This mini desktop DAC/headphone amp is custom-designed based on customer feedback. It features the high-end ES9038Q2M DAC chip, supports USB and optical decoding, and can handle up to PCM 32bit/384kHz and DSD256. This ensures a detailed reproduction of music, offering a clear and pure sound quality. Whether used as a DAC/headphone amp or as a preamp for an amplifier, the SK02 is an ideal HiFi companion.
About Fosi Audio
Fosi Audio is dedicated to developing and designing HiFi products that are "reasonably priced and emotionally resonant" based on user feedback. Adhering to a user-centric approach, and offering a 2-year warranty on each product, Fosi Audio has won sincere recognition from a wide range of audiophiles and well-known media personalities in Hi-Fi forums and social media sites.
Pros: Great build quality
Amazing looks
3.5mm and 4.4mm output options
Quality feel on the knob and buttons
Various input options
Great power output
Compact form factor
Excellent price-to-performance
Cons: Could have better-looking packaging, but that’s the only thing I can think of.
A huge thanks to @fosi_audio for providing me with the SK02 DAC for review purposes. However, my opinions remain unbiased and my own.
Testing Duration
15 Days
Tested With
Simgot EM6L
Simgot EW200
HIDIZS MS-1
TruthEar GATE
Specs:
What‘s In The Box？
Fosi Audio SK2 x 1
USB Type-C cable x 1
Optical cable x 1
User’s Manual x 1
Unboxing
Design, Build Quality & Input/Outputs
The SK02 has a really nice and honestly unique design for a desktop DAC, offering a super compact form that frees up space on your desk without compromising quality. The body, faceplate, and knob are made with a full aluminum construction, featuring a semi-matte black finish that feels incredibly premium in hand. The knob offers a consistent, smooth scroll, while the buttons provide a satisfying tactile bump.
On the faceplate, there’s a row of LED indicators on the left— the first set shows whether you’re in high or low gain mode. The next row indicates your PCM frequency, and on the top right, you'll see the input mode. Below that, another row lights up to indicate if DSD mode is enabled and what sample rate you're using.
Moving to the front, you’ll find two outputs: a 3.5mm and a 4.4mm. On the back, there's the power/USB-C input, optical input, and a 3.5mm input. The bottom has a nice set of rubberized feet that ensure the unit stays firmly in place on your desk.
Overall, I really appreciate the premium and sleek design that the SK02 offers. Combined with excellent build quality, I honestly can't find a single flaw—it feels incredibly well-built throughout.
Summaries
Compact, premium aluminum design with smooth knob and tactile buttons.
LED indicators for gain, PCM frequency, input mode, and DSD status.
Multiple outputs and inputs with stable rubberized feet.
Knob
The knob has a smooth semi-matte finish, just like the rest of the body. While some knurling would have been a nice touch, there’s really nothing to complain about here. The knob has a smooth scroll with slightly defined notches, and honestly, it feels really good to use. Clicking the knob once works as a play/pause button, and holding it down acts as the power button for the SK02. Overall, I really like the premium feel of the knob, with the added functionality being a great bonus.
Summaries
Smooth scroll with defined notches, doubles as play/pause and power button.
Feels premium and adds great functionality.
Sound
When it comes to sound signature, the SK02 offers a fairly neutral tuning that leans slightly toward the warmer side. There’s no overly harsh emphasis on the treble or bass, allowing you to experience the true sound signature of the IEMs or headphones you connect to it. Personally, I don’t use headphones, so I can’t vouch for how well the SK02 performs with them. However, when it comes to IEMs, the SK02 offers more than enough power, leaving nothing to be desired.
Honestly, I’ve never heard my EM6L sound this good. Even when hooking up more affordable pairs like the GATE, they still sound way better—almost like they’re more expensive. This is thanks to the SK02’s ability to provide clean, clear sound without altering the tuning of the devices you connect, while offering plenty of power to drive any IEM out there.
Summaries
Neutral, slightly warm tuning with clean sound.
Drives IEMs well, making even budget models sound great.
