WATCH FULL REVIEW HERE:

PROS

• One of the best desktop sources under $100
• Very high power output for the price
• 4.4mm Balanced Output for sub $100 desktop amp
• 1100mW on 4.4mm balanced
• Clean, neutral tone with no coloration
• Improves transients and dynamics drastically
• Immersive headstage and imaging performance
• Perfect headroom for most gear
• Solid build quality
• Very informative LED presentation
• Solid features
• Interesting form factor
• High quality interface
• Intuitive layout

CONS

• Phone compatibility
• No RCA input
• Non-traditional shape (nitpick)

WHO THIS UNIT IS FOR

• Anyone looking for a good quality desktop source
• 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. 

Thank you for reading my full review on the Fosi SK02. If you would like to order one, consider using the non-affiliated link below:

https://fosiaudio.com/products/fosi-audio-sk02-desktop-dac-headphone-amp