Disclaimer: I purchased the adapter in this article direct from Apple. It is a steal.
UPDATE: Unless I read, re-read, and edit them 20x, my articles come away reading like grammatical mush. I hope I've corrected the most egregious of them. Further, I have added an sentence explaining what I mean by 'the main limiting factor' to the second paragraph and re-written the intro to the first. Originally, the final paragraph read like a grade one essay. After brushing it up, I hope I've taken it to middle school.
Several articles about Apple’s Lightning to 3,5mm Headphone Jack Adapter are tickling the audiophile internet. These include: Heis’s appraisal of it attached to volume-capped European phones, Larry Ho’s Facebook thread (thank you Marcus) , which lambasts its jitter rate, Inner Fidelity questioning whether or not it utilises an onboard ADC to convert the signal to analogue before amplifying it in-house for the headphones, among others.
Heis’s results are somewhat of a sham. Volume is the main limiting factor in determining signal to noise ratios, channel fidelity, etc. You can't have a signal-to-noise ratio of 108dB if your signal maxes out at 99dB. Ditto any other benchmark. Necessarily, volume-capped iPhones induce results which misrepresent the hardware. Not that 99,6dB DR is anything to scoff at. But as even my amateur RMAA results (below) show, the real numbers are far better.
Larry Ho’s observations, however, are astute. Vis-a-vis an iPhone 6, the Lightning adapter’s jitter results could be problematic, at least on paper. While neither his, nor my setups are professionally calibrated for the testing of audio gear, our results describe a similar outcome. Through the adapter, jitter is evident at higher rates between 1kHz-delineated poles than through an iPhone 6’s naked headphone jack. Of course, the role of jitter outside the audio bench is hotly debated. And it’s not a discussion into which I wish to dive.
Jitter, or something similar, may be culpable in the differences I hear between the naked iPhone 6 jack and the iPhone 6 penetrated by the Lightning adapter. They are: sometimes hot and distended chimes and lower-voiced percussion, which are particularly audible in my favourite weekly radio show: A State of Trance. I say may because: 1. the culprit could be something else all together; 2. my brain may be playing tricks on me.
Placebo or no, I am otherwise impressed. The adapter’s noise floor is at least as low as the iPhone 6’s, and its ability to drive low-impedance earphones and headphones, and to sustain high volumes with a minimum of IMD artefacts, are noteworthy. In fact, under load, its low THD and IMD numbers power past many high-end DAPs. And all of the above occur whilst maintaining better overall stereo separation than a naked iPhone 6.
Sure, the Lightning adapter shows higher base levels of between-pole jitter. But it is a 9$ USD adapter. That's two Starbucks. That's 100s of liquorice jelly beans. Many DAPs costing hundreds, if not thousands of dollars, show jitter which peaks as high as -50dB. The iPhone 6 shows higher distortion peaks for a greater portion of the THD test.
Jitter may matter. And if so, have a go at this 9$ aftermarket cable. Apple have done away with yet another familiar interface. At times, this remove-it-when-possible design ethos is infuriating. In this instance, however, Apple have with one hand given (a great, cheap adapter) and taken away (the familiar 3,5mm port). I'd rather have a go at pricey, dedicated DAPs whose performance driving earphones only barely nudges out this adapter, or which pales in comparison.
Below are zoomed unloaded THD results for the iPhone 6 and the Lightning to 3,5mm Headphone Adapter:
Below are zoomed loaded THD results for the iPhone 6. Load: Earsonics SM2.
Below are zoomed loaded THD results for the Lightning to 3,5mm Headphone Adapter. Load: Earsonics SM2.