Fosi Audio K7 Review

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Everyday Use

Like the Q6 and V3 Mono Amp before, as a dedicated desktop solution, the Fosi Audio K7, is simply perfect. Apart from one, minuscule drawback, but more on that later.

The large volume knobs, the sturdy connectors, the wide baseplate all of that made the DAC almost glued to my desk, despite its modest weight. Even plugging or unplugging sources could (almost) be done with just one hand, which isn’t always the case with small devices like this one.

Once again, I plugged three sources to the K7 – Macbook (USB), PC (Optical), FiiO DM13BT (Coaxial) – and switching between them was swift and fast thanks to its clever design and surprisingly nice screen. In fact, before everything else, this was the main attraction once powered on: the screen.

Tiny (1.5 inch) and monochromatic, I was still amazed by how clear and crisp it looked in real life. Divided in three section – upper for the mic/bypass/UAC information, left side for the sample rate, right side for the type of input – the panel exceeded all my expectations and remains readable even under the daily light, giving me informative feedback whenever I needed.

Sure, Fosi could have done without, the control buttons being more than enough for that but, for me, this was one of the coolest features they embedded into the K7.

Same could be said for the two volume knobs, the DAC answering as quick as the wheel turned, allowing me to finely adjust my headphone volume, and the gain level of my microphone – perfect for my weekly teams meeting. Quick note about the microphone though: it only works if you stick to UAC 1.0, UAC 2.0 automatically cancelling the microphone input function, even in basic 16 bit / 44 kHz mode.

Still, thanks to its complete I/O and small chassis, the K7 found its place quite effortlessly in my office room, sitting right under my screen, linked to both my laptop and desktop pc, replacing the Q6 and SMSL DO400, then linked to my KEF LS50 Wireless.

Sadly, the new Fosi Audio lacking a subwoofer output, I had to connect my subwoofer (KEF KC62) to the speaker, limiting my control option this time.

And then, you ask, what’s the one flaw you mentioned then? The power plug! Not supporting USB-PD, the Fosi Audio K7 needs its own, 12V, power supply. Not a big deal on its own, but in an era where all and everything could be powered by the same all-purpose cable, the fact that you still have to connect a separate plug remains mildly uncomfortable for a device as tiny – but maybe that’s just me.

Apart from that, it’s almost perfect so let’s check the specs.

Specifications

For the nitpickers and nerdy ones here, I’m giving you the specs and technical sheet. For the rest, feel free to jump to the next section to see how the K7 performs in real-world listening.

XMOS XU206 + AK4493SEQ + OPA1612 + TPA6120

Marketed as a “HiFi and Gaming one device”, the Fosi Audio K7 employs a well-established combination of components, each selected for their proven performance in compact desktop audio devices.

Like the Q6, at its core you’ll find the AKM AK4493SEQ, one of the latest iterations of AKM’s VELVET SOUND lineup, capable of decoding PCM streams up to 768kHz and DSD512. Based on AKM’s updated design after the fire that impacted their production years ago, the chip offers superb dynamic range (123dB), ultra-low distortion (0.00007% THD+N), and – reportedly – AKM smooth signature

Upstream, handling all the digital streams, comes your usual XMOS XU208 — an 8-core controller that’s been around for a few years now, but still perfectly suited for this type of application. Not XMOS’ newest chip, but in practice, it’s reliable and perfectly functional for most desktop setups, ensuring stable transmission of high-res files (up to 384kHz PCM / DSD256), without introducing noise or latency, whether you’re running Windows, Mac, Linux or even mobile devices like an iPhone via USB-C.

Last but not least, for the analog stage, Fosi went with Texas Instrument’s excellent OPA1612 dual op-amp. An op-amp offering low noise, excellent linearity across the full spectrum, and a THD+N well below 0.00002% for keeping the signal clean before amplification. In combination, the Fosi audio K7 gets a set of NJW1119A + NJU72315, so to get the cleanest volume control.

Finally, for headphone amplification duties, the K7 relies on the well-known TPA6120 from Texas Instruments. A dual-mono setup delivering high slew rate, extremely low output noise and plenty of current available — allowing the K7 to deliver up to 2100 mwW @ 32Ω on the balanced output, and 600mW @ 32Ω on the single-ended jack. More than enough to handle virtually any headphone, from easy IEMs to full-size planar magnetics, while keeping background noise impressively low.

Numbers?

• Up to 121dB of dynamic range on the balanced output
• THD+N as low as 0.0002% (balanced)
• Noise floor under 2.5μV on SE, and 6.5μV balanced.

Bundle – Inside the box

Simple, but not too bad, the Fosi K7 still comes with the bare minimum – or almost. In the box, you’ll find:

• the Fosi Audio K7
• a USB-C to USB-C cable, with a USB-A adapter attached
• a 12V power supply
• a clever microphone male + headphone male to combo female input
• some documentation
• and… that’s it

So yeah, the very minimum, which means you’ll have to get your own set of analog/digital cables, but considering the price and the fact that Fosi gives you an adapter and the USB-C cable, I won’t complain too much this time.

For the nerdiest one, here is the full technical data, for the rest, you can go to the next page already.

Technical Data

• Type: DAC
• Model: Fosi Audio K7
• DAC: 1x AKM AK4493SEQ
• Low Pass Filter: TI OPA 1612
• USB Chipset: XMOS XU208
• Amplification: 2x TI TPA6120A2 + 2x OPA1612
• Frequency range: 20Hz – 20 000Hz
• Compatibility: PCM up to 32bit/768kHz – DSD up to DSD512
• SNR: 121dB (Balanced) / 122dB (single ended)
• THD: < 0.0002% (Balanced) / 0.0005% (Single Ended)
• Line level: 2.0Vrms
• Size: 50 mm x 155 mm x 90mm
• Weight: 700 g
• Inputs: USB-C, Toslink, Coaxial, Bluetooth
• Outputs: RCA, Jack 3.5mm, Pentaconn 4.4mm
• Power input: 12V
• Price: $229,99 USD

Sound Performance

For the purpose of this review, I used the Beyerdynamic DT900 Pro X, my good old Audeze LCD-X, and the fantastic Shanling HW600 (one of my favorite headphone)

For the source, I used my own computer, Apple Music and Qobuz for Hi-Res files, Spotify for low-res, and some old CD with the fantastic FiiO DM13BT.

Overall signature

So, how does the Fosi K7 fare against the competition?

If you just want the short answer: for the price, this is easily one of the most impressively neutral entry-level DAC/Amps I’ve tried in a while—right up there with the SMSL DO400 and honestly giving a hard time to classics like the iFi Zen DAC series.

Compact, user-friendly, and all-in-one, the K7 stays true to its promise: transparent, dynamic, and clean, with just a hint of added versatility thanks to its EQ options.

Now, for those who like to dig deeper, if the Fosi Audio K7 can be set as just another “set-and-forget” desktop DAC/Amp, this would be missing the point – the DAC/Amp being like real Swiss Army knife for budget or minimalist setups.

Not only did it pair admirably with my FiiO FA19 – lovely pair by the way, it was also capable to drive my Audeze LCD-X or my old Meze Empyrean, without the slightest hint of stress.

Same with the Hifiman Svanar – a notoriously difficult to drive IEM that I keep for this purpose – which the K7 handled with absolutely no sense of struggle, even on tracks with huge dynamic swings. Sure, you could get more powerful solution like the Hifiman EF-600, but compared to its size, I do think that the K7 is one of the most impressive DAC/Amp combo I’ve encountered recently.

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