iphone Headphone Output Level - Page 1
Forum section: electronics / beginners

author: joshund
author_rank: Newbie
timestamp: August 23, 2017, 08:06:12 pm
content: Does anyone know what the approximate peak to peak voltage should be when you measure the output of a digital full scale sin wave (say 1kHz) from the headphone output of an iphone (4s or newer) into a large load (1Mohm or more)? Does the signal have a DC bias or is it centered about 0V? I would measure it on my iphone but I do not currently have an oscilloscope and haven't been able to find any information about the output levels online. I'm really just trying to figure out the approximate voltage range of the output (doesn't have to be really accurate) and whether or not it has a DC bias. I appreciate your help or any input you can give me.

author: tooki
author_rank: Super Contributor
timestamp: August 25, 2017, 12:20:37 pm
content: A 1Mohm load would be a very small load. Practically open circuit as far as an audio amp is concerned. Portable audio devices are generally designed to drive loads between around 16-60 ohms or thereabouts. (Earbuds are normally around 32 ohms. This is why high-impedance headphones, like 250 ohm studio cans, won't develop much volume on portables.)Secondly, what makes you even begin to suspect that a mass-market premium product would have a DC bias? That's wasted power and fried earbuds. Modern portable devices use class-D audio amps, which really aren't gonna have a DC bias anyway. But even so, DC bias on a speaker/headphone output is a huge no-no, since it fries things. You wouldn't tolerate it on cheap devices, and since all it takes to block DC (assuming your audio amp chip doesn't do this on its own) is a capacitor, even cheap gadgets get this right. (I'm sure there must exist a chinese junk exception, but then again, those are the people making capacitive dropper USB phone chargers.)Open circuit you'll have around 1Vrms. Under real load with low-impedance earbuds, just around 0.9VrmsAnyway, Ken Rockwell characterized a number of Apple device headphone jacks, such as:iPhone 6S:http://www.kenrockwell.com/apple/iphone-6s-plus-audio-quality.htmLightning audio adapter:http://www.kenrockwell.com/apple/lightning-adapter-audio-quality.htm

author: IanMacdonald
author_rank: Frequent Contributor
timestamp: August 25, 2017, 12:37:35 pm
content: Here in the EU we have problems with phones not being able to drive anything but the supplied earbuds at even usable volume, and that is because of an EU directive limiting the max SPL, ostensibly to prevent people damaging their ears. The problem is that the signal required to reach the limit (which is set quite low of course) will not drive any quality headset or even quality earbuds, which are typically less sensitive than the screechy junk ones they supply. Result is that you either have to hack your phone or use an external amplifier. Bloody EU.What's even more frustrating is that if you plug in a set of Sennheisers they work OK for about half a second and then go very faint. Presumably it detects the presence of cans and cuts the output.Not sure if iPhones are affected, but they probably are.

author: tooki
author_rank: Super Contributor
timestamp: August 25, 2017, 11:34:30 pm
content: Quote from: IanMacdonald on August 25, 2017, 12:37:35 pmHuh? The directive, as I understand, requires a limit (defined as a certain maximum SPL as measured with the included earphones), but that that limit may be user-disabled. iPhones sold in Europe have that limit, and will show a "high volume" warning (which cannot be disabled) when exceeding it, but you can still exceed it. (In the settings, you can set it to not exceed the EU max volume, also available as a parental control IIRC).I have no trouble driving quality cans and earbuds with my iPhone, but of course I chose low-impedance models designed to work well on most devices. (Beyerdynamic MMX 300, 32 ohm; Audio-Technica ATH-M50x, 38 ohm; Etymotic ER-4XR, 45 ohm). I honestly don't know why anyone would choose 250 or 600 ohm cans for a mobile device. (I would challenge anyone who claims these $350 Etymotics and $300 Beyerdynamic are not high quality.)What device is it that turns down your cans after a second?FYI, iOS devices have a sort of limited per-device volume memory. While they obviously have no way of telling apart two different 3.5mm headphones, for example, they can identify whether it's just headphones (no mike) or a headset (headphones with mike), and remember the volume for them separately, even across reboots. Similarly, volume is remembered separately for each Bluetooth headset. And of course, the ringer and speaker volumes are remembered separately, too.

