Here's what I know about this: iPhones haven't had an 1/8" headphone jack for some years. And there is an Apple adaptor with a DAC inside. - Are there 3rd party Lightning adaptors that work? - What is on Android phones? USB-C? - There are similar adaptors? From Samsung? 3rd parties? - What about any other phones that might come with smaller carriers, lesser known phone brands? Grazie!
Apple has an adapter that goes from lightning to 1/8" headphone connector. They were also included with the first batch of phones that came out with no headphone jack. https://www.amazon.com/Apple-Lightning-Headphone-Jack-Adapter/dp/B01LXJFMGF
The Apple lightning to headphone adapter is cheap. I wouldn't mess around with third party adapters, unless they have been tested and verified by many people as compatible: your iPhone will reject it (the phone displays a message that you have an "unauthorized device" connected to the phone, and doesn't allow the device to work). I once started a thread about iPhone lightning to headphone adapters, noting that there is a DAC inside, so in theory a third party device could improve on the DAC to produce even better sound. I tried some DAC devices, but sometimes they got rejected by the device (as an "unauthorized device"), or the device was bulky enough that I broke it in my pocket, iPhone lightning to headphone jack adapter recommendations
Apple does not want you to use use non-Apple branded headphones. And if you insist, get a share of the price you pay - thus certification requirement. With Android USB-C you generally can use any DAC/headphone amp which is natively supported in Linux. But you also can find plenty of Android phones with analog headphone connector.
I’m using a Hipdac2 with my iPhone output to IEMs. Although my iPhone supports headphones, the external DAC will fully decode MQA, higher resolution PCM and even DSD (haven’t heard it yet on my iPhone). It is a hassle to get the units configured, but the sound is worth it to me. The DAC will easily support higher-end headphones on 4.4mm balanced if you go that route. Plus the DAC has a good li ion battery, preserving battery life on your phone. It an external DAC really needed? For most people on the go, the answer is NO. Plugging IEMs directly into your phone will get the job done.
Depending what you mean, with iPhones you can't as there is no jack nor DAC, you need a DAC adaptor. If you mean upgrading the DAC may not be worth it for many people, that could be so.
I use wired headphones with my iPhone 13 often. Yes, the Apple branded Lightning to 3.5mm phone jack is small, cheap and readily available. It sounds all right though not great. I stepped up to using a Monoprice Monolith USB DAC/headphone amp. Not as expensive as one of the AudioQuest Dragronfly DACs but it works well for me. It does require the purchase of the Apple Lightning to Camera USB adaptor or the similar and larger Lightning to Camera USB3 adaptor. The down side is that you have an extended, dangling dongle and extra weight to the phone. It won't fit in your pocket very well.
Google offers a USB-C to 3.5mm analog adapter similar to the one from Apple: https://www.amazon.com/dp/B07J28BYT9?psc=1&ref=ppx_yo2ov_dt_b_product_details It's needed for the Pixel 6a.
All iphones have a dac. How else would you be able to listen to music through the tiny iphone speakers?
MAGIC! Ah, good point, but IIRC there is simply no headphone output on the Lightning connector. Hence you need the little adaptor that I think connects to the USB output and provides D/A conversion. (And in an amazingly small package, holy cow!!!)
I’m partial to these for my iPhone. Not perfect, but aesthetically and functionally more pleasing to me than the apple dongle and quite good sounding with some of my iems like the Campfire Polaris 2. I also use AirPod pros, a Cayin RU-6, and a Dragonfly Cobalt with my phone, ipad, and laptop, particularly when traveling or working away from the house. I also have a nice Sony DAP for serious listening (WM1A). Still, there are many occasions where I do like the simplicity of a simple adapter like the one linked above + wired headphones: walking, yard work, exercise, beach, etc.
The Apple adapter is a master class in miniaturization….it features both a DAC and ADC for the headset mic in their analog earbuds. While I use AirPods Pro for my day-to-day listening (mostly podcasts during work outs) I have both the Lightning and USBC version of the Apple dongle for use with my IEMs. Hard to beat for $9. Apple Lightning to Headphone Jack Adapter Teardown
Which headphones? Decent IEMs would benefit from a proper DAC dongle a lot. I'd been using the Lotoo Paw S1 but recently upgraded to the Luxury&Precision (that's a stupid name) W2, it sounds great. Both of the products support Android (USB-c) and iPhone (lightning or USB-c for Mac/Ipad). These devices are small and lightweight. My IEMs are the Campfire Audio Solaris 2020.
I can use my iPhone 10 with an Apple Lightning to Camera USB adaptor. I then connect an Audioquest Dragonfly Red DAC and plug in the 1/8th” jack from my headphones (Sennheiser 598 or Audeze LCD-X). Fine for sitting and listening to Tidal or FLAC files using an Onkyo app.
On my Android phone I use USB Audio Player Pro through a USB-C HELM Audio Bolt DAC/Amp connected to wired 'phones - sounds fantastic and plays every file format, including Tidal MQA. The HELM also works great with my iPad. Great little gadget.