:

III. Jitter

So, what does jitter look like with an inexpensive Lightning DAC!?

Not the best but far from terrible! A bit of low-level noise in the noise floor of the 16-bit version which drowns out the usual square wave jitter modulation tone in the LSB.

There's some "skirting" of the primary frequency suggesting the presence of low-level timing anomaly. We also see a pair of low-level sidebands. As I've said in the past, jitter isn't really a problem these days for DACs. Remember that the audible spectrum from 20Hz-20kHz is relatively low frequency compared to the demands of megahertz and gigahertz electronics these days and great timing accuracy can be achieved without needing "femtosecond" upgrades.

Considering that this is the first time I've looked at a DAC operating off the Lightning connector, I don't see any concerns (nor did I suspect any issue). Like the ubiquitous asynchronous USB DACs that can achieve excellent temporal accuracy these days, I suspect it's the same with these little dongles.

IV. Conclusion

I know, I know... Not exactly an "audiophile" device :-). But I think it's useful to measure and have a listen even to something like this in order to obtain perspective on what the "low end" sounds like these days. Arguably this is the least expensive external DAC I have ever measured. It's "free" with current iPhones and replacement cost is around US$10 at the local BestBuy. It's also the first time I've put any Lightning port device through the test kit demonstrating yet again that jitter doesn't appear to be an audible issue although obviously that was not the nicest looking Dunn J-Test result I've ever seen. BTW, I've seen little actual information on the Lightning port, a proprietary Apple digital interface of course, said to be able to transfer data at around 25-35MB/s; about the speed of USB2.0.

So how does it sound? It's okay.

I did listen to a few tracks through the iPhone and this adaptor with my Audio-Technica ATH-M50 headphones (99dB/mW sensitivity) and it sounded decent enough. The volume was strong enough for enjoyment and frequency response was fine although subjectively I thought I could hear a bit more bass in some of the music with a stronger headphone amp... For example, recently I've been listening to Temples' Volcano (2017, DR6). A good psych-rock-alt upbeat album. Far from the best sounding recording but the iPhone + Lightning Adaptor had no problem conveying the "energy" similar to my desktop DAC (the old ASUS Essence One).

Lü Siqin's rendition of the classic Chinese piece The Butterfly Lovers Violin Concerto (1997, DR12) sounded pretty good still with the combo of Audio-Technica headphones + iPhone + Lightning Adaptor although for classical I do prefer the more "intricate" sound of open headphones (like the Sennheiser HD800, but that's of course in another price category!).

Ultimately, this little adaptor is a utilitarian device that compensated for the loss of the headphone jack starting from the iPhone 7. It basically provided the same sonic features (24-bits up to 48kHz) as the headphone output from the iPhone 6. Objectively it's actually a little noisier than the iPhone 6's jack with otherwise relatively equivalent distortion characteristics. One improvement is the output impedance is lower at around 1-ohm (as compared to about 3-ohms with the iPhone 6 at 1kHz).

I see that iFixit had a "teardown" of this adaptor awhile back. The DAC (which also has ADC built-in) remains unidentified. It looks like c't also ran some measurements but did not look at jitter and digital filtering... The bottom line is consistent with my test here; that the adaptor is slightly less resolving than the iPhone 6's jack in terms of noise performance and dynamic range.

Considering the similarity of the digital filter graph above to my previous iPad Air 2 measurements, I suspect Apple used the same basic DAC across the iPad and iPhone lines, just that in this case they attached it to the Lightning interface of course... Given Apple's history of using Wolfson/Cirrus DACs, I wouldn't be surprised that they used some variant of the WM8533 which was used a few years ago in their Lightning to 30-pin adaptor.

Ultimately, of course Apple wants recent iPhone users to buy wireless Bluetooth headphones from Beats with their W1 chip :-).

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Hmmm, nothing much new this week in the audiophile world.

I noted last week from CES 2018 that Creative's Super X-Fi headphone technology is "making waves". Looks like the AVSforum has awarded it the "Best of CES 2018". Nice. Like I said last week, it would certainly be nice to see more multichannel music be done and if it takes the support of the headphone crowd to move it forward, I'm absolutely all for that (notice on the demo in the video they're using a stereo Steely Dan track from Two Against Nature, I wonder how the multichannel DTS/DVD-A rip will sound)!