author: Circlotron
author_rank: Super Contributor
timestamp: August 26, 2017, 02:10:07 pm
content: Quote from: joshund on August 23, 2017, 08:06:12 pmMy 4S running SGenerator Lite app gives 570mV p/p from 10Hz to 17KHz. No DC offset. 1 meg load (scope input impedance).

author: Zero999
author_rank: Super Contributor
timestamp: August 26, 2017, 09:45:22 pm
content: Quote from: tooki on August 25, 2017, 11:34:30 pmI'd expect it depends on how good ones hearing is. I've no doubts on the quality of those $350 headphones. It just seems like a lot to spend on a set of earbuds. In my opinion, that sort of price is stepping into audiophool territory.

author: TheUnnamedNewbie
author_rank: Super Contributor
timestamp: August 27, 2017, 03:17:57 pm
content: Quote from: Hero999 on August 26, 2017, 09:45:22 pmIt really depends on what you are using them for in my opinion. I have somewhat expensive earbuds (200 euros) but my reasoning is that I spend more than 3 hours a day wearing them, and they last me many years, so all in all it's an investment I'm willing to make.That aside: Some headphones outputs will appear to have a DC bias on one of the pins to drive the microphone/control circuit. However, it is somewhat high output impedance, intentionally so (tens of k? iirc), such that almost no current will flow through a headphone when it's plugged in or when it has no microphone.I've also never had issues with high-impedance loads on my phone. My desk headphones are 250 Ohms, and they work just fine on my phone. They are /very/ high sensitivity tho, beaten only by my in-ear monitors.

author: tooki
author_rank: Super Contributor
timestamp: August 27, 2017, 04:47:47 pm
content: Quote from: Hero999 on August 26, 2017, 09:45:22 pmTry them out sometime before you dismiss them!In a nutshell, the Etymotic ER-4XR don't sound like earbuds. They sound like headphones. Not even a hint of tinniness. I tried a bunch of different models from various manufacturers at various price points before buying. The Ety ER-4XR was better than any of them, by a mile. It was literally "holy shit, these sound like my Beyerdynamic (headphones)!". I told the salesman "take my money before I change my mind" and haven't regretted it for a second.I will also say, the $80 Apple In-Ear Headphones (that specific name; not the regular old earbuds, nor the EarPods) get you probably 70% of the sound for a fraction of the price. But they're just not durable, I was replacing them once a year.(For context, the old Shure SE310 sounded the same and cost 4x as much.)If I'm spending $80/year on buds, I may as well spend $350 on a pair that have replaceable cords and should thus last nearly indefinitely.Audiophoolery is where you're spending on stuff and getting only imaginary improvement -- but in this case, it's a HUGE, real improvement.(As for my hearing, despite a bit of tinnitus, the last hearing test I did at my ENT doc showed no hearing loss, with my high frequency sensitivity excellent for someone my age.)

author: Zero999
author_rank: Super Contributor
timestamp: August 27, 2017, 07:58:30 pm
content: Quote from: tooki on August 27, 2017, 04:47:47 pmA lot of what you've said regarding sound quality is subjective. It's also a pretty well known fact, that if it cost you more, it will sound better to you.I'll always dismiss them because I hate earbuds. I wouldn't use them if there were given to me for nothing. I'd rather use any headphones which don't stick in my ears, but that's personal preference.