Gaming
When it comes to gaming, I highly recommend the SK02. Thanks to its neutral tuning, there’s no emphasis on overly harsh sounds, allowing the tuning of your device to shine through. I found that the SK02 provides a really good and open soundstage in games, handling busy audio environments exceptionally well. You can clearly distinguish where a grenade is going off or where footsteps are coming from, even during chaotic gunfights with shots flying everywhere. There’s no muddiness in the sound, and overall it delivers a really clean and detailed audio experience, whether you’re playing esports titles or enjoying casual gaming.
Summaries
Clear, open soundstage; handles busy audio perfectly.
No muddiness, great for distinguishing in-game sounds.
Conclusion
In conclusion, I can wholeheartedly recommend the SK02 to anyone looking for a budget DAC, especially IEM users. I don’t see you needing anything more to drive your IEMs. It’s packed with features, offers outstanding build quality, and comes in a really compact size with a premium aesthetic that fits any setup. In actual use, the SK02 delivers amazing, clean audio in every situation and really stood out to me during gaming, providing crystal-clear audio cues. For the price—and even beyond—I can’t think of anything I’d recommend over the SK02. It’s simply an amazing device without a single flaw that I’ve found during my time with it, and it’s definitely going to be a staple on my desk moving forward.
Summaries
Great budget DAC, especially for IEMs.
Compact, feature-packed, and delivers clean, impressive audio.
Pros
Great build quality
Amazing looks
3.5mm and 4.4mm output options
Quality feel on the knob and buttons
Various input options
Great power output
Compact form factor
Excellent price-to-performance
Cons
Could have better-looking packaging, but that’s the only thing I can think of.
- Fosi Audio sent this unit to me in an exchange for an honest, unbiased review. Rest assured that this review will do its best to devoid from any bias/es as much as possible.
- I have not tested this with MQA files or MQA streaming since I don’t use MQA at all.
- The following remarks and observations shall be made and owned only by me.
- No monetary compensation is/was involved before, during, and after the period of creation of this review.
- I have only tested this with earbuds and IEMs only.
- Your mileage may (and always, will) vary.
Burn-in time: 5-10 hours per day, 10 days.
IEMs/Earbuds/Source used:
- Etymotic ER3SE
- Sivga Que
- Simgot EW300
- Letshuoer S08
- Tanchjim 4U
- Kiwi Ears KE4
- Kiwi Ears KE4
- Temperament X6
- Sony Xperia X Compact
- Aiwa XP-V710C CD Player (12 sec. EASS)
- Non-HiFi smartphone (Infinix Note 12 G96)
- Desktop PC, Laptop.
- Local Files via Foobar, YouTube Music, Deezer, and Qobuz with UAPP.
Setup configuration: Fosi Audio SK02 paired with phones/laptop/pc.
Just like its smaller, older siblings, the Fosi Audio SK02 presents itself in a neutral, nearly transparent manner. This can be a good or a bad thing depending on the user’s preference and pairing, and it paired well with all of my IEMs and earbuds. The SK02 is not as transparent as what the Tanchjim Space exhibits, especially on the upper frequencies, but it isn’t a deal-breaker, or even noticeable on its own for me to hear.
Build Quality:
Build quality is rigid, compact, and has a good amount of heft to it, for me to call it a desktop DAC instead of a “dongle”. I also believe that this is not meant or designed to be used as a dongle as well, due to its size and device compatibility (will be discussed later). Its size is also in and within the desktop DAC territory, along with the iFi Uno, or Topping DX1 in terms of size.There are the ports that you usually see in most desktop DACs as well, such as optical and out ports, aside from the usual 3.5 and 4.4mm ports.The SK02 is operated with two buttons, which are the gain and mode buttons. There are also plenty of LED indicators here as well which tells the file type being used, its bitrate, on and off, mode, and a “real time indicator). This desktop DAC is controlled with the use of its volume knob, that also acts as a play/pause/mute/unmute button when pressed. Its volume is also independent from the software volume and can be controlled precisely since it has a bit of soft “clicks” when turned. Overall, I do not have any problem nor encountered any problems when using the Fosi SK02. However, if I were to nitpick, it would be its volume knob, because I am used to volume knobs having a “tactile” volume limiter on both ends of the volume level, which this do not have.
