Apple Lightning Adapter Audio Quality

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iPhone 7 Plus and A1749 adapter

Apple A1749 Lightning Audio Adapter on an iPhone 7 Plus in its saddle brown case. I'd get the iPhone 7 Plus at Amazon or at this link directly to them at eBay (see How to Win at eBay). bigger.

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iPhone 7 Plus and A1749 adapter

Apple A1749 Lightning Audio Adapter, about $9. bigger.


January 2017   audio reviews   Apple   headphones   tube amps   all reviews



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The iPhone 7 Plus and iPhone 7 have no headphone jack, but it includes — free — this model A1749 audio adapter that provides a 3.5mm analog line-level or headphone audio output from the phone's lightning connector. It provides a 3.5mm jack for your headphones or a jack to plug a cable into a conventional Hi-Fi.

You can just leave this attached to any set of your favorite headphones or Hi-Fi cables; extras sell for only $9 each. Go crazy.

It's only 3" (75mm) long and only weighs 0.085 oz. (2.4g). If you look under a microscope, it's actually marked "Model A1749" in white on white on the 1" (3cm) piece of flexible cable.

Apple knows what they're doing. This tiny adapter houses a microscopic stereo digital-to-analog converter (DAC), a stereo headphone amplifier, a microphone preamplifier and monophonic analog-to-digital converter (ADC) and power converters to run this all.

It's smart enough to respond to remote control commands and has circuitry to let it tell the phone what, or if, something is plugged in. For instance, it's so smart that it remembers different volume settings for my pro headphones that only have three terminals on their plugs versus my mobile headphones that have 4-terminal (TRRS) connectors with remote & mics. Yes, your remote control and microphone in your headphones will work exactly as they have on old iPhones.

All this circuitry is hidden inside an adapter smaller than most passive adapters, and as you'll see, this invisible circuitry outperforms most external DACs and headphone amplifiers. Pretty impressive, but you have to realize that Apple has a lot more smart people and the world's nest audio engineers that "audiophile" companies can't afford. Heck, most of today's audiophile and mainstream audio companies can't even afford the laboratory facilities I have. Apple has the resources to make this crazy little adapter state-of-the-art. It's essentially the same circuitry that used to be inside the phone.

You need iOS 10 for the adapter to work on older devices. iOS 9 and before predate the headphone-jack-less iPhones, but if you have iOS 10 it works great on my old iPhone 5S — not that you'd need it to.

If you use this adapter with a device that has a headphone jack, you can only use one at a time.

No, you can't charge your phone while you're listening to headphones or the audio output in your Hi-Fi, but so what: you don't want to be plugged into the wall when you're trying to enjoy headphones, and running from battery power ensures you won't have any hum from ground loops with your home Hi-Fi — again far better than using an external plug-in-the-wall DAC.

If you want the best quality for playback from iOS which also frees your iOS device from any cords, I use AirPlay to stream losslessly into an Airport Express and use the AirPort Express' analog output. I can plug the AirPort Express into my Benchmark DAC1 HDR, but I don't hear any difference.



These are measurements of the 3.5mm analog audio output of my A1749 adapter plugged into my iPhone 7 Plus playing signals in its Music app.

Quite simply this microscopic adapter has the same superb audio quality of all my other iOS devices. It's actually better than earlier iOS devices like the year-older iPad Pro and iPhone 6 Plus.

Here are some quick measurements of my iPhone 7 Plus made in my laboratory with a state-of-the-art Rohde & Schwarz UPL audio analyzer.


Output Source Impedance

Output source impedance measures 1Ω at 1,000 Hz, which is very low. That's good!

Higher output source impedances lead to frequency response imbalances caused by the varying real impedance of actual headphones with frequency, and also leads to low-frequency distortion when driving real headphones.

The ultra-low output source impedance of the A1749 lightning audio adapter included with the iPhone 7 Plus is so low as to stop any of these potential problems.


Frequency Response

Apple iPhone 7 Plus Audio Measurements

iPhone 7 Plus and Lightning Audio Adapter driving a 37.5Ω load. It's the same at 200kΩ.

It's flatter than most audio analyzers.

I measure -0.075 dB at 18,500 Hz, -0.15 dB at 19,250 Hz, -3.5 dB at 20,900 Hz and then it cuts off sharply to -95 at 21,700 Hz.

This is flawless; bravo!


Harmonic Distortion Driving 200kΩ

Driving 200kΩ is what we see when driving the line input of a Hi-Fi system:

Apple iPhone 7 Plus Audio Measurements

0.0011% THD and harmonic distortion components at 1 kHz at 0 dBFS into 200KΩ at maximum output level.

The harmonic distortion is mostly second-order. Bravo!

This is vanishingly low, lower than most analyzers can measure. It's the same as the iPhone 6S Plus and twice as good as the iPhone 6 Plus and iPad Pro.


Harmonic Distortion Driving 300 Ω

300 Ω is what we see typically when driving high impedance headphones. The 300 Ω resistive load I'm using is a much easier thing to drive than real headphones.

Apple iPhone 7 Plus Audio Measurements

0.0011% THD and harmonic distortion components at 1 kHz at 0 dBFS into 300Ω at maximum output level.

The THD driving 300 Ω is even a little lower than into 200kΩ and harmonic distortion again is mostly second-order. Bravo!


Harmonic Distortion Driving 37.5Ω

37.5 Ω is typical for most mobile headphones. This is driving a resistor, which is easier to drive than real headphones, but I was too lazy to hook up real headphones in my lab for this test.

Apple iPhone 7 Plus Audio Measurements

0.0035% THD and harmonic distortion components at 1 kHz at 0 dBFS driving 37.5Ω at maximum volume setting.

This is extremely low; better than most high-priced external mobile DACs!


© Ken Rockwell. All rights reserved. Tous droits réservés. Alle Rechte vorbehalten.


Analysis & Recommendations

This tiny Apple device has better performance and more and cleaner output than many fancier "audiophile" devices I've tested. Apple has more resources to make better stuff than the smaller companies. Most 3rd-party headphone amps and DACs, all be they bigger and far more expensive, put out less clean power into 32Ω loads, and do it with more distortion, poorer sound and lousier frequency response.

If you're using regular headphones (under 100Ω), you can't do better than using this adapter or just plugging it into your iPhone, iPad or iPod. Only if you're running 240Ω or higher headphones are you likely to need a professional amp like the Benchmark DAC1 HDR to get more output.

Apple has more smart people and more resources than any other audio company on the planet, so as we see when it comes to audio engineering, the iPhone easily outdoes many so-called "audiophile" products. Most of the mobile DACs and amps I test poop out and can't drive 32Ω loads as cleanly or as strongly.

For enjoying music, you will probably get poorer performance if you waste your time and money with outboard DACs or headphone amplifiers; the iPhone and this adapter already has the best there is.

Why do commercial audio magazines tout external DACs and amplifiers? Because that what their advertisers are trying to sell!

The only reason to get an outboard headphone amplifier for use with your iPhone 7 Plus is if you have high-impedance (100Ω or greater) headphones like the 600 Ω beyerdynamic DT880 which often require more voltage than the 1V RMS maximum from iOS devices and this adapter. In this case, you still don't need a DAC; the analog output from this adapter will probably be better than what you'd get from an expensive outboard DAC!


© Ken Rockwell. All rights reserved. Tous droits réservés. Alle Rechte vorbehalten.


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30 January 2017