Fosi Audio DS2 USB C to AUX Headphone Amp DAC Dongle 3.5mm Jack Audio Portable Amplifier Dual Output DSD256 4.4mm Balanced High Resolution CS43131 for iPhone 15 Pro Max Plus iPad Android Phone

---Update---Fosi has been communicating with me and been very helpful to solve this issue. They are so nice to deal with and glad to have your business and I'm glad to give them mine. They must have the smartest tech support too to be able get through to me the things they have been able to when I've asked them for help. And they have a lot of very great electronics that most of us can't get enough of! :)---Original---I bought a new item and label on box says new too but the round tape that was trying to seal it closed(see picture) was barely left with any adhesive left in it and full of lint as if it had already been opened and tried to be resealed and returned for resale or to be refurbished so I opened it and while opening it it made so much noise from everything loose inside. But I did not buy a used or refurbished item that this appears to be, nothing inside was in place. I figured as long as I had it I might as well give it a listen, so I did. I have many Sabre DAC chip equipped pieces whether in phones or dedicated DAC/amps and most recently a dongle from HiBy, an FC4 and I thought this would be a nice change getting away from ESS chips and give Cirrus chips a go, I couldn't be more surprised when A/B testing them(from memory((from side by side))) that are so very similar. I don't possess the words to describe how minimal the differences there are between the 2 chips are when used in these 2 applications, it is really amazing. I was expecting a lighter, relaxed, atmospheric, type of performance from the DS2 but it is every bit as analytical as the HiBy and Sabre chips. Still worth having both to me by the way, due to power gains had in the Fosi DS2. You wouldn't guess there were gains in power made in by the DS2 until it's about half way turned up then it's just thick and loud sound. Beautiful, thick and loud. I don't quite know how adjustability is done on the DS2, I think instructions suggest downloading the HiBy music player app which in all fairness has very many types of adjustments DACs it's just that the player itself seems to be causing a lit of problems for me, so I'd use it for adjustments and go back to your normal player for your music and and streamer once done with adjustments. That's just what I've found to be best for adjustability on HiBy and may not be true of Fosi. Oh also, the HiBy player tries to load twice when I plug in my USB dongle, so I uninstall the player until I want adjustments. Crazy but true. LolAnyway, I can't say enough good things about this Fosi DS2, I wish it shipped looking like it was actually new and left me not questioning, but it sure seems like a high performance, very high quality, very great value. Performing equal to many above it's weight class and caliber. I'm so surprised it sounds nearly identical to the Sabre DAC chips that I'm used to, I've read so much about Cirrus and thought I knew what I was getting into. I pleased with the sound and will keep the DS2 as part of my setup due it's power alone and clean power at that. And Fosi is now a part of my future equipment too! This really impressed me.I hope I've been helpful,Thank you.

Easy to use, using it to drive a pair of iems for my PC. Definitely more powerful than I needed but works great. Definitely helps make the audio quality better, and louder. No noticeable heat using it on the PC at all. Size is ideal for being mobile or just tossing it on your desk and not taking up a bunch of desk real estate which can be a big deal depending on your desk size. Haven't really used the volume controls too much since I can just do it directly on the computer but they are functional with windows 11. Overall of if you're on the fence about purchasing this, it will serve you well especially at this price point!

I've used this little Fosi DAC/Amp at the gym daily 5-6 days a week for 2 hours a day for weeks.Below is a quick pro/con summary and the associated gear I used with the Fosi. I then delve into my impressions of this slick little device plus a comparison with the higher priced and highly adjustable Qudelix 5K DAC/Amp with an internal rechargeable battery.What I like about the Fosi:pocket friendlywell builtintuitivesimple and inexpensivesolid upgrade for properly fitted IEM use in noisy environments.What I don't like (and why I knocked off one star):the Fosi is a power hog on a new iPhonecheesy USB C to USB C cable needs immediate replacementThe IEM gear I used with the Fosi (I keep my IEM's in Pelican cases for protection, they are NOT stock):Ziigaat Odyssey IEMMoondrop Dusk IEM (Crinacle)7HZ Timeless IEMiPhone 16 pro - new as of 4/25Tidal streaming app for iPhoneThunderbolt 5 Cable high Speed 80Gbps Data Transfer,16K/8K/4K type c to type cThe little Fosi adds depth, bass, timbre and soundstage to all 3 of the aforementioned IEM's which are all considered best in class for the price on the Hangout Audio website curated by the wizard of IEM's "Crin" or "Crinacle" aka Corin Kohn.I used the Fosi and interchanged my various IEM's at the gym every day which may appear initially to some as a loud and semi-absurd place to review IEM's and small DAC/Amp.In reality, it's ideal because noisy gym replicates the worst of the real world and puts IEM's, the ear bud tip choice and a DAC/Amp to a strong acid test. The Fosi passes for its low price point, dynamics and simple connections which are USB C to USB C in my case, and I bought a top-quality aftermarket USB C to USB C cable because the included cable is chintzy.One key here about ear bud tips - cheap, ill-fitting ear bud tips can make even a top rate DAC/Amp sound bass free, with thin mid-range and a tinny high end so get good quality proper fitting tips before you blame the Fosi or other DAC/Amp for garbage sound.Be aware of two simple facts about the Fosi. Fact one is that it uses source battery power (iPhone battery in my case) and it has volume buttons +/- that act independently of the iPhone volume buttons.The Fosi power drain is significant. 2 hours of Fosi use with my nearly new iPhone 16 pro drains the battery from 100% to about 84%. When using just an IEM for 2 hours, I get a 4% power loss from running Tidal and negligible power loss when using a Qudelix 5K DAC/Amp that has a rechargeable onboard battery.The Fosi onboard volume buttons sound like a silly thing to talk about but you can have your iPhone volume wide open and the Fosi volume set very low and get terrible Fosi performance. Adjust both the Fosi and source volume appropriately.I show a couple of photos of the Fosi next the slightly larger Qudelix 5K DAC/Amp. The Qudelix is about $100 on sale on Amazon but it's next level for total audio control because it includes a 10 and 20 step equalizer, a terrific app and a mind-boggling amount of audio adjustability for any headphone or IEM.The Qudelix allows for wildly expansive audio tweaking but it's complex and the Fosi is simple. If you want plug and play, get the Fosi, if you want total mastery of your head related audio and are highly audio tech savvy, buy the Qudelix 5K.I hope this data helps you make the best in this category for your own needs.

Works great on my Pixel 9 Pro XL to drive Audio-Technica ATH-R70x reference headphones (with balanced cables) which have very high impedance (470 ohm), requiring more voltage to drive. This impedance is slightly above the specifications that this DAC is rated for (16-300) but it is still able to provide good volume with fantastic clarity. I also tested with Dan Clark Audio Noire X (with unbalanced cables) which is slightly lower impedance than this DAC is rated (13 ohm) and it still performed excellent, however volume needed to be closer to the top of the range on both source and the DAC. This DAC did not have noticeable power draw or heat when driving the ATH-R70x, but it definitely warms up slightly with the Noire X. The build quality feels premium, though I wish it had some kind of volume level indication. Overall, the Fosi Audio DS2 is a fantastic value in a highly portable package, capable of driving a wide range of headphones with excellent fidelity.