Device Compatibility:
I am unable to use the Fosi Audio SK02 on my phones due to its high power requirement. I have already anticipated this way before due to its specification, so I am not surprised that this happened on my end. Laptops and Desktop computers will connect with this USB DAC with no problems since this USB DAC is plug and play and does not have any bundled software with it. As for the tablets, It can be a hit or miss depending on the brand. Huawei tablets do not work with this USB DAC, while Samsung Tablets pair with this dongle with no problem. I haven’t tested this on iPads.
Battery Consumption:
This desktop DAC requires more battery juice when compared to the usual USB DACs. It consumed around 50% of the battery of the Samsung tablet I have tested with after 3 hours of usage. This added to my conclusion that the Fosi Audio SK02 is designed to be used with desktops or laptops rather than being used as a portable dongle.
Power and volume:
This is where the Fosi Audio SK02 shines - its power output. I had no problems pairing this with any IEMs and earbuds I have with me. Whether it be easy to drive or hard to drive planars, the Fosi Audio SK02 will handle it well, due to its two gain modes and precise, tactile volume knob. Here are the IEMs I have tested with this USB DAC and the volumes required for me to drive them properly:
The Fosi Audio KS02 is the “best” Desktop DAC I have auditioned under 100 USD, in terms of overall sound and build quality. This does everything that a desktop DAC should do well, the first one being able to pair well and enable the IEM/Earbuds to perform to its full potential, price considered. I also have a theory that this also will pair well with some headphones, but I will leave that for the other reviewers to test and find out. A friend of mine even said that this is quite “overkill” for a desktop DAC for this price point, which I mostly agree. This definitely stands out under 100 USD in my book, Fosi Audio!
Who is the Fosi Audio SK02 for?
For those people who want and need a neutral, nearly transparent sounding DAC under 100 USD.
For those people who have a variety of IEMs and earbuds but do not want multiple sources.
For those people who want a reliable, plug and play Desktop DAC.
For those people who need a DAC with an optical connection.
For those people who want a sturdy, dense, desktop DAC.
For those people who want a physical volume knob.
Why should you not buy the Simgot DEW4X?
If you prefer a portable DAC.
If you need and prefer a warm-sounding DAC.
If you need a DAC that needs to be paired with a phone.
If you need a dac that has an app or an EQ built-in.
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Thank you for reading!
People looking for a powerful, clean but affordable source
People looking for neutral source that improves the best parts of your headphones
People looking for a feature-rich source
People looking for the best value source in the market
WHO THIS UNIT ISN’T FOR
People who want a portable source
People who want a more colored source
People who want a source with better phone compatibility
People who want a more traditionally shaped source
SHORT REVIEW:
I cannot think of any major cons with the SK02 that bars it from being arguably the best desktop source to get in 2024. Insanely high output, rich features and a superb sound that enhances everything I plug into it with enough power to drive anything. Maybe you’ll take issue with its compatibility, the shape or the lack of RCA, but as someone who’s been searching for the one source I can use to not only review but listen to music, the SK02 lived up to my expectations and more. HIGHLY RECOMMENDED
FULL REVIEW
In the world of portable dongle DACs littering the market, it’s hard for desktop jockey's like myself to find a reliable all-in-one device to power everything that I have with enough driving force and a clean output at a reasonable price.
That was until Fosi came along and released the Fosi SK02. But what exactly makes the Fosi SK02 the best budget desktop DAC/AMP in the market today?
DISCLAIMER:
Big thanks to Fosi for sending over the SK02 in exchange for my honest thoughts.
CLEAN SOUND, AFFORDABLE PRICE
As someone who has been searching for affordable, high quality and powerful sources, Fosi has always been under my radar for seemingly being the only brand that can offer all three in the market. Maybe it’s their marketing, but all other brands I’ve seen have fundamental flaws in the products I’ve tried that make it somewhat iffy to not only use but recommend to other people. Whether it’d be awkward volume shifts or an insanely inefficient and noisy sound, it’s a truly rare sight to see a brand come up with a fundamentally good source. So when I heard that Fosi was coming out with a combo DAC/AMP that can do 1100mW on 4.4mm Balanced for under $100, I just had to bite and taste what a package deal Fosi seems to be offering.