author: tooki
author_rank: Super Contributor
timestamp: August 27, 2017, 08:28:19 pm
content: Quote from: Hero999 on August 27, 2017, 07:58:30 pmWell yes, but this isn't one of those things. This is measurable: the ER4 series is hand-tuned for flat response (or in the case of the XR version, slightly boosted bass), which is verified using an actual virtual head model (each driver is measured individually, and you get the certificates with the frequency response curves in the box). Cheap buds have very nonlinear response.Again, if we were talking a small difference -- or especially a difference which cannot be measured by any scientific instrument, as is the case in audiophoolery -- then I'd agree. But this is a day-and-night difference that I think most people would readily detect, regardless of whether theylikedthe sound or not.Quote from: Hero999 on August 27, 2017, 07:58:30 pmYes it is, and you should try not to dismiss the differences in them because of that preference. I prefer the sound of cans, but I just hate using them outside the house. I think it's ridiculous to walk around with full-size over-the-ear cans on. (Smaller on-ear cans don't work for me because of piercings and above all because of the pressure against my eyeglass legs, which gets painful after a while.)

author: tooki
author_rank: Super Contributor
timestamp: August 27, 2017, 08:37:57 pm
content: Remember also that speakers (and thus also headphones and earphones) are electromechanical devices, where there are real differences from model to model. It's not like wire, which (at audio frequencies) behaves very consistently. Get the geometry of a speaker/headphone/earphone enclosure even slightly wrong and you have resonances, weird frequency response, etc. For sure, you don't need to spend $20K on a pair to get good sound. But unlike $2 vs $200 cable, where there's unlikely to be any measurable (never mind audible) difference in performance, the difference in performance between a $2 and $200 speaker/headphone/earphone will be enormous. Between $200 and $500, much smaller. It goes into quickly diminishing returns.

author: Zero999
author_rank: Super Contributor
timestamp: August 27, 2017, 10:17:51 pm
content: Quote from: tooki on August 27, 2017, 08:37:57 pmThat's true and in ear headphones should sound better in theory because there's less room for the acoustics to be a problem and making them smaller, means that any resonances should be higher up, possible in the ultrasonic range.QuoteThat's interesting. I wonder where the point beyond not being able to tell the difference is? The trouble is, it's not something which is easy to verify, because there are other factors such as brand name, aesthetics and comfort, which are all important and everyone has their own preference. For example I place comfort above everything else, hence no in ear phones, but other people will choose something else.

author: tooki
author_rank: Super Contributor
timestamp: August 27, 2017, 11:06:35 pm
content: Quote from: Hero999 on August 27, 2017, 10:17:51 pmThat could be, in theory at least. IMHO (which is just based on experience, not a scientifically valid survey), it seems that in practice, it's a lot harder to do in small buds than in big earbuds and in headphones. It'd be interesting to know what high-end earphone manufacturers, as well as hearing-aid makers, do that make theirs so much clearer than cheaper models.Quote from: Hero999 on August 27, 2017, 10:17:51 pmFor sure, the point where one can no longer notice a difference isn't the same for everyone, and you can also learn how to be a more critical listener. (Which is a blessing and a curse, I'm sure!!!)As for comfort: Again, don't write off in-ear earbuds. While it is critical to find a pair that fits you well, with the right size and shape tips, they can be extremely comfortable. I find good earbuds to be more comfortable thananyheadphones. These Etymotics, despite needing to be inserted rather deep*, are extremely comfortable for extended wear once the tips are broken in. Cheap in-ear earbuds often have very fat stems (often around 5-6mm) to which the rubber attaches, making them not very pliable, and limiting the smallest size. Expensive ones, in contrast, use extremely thin stems (around 2-3mm) that allow for far greater comfort, and more flexibility in rubber/foam tip shapes.I can't say for sure, but my hunch is that your experience with in-ear earbuds is only with very cheap ones, which are indeed rather dreadful. They have as much in common with high quality in-ear earbuds as a frozen pizza baguette has with a fresh brick-oven pizza in Naples: the name and very roughly same ingredients, and that's it.*One German review said the sound wasn't satisfactory until they were seated properly, "deep enough to tickle your nostrils from behind!"