Just because Apple decided that nobody needs a 3.5mm jack on what has become people's primary music device (and all of its competitors followed) doesn't make it true. If you have wired headphones, earbuds, or IEMs (in-ear monitors), you'll need an adapter. The thing is, phones output digitally now and when companies removed the headphone jack, they bypassed the DAC that the silicon typically provides. That means this is a more complicated adapter, as it needs to have its own DAC (digital to analog converter) embedded in there.
Apple started the problem, and it offered a solution: a $9 dongle that converts from Lightning to 3.5mm. That makes it one of Apple's least expensive products of all time, but does it sound any good, and how much do you need to spend to get something noticeably better? (Spoiler: the Apple adapter is actually a bargain for what it is, but if you have good headphones you absolutely can do better.)
A while back, ifi audio sent me their $329 GO bar, which is a great little DAC/headphone amp combo that has a plethora of features, but the one that caught my eye is a special mode to deal with sensitive IEMs. It sounds great, and I will happily recommend it in its category, but if all you're trying to do is connect wired headphones to your phone, it's crazy overkill. So when ifi audio announced a much simpler product, the GO link, for just $59, I had to get one in. The GO link absolutely nails the assignment of adding a good DAC to anything without a 3.5mm headphone jack at a price that makes it an impulse buy. It natively supports USB-C and ifi Audio includes little attachments for Lightning and USB-A (to use as a better DAC than the one in your PC). Unlike the GO bar, it lacks a case, but most people will leave it attached to their headphone cable so that's fine. And it isn't so simple that you can't use made up words to talk about it with your audiophile friends, according to the website, the GO link features a, "Discrete ESS Sabre Hyperstream DAC chipset with time domain jitter eliminator, discrete oscillator and 112dB dynamic range for discerning listeners."
I started my discerning listening with the iPhone 14 Pro and Drop HIFIMAN HE-X4 headphones (budget planar magnetic headphones that deserve their own review someday). The difference between Apple's dongle and the GO link was easy to hear: on the GO link, instruments had more separation and the noise floor was slightly lower. I found it easier to discern certain elements (a unique time signature on the drums, instrument tambre), and the music was more engaging overall. For $9, it's hard to complain about Apple's dongle. It's not bad! But if you are an active listener and have invested in high quality headphones, there is easily a significant enough difference to justify the expense of the GO link.
Next, I tested the ifi Audio GO link on a [embargoed upcoming Android phone] and compared it to Anker's $20 USB-C to 3.5mm dongle. On the relatively inefficient HIFIMAN headphones, the difference was stark: the GO link can play so much louder than the Anker that it isn't fair -- the Ankers are a poor fit for this application. Apple and Anker do not specify output power on their adapters, but ifi Audio marketing does: "power output of 70mW into 32 ohms, and a maximum voltage output of 2.05V into 600 ohms."
ifi Audio also claims that its S-Balanced circuit delivers better performance on IEMs, too, so I tested them with Ultimate Ear UE12 IEMs. These require minimum power to drive, so the Anker was much more competitive. The GO links still played louder, but on IEMs that's irrelevant unless you want to damage your hearing. At more reasonable volume levels, the GO link did sound a bit better than the Ankers -- I noticed that bass drum kicks were a bit fuller -- but it's subtle. Whatever DAC Anker is using does sound good and they are a third the price.
Overall, given the simplicity and versatility with both input (USB-C, USB-A, Lightning) and output (even on more demanding headphones) the ifi audio GO link is a no-brainer. Highly recommended.