SPECIFICATIONS:
Model SK02
Input USB/OPT
Output 3.5mm Headphone,4.4mm Headphone,3.5MM line out/OPT
Amp output maximum power 3.5MM：
High Gain: 280mW@32Ω, 130mW@64Ω, 40mW@250Ω, 30mW@300Ω
Low Gain: 90mW@32Ω, 50mW@64Ω, 15mW@250Ω, 10mW@300Ω
4.4MM：
High Gain: 1100mW@32Ω, 550mW@64Ω, 150mW@250Ω, 120mW@300Ω
Low Gain: 350mW@32Ω, 180mW@64Ω, 50mW@250Ω, 40mW@300Ω
Frequency Range 20Hz-20kHz (±0.02dB)
THD ≤0.001% @ 1kHz
SNR 3.5mm Headphone:
Low Gain:116dB
High Gain:120dB
4.4mm Headphone:
Low Gain:110dB
High Gain:115dB
Headphone matching impedance 16-300Ω
PC-USB Sampling Rate 32Bit/384KHz DSD256
OPT Sampling Rate 24Bit/192KHz
DAC Chip ES9038Q2M
Device Dimension 4.76*2*1.69inch (121*51*43mm)
Net Weight 0.84lb/380g
Power Supply 5V, USB Type-C
BUILD
The SK02 is arguably the most unique desktop source that I’ve seen in a while due to it’s somewhat peculiar shape. While most sources are flatter and wider, the SK02 is taller and thinner with a somewhat brick-like shape.
Starting on top, you can find the bulk of the features of the SK02 with the Fosi logo up top, two buttons with the left changing gain modes and the right changing connection modes, the plethora of LEDs with the left side showing your current gain mode and your PCM decoding and on the right with the connection mode as well as your DSD decoding and power/volume status. At the very bottom is the massive infinite volume knob that also acts as a universal pause button by pressing down on the volume.
Moving down to the front side of the device, you can find the 3.5mm and 4.4mm jacks.
The sides are bare with just a solid aluminum panel wrapping them.
The bottom features the rubber stoppers.
On the back, you can find the inputs including the Type C, optical and AUX/Optical out.
While the build might not be so different from other desktop DAC/AMPs, the construction is sturdy and the interface is well-made. I don’t feel scared to wear out the jacks and the buttons feel tactile and satisfying. The knob infinitely spinning might be a problem for those who want a true analogue knob, but I’d say that it does the job really well and allows for a very fine level of volume adjustment. Plugging in jacks have a very satisfying click, especially on the 4.4mm which fills me with confidence that this won’t wear out quickly.
FEATURES
One of the most surprising things about the SK02 is how much features this thing has for a sub $100 desktop amp.
Firstly, you get the aforementioned gain switch that allows you to change from low gain to high gain. The difference is VERY audible on both and can mean the difference between being able to drive something comfortably with good headroom and not having enough power.
This is thanks to the over 1100mW of power on high gain through the ES9038Q2M DAC and SGM8262 AMP and balance that makes the SK02 one of the best combo DAC/AMPs to drive high impedance and low sensitivity headphones. Besides dedicated amps, I don’t know other DAC/AMPs in this price range that has that high of an output.
You also get your usual mode switching from optical, USB or coaxial for those who would like to plug this into home theater setups.
But arguably one of the best features of the SK02 is how much information it provides on the top LED display. PCM decoding, gain mode, input mode, DSD decoding and power inputs are exactly the kind of information you wanna see while listening to music. This made me realize that MusicBee does NOT decode higher than 96kHz PCM on its own but Foobar with the SACD plug-in does. Being able to know what gain mode and connection mode are also very useful when troubleshooting or testing different gears. The argument could be made that they could’ve just made it more compact and just use different LED colors to indicate these things, but I’d argue this makes it easier for someone to know exactly what they’re playing.