The Super X-Fi system is supposed to use a picture of one's ears to estimate the HRTF which is quite the feat (if it works as claimed) although of course getting customized measurements are always better. Internally, it processes up to 8 channels of 24/96 audio. I wonder how the multichannel data gets into it, what bitrate is being sent to the dongle device (is it lossless?) and what kind of drivers we might need to install to get it working for the typical consumer (USB to computer system?).

It has been awhile since I've had any interest in a Creative product, so I hope the Singaporeans hit this one out of the proverbial ballpark, especially at a very reasonable $150 price point if the reports are to be believed...

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Good to see that Michael Fremer made a video of a typical audio cable / power conditioner presentation at CES 2018 (skip to 18:40 for how "AudioQuest's Garth Powell Proves Cables 'Sound'"). According to Fremer's post "A.C. Cables Make A Big Sonic Difference":



If you've never heard the cable salesmen present Fear/Uncertainty/Doubt and why you need to spend extra money on cables (beyond otherwise decent wires and connectors - I'm not talking about toss-away red and white RCA connectors from Walmart DVD players of course), this is a good example of how they want you to be concerned about noise and interference. He believes there's a lot of electrical and RF noise all around us these days (could be true depending on where one lives) and modern wireless electronics like Bluetooth transmission has ruined music if you don't use "good" cables and power devices... Warning, this is time you're never going to recover in your life but I guess as audiophiles, it's part of the "price of admission" into the experiences of this hobby :-).

Anyhow, if you want to listen to "proof", start at 33:40 (yes, after 15 minutes of Adspeak). See if you agree that without AudioQuest products, the "room fell apart, bass was uncontrolled, and you know... it's like falling apart with every transient... and the top band we've just lost an octave... lost the whole definition and the whole thing is distorted and smearing because we don't have a filter we don't have the ground or its dissipation and mainly we're not giving the power supply the current it needs on demand when it needs it... we're not buffering, it needs that" (big breath here now). Sure.

The second demo was of ~1 minute of Muddy Waters from Folk Singer ("My Captain"). First, he uses a generic cable "$4-5 chord from China and it sounds like it" (gee, no bias there), then followed by their $625/m AudioQuest Thunder cable connected to the Simaudio Moon CD player (Simaudio amps and Magico speakers apparently for the rest of the system). Let's see, the AQ A/C cable is 125x the price of that China-made generic (for 1m). And that's of course the bottom of the rung for their recent "Storm" A/C cable line-up; next up that series is the Tornado for $1000/m (surely any self respecting audiophile cannot just pick the bottom tier cable!) all the way to the US$4400, 1m length, Dragon (for the most discerning audiophile of course).

Obviously YouTube is far from the best way to show an effect given the lossy compression which is bad enough but we also have camera movement, room noise, suboptimal seating, and some clipping in the original recording. I assume Fremer must believe the video is capable of demonstrating the difference... Which begs the question of why AudioQuest doesn't just release some measurements if it's that clearly audible!

For convenience, if you want to better assess the sound from the Muddy Waters demo, download the comparison files here and A/B at your leisure (I highly recommend using Foobar with ABX Tool and flipping back and forth between the 2 samples). Interestingly, the AQ cable version was slightly louder by 0.2-0.3dB; however, the peaks were clipped so it is possible that this is an underestimation and it could have been slightly higher if one were in the room. Also, I don't know if the camera/camcorder has variable gain applied to the recording.

See... Proved it, end of debates on power cables! AC cables make a "huuuuuuuuge" difference :-). Tell me what you think.

[For previous measurements, discussions and opinions on A/C cables - see here and here.]

Have a great week ahead everyone and hope you're all enjoying the music.

Addendum (January 21, 2018):
Interesting question about whether the Lightning-to-3.5mm adaptor is running 48kHz natively... No evident improvement with the 48kHz "DFC":

As for the -60dB 1kHz tone to look for obvious bitdepth truncation which typically should exacerbate odd-order distortion. I don't see it, but Lightning adaptor is much "dirtier" than just the iPhone 6's headphone out!