You can also use the volume knob as a pause button that works surprisingly well for even applications that usually can’t get paused by the system. From foobar to MusicBee, if I pressed the volume button down, it will pause the music.
SOUND
As someone who’s spent their time on portable dongle DACs as their main source for both mobile and PC and having only experienced a handful desktop options, the SK02 seriously impressed me with how much it opened out the sound of anything I plug into it. This is further compounded by the option to have a balanced output that makes this a seriously impressive source in both sound and power.
First off, the sound is properly neutral. I didn’t find this to color any of the headphones that I plugged into it. However, it does improve upon the strengths of whatever I plug into it. It opens up the sound and presents the soundscape in a cleaner, more transparent and nuanced way that is nothing like I’ve heard in any other source. I’ll explain more when I compare this to other sources, but I was ge nuinely impressed with the headroom I got with this and how much it improved everything I plugged into it.
Arguably the strongest sonic feature about the SK02 is how much it improves the dynamic range of the headphones I plug it on. The nuances in music, especially when listening to higher resolution files are evident with how the nuances are more prominent and the space in between instruments make music sound more immersive than other sources that I’ve tried.
This is further compounded when using the 4.4mm balanced as it opens up the sound further and gives you even more headroom and provides a very immersive listening experience unlike anything I’ve heard prior.
Pairing
Normally, I have a favorite pairing for the sources I review. However, the SK02 is the one source that I found to pair with basically everything I throw at it. From the humble in-ears to my 500ohm beast of earbuds, the SK02 is more than capable of providing sufficient and clean power to give me a satisfying listening experience. I can pair almost anything with the SK02 with little to no issues, so pairing is very versatile.
Noise
Despite outputting almost 1100mW, I never experience any issues when it comes to noise floor on even very sensitive IEMs on balanced output. I paired the SK02 with the Simgot EW200 with a balanced cable and I did not hear the noise floor.
USABILITY
From the moment I set-up the device to the hours of listening I’ve put into it, the SK02 has given me a hassle-free and versatile experience as I often never have to think of anything after plugging whatever headphones and adjusting the volume accordingly. No complex instructions from the manual, no fumbling with the cables, buttons or connectors. Just the perfect definition of plug and play.
I really appreciate Fosi sticking purely with USB audio for both power and data as adding another power supply will just cause problems if you don’t have an outlet ready. Despite that, they were still capable of provide 1.1w of power in the measly 5V DC. At that point, it’s inexcusable how other companies can’t achieve that level of power and sound cleanliness in the budget segment.
The one thing that I will say that someone both impressed but bothered me was the form factor. While I do think that this form factor is great for those who want a slimmer footprint, the height forced me to place the SK02 elsewhere due to its height and not being able to fit into my desk without obstructing my monitor. I know it’s a niche problem, but it’s something to consider if you put your sources on your risers or in between areas.
Otherwise, I found 0 issues with the SK02 in my weeks of listening. I could not think of a single con of this product for the price and perfectly compliments everything I plug into it.
COMPARISONS
First, let’s compare it to two of my other desktop options. The Topping DX1 Combo DAC/AMP and the combo of the NEOHIPO DC10 and Douk U3.
vs Topping DX1
Prior to the SK02, the DX1 was my main desktop source. For the time, it was the best source I’ve ever had as it brought about the best in the IEMs and headphones I plugged into it with superb quality and headroom. This was when I realized that desktop sources were a completely different beast from the little dongle DACs I was used to.
Come today and I realized that the DX1 wasn’t even the best I could get in the budget. The SK02 provided a cleaner, more dynamic and more open listening experience compared to the DX1. The DX1 had a warmer tone that provided a more natural timbre and paired better with neutral bright headphones, but the SK02 was able to provide a more transparent listening experience while improving upon the dynamic presentation and cleaning up the transient response.
But arguably the biggest upgrade from the DX1 was raw functionality and features. The DX1 is just a DAC/AMP through and through. You get your analogue volume knob and a gain switch at the back, but that’s it. The SK02 has dedicated LED for decoding, gain modes and power all in the same side. No fiddling at the back to change gain modes. The DX1 does have RCA connection going for it, so you can use it as a DAC to pair with your headphones while the SK02 is limited to being used as a pre-amp through the AUX at the back.
On top of that, the SK02 features both a 3.5mm and a 4.4mm output that can do 280mW @ 32ohms on 3.5mm and 1100mW on 4.4mm Balanced. Compare that to the DX1 that only features 3.5mm and maxes out at 280mW, you start to see why the SK02 is just the superior source in general
While the DX1 has a place in my heart, I cannot deny that the SK02 is just the better device overall. More features and a more powerful sound at the same price makes the SK02 the clearly superior choice.
vs Neohipo DC10 + Douk U3
This set-up is a newer set-up of mine as I wanted to get a really powerful source to pair with a nice pure DAC.
First things first, the SK02 wins in pure convenience. The amount of setting up you have to do to is something only enthusiasts would find enjoyable. You need to find a free outlet for the Douk U3, a decent RCA to connect the U3 to the DC10 and the USB that eventually plugs into the PC. The SK02 just needs you to plug and play. The space you need to setup both devices might also be a problem for some, but both devices are pretty small and you can stack them on top of each other to minimize the amount of space being taken.
As for features, the DC10 may have a very simple display but the tactile levers and straight forward dual LED indicators are perfectly adequate, albeit will require you to thoroughly read the manual to know what color is which. The U3 has an on and off switch at the back and an analogue volume knob. Unfortunately, this volume knob is borked as the sudden jump in volume means that this is practically unusable with in-ears.
The issue with the volume isn’t the only reason why this combo isn’t great for in-ears as the noise floor of the U3 really cannot pair with in-ears well. On less sensitive in ears, it’s perfectly adequate and actually enjoyable with the likes of the KZ PR3. But anything more sensitive than 105db and lower than 32ohms will just be a noisy mess. I understand the DC10 has basically nothing to do with that and I can use an op-amp to improve the noise problem a little bit, but the SK02 commits all those issues in a single, convenient package.
The only benefit to the U3 + DC10 combo is that you can essentially change either to improve your listening experience. Want a cleaner sounding amp to something cleaner, more powerful or has tubes? Replace the U3. Want a more feature rich DAC? Replace the DC10. But that means going out of the $100 budget that the combo asks for which goes higher without sales.
At that point, the SK02 is just the better device for those who just want a good source and nothing more. The combo source is great for those who like to DAC/AMP roll or want to think of the long term when one of the parts die and needs to be replaced. Versatility is also the strength of the combo, but at what cost? I’d personally just take the SK02 and call it a day, but I get the appeal of the combo and is still a viable choice for hobbyists.
CONCLUSION
Whether you’re a casual listener or a power user, the SK02 might just fit into your set-up to have the best listening experience. A near seamless user experience paired with a very powerful output that rivals dedicated amplifiers that require a separate power supply isn’t something you see a lot, moreso under $100.
If we’re talking hard flaws, I really cannot think of anything that the SK02 is flaunting. Lack of mobile support? Get a dongle instead, there are many powerful portable dongles in the market today. Height? That’s justified, but it’s also slimmer than your usual desktop DAC/AMPs, so unless you have literally no more space anywhere else, the SK02 is genuinely the perfect budget reference desktop DAC/AMP you can get for under $100 today.
I have placed my order as I own a couple of other Fosi devices and very much like the sound and build. One thing I haven't found is whether the SK02 is powered by external wall wart or by source USB. It seems unlikely that power supplied by the host source would be able to output the 1100 mW listed in the specs.
I have placed my order as I own a couple of other Fosi devices and very much like the sound and build. One thing I haven't found is whether the SK02 is powered by external wall wart or by source USB. It seems unlikely that power supplied by the host source would be able to output the 1100 mW listed in the specs.
I have to say, this is truly the perfect tool among office desktop DAC headphone amplifiers—no unnecessary ports, the most practical features, and the best price.
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