I ordered this mainly to breathe new life into an old surround stereo I own. Very high quality with so many manual equalizers, but due to its age, it doesn't accept digital input. More specifically, my plan was to connect the optical output from my receiver to my older stereo, and this converter did the trick.So, my older stereo only takes analog RCA L/R input. I was able to cover my digital audio to analog RCA and get it on the stereo. The quality is very good. I'm actually quite impressed. I mean, my stereo has a very high-quality output, and that's exactly why I wanted to use it. But I just assumed covering digital to analog will have enough impact on the reduced output that you can clearly notice it. But that's not the case with this converter.So, the one really interesting feature that I wasn't planning on using but ended up using and enjoying is the dedicated powered subwoofer output. I ended up connecting an external sub, and oh boy, that made so much difference.There's not a whole lot to this unit. It's simple and does exactly what it needs to do, with great quality. If you need a digital-to-analog audio converter, this is definitely a great choice.

Works as I needed it to.

I own multiple Fosi Audio products and find their build quality and chip choices to be great value (and great sound!). This DAC also does not disappoint in that regard, sounding clear and LOUD when outputting USB from my PC or Optical from my CD player and/or my TV. It's also nice and compact and works well in a "stack" with other mini components (in my case a Douk Audio T3 Pro phono preamp and a Fosi Audio ZA3 speaker amp). However, it makes a mechanical click every time an audio stream is detected/engaged, which is audible up to a few feet away. Because of this, I found it very distracting placed next to my PC at my desk, so I instead decided to use this DAC with Optical out from my TV, into my passive speakers. Since it's now > 6 feet away, I don't hear the clicks and am getting great TV sound from this DAC. Recommended, but also recommend Fosi revise this model to soften or remove the clicks!

The FIO has become simpler and clearer

I've been a long time FOSI Audio user, having purchased a variety of different audio components, ranging from DAC's to various power amplifiers, over the past 5 years. And given their varying price-points, I've been quite happy with most of them.So when the Q6 DAC was announced, I just had to have it. When it arrived, I was gratified to find a simple layout, sized similarly to the V3, P3, and P4. To begin with, don't assume that the Q6's big knob is a volume control knob, because it's not. The knob is a simple input selector between USB, Optical, and Coaxial. To the left is the on/off switch - it's that simple. So it's not a preamp - just a simple, straight-line DAC. It also doesn't require a separate power input - the USB cable sufficing as the 5V input when using the USB input. If you're using optical or coaxial, then yes, you'd need a 5V power supply that has a USB-C end going into the DAC, and a USB-A connection on the other end that you can plug into an AC adapter. Because I have several powered subwoofers with crossover frequency adjusters on the rear, there was no need for me to try the subwoofer output on the A6, so no comments will be made about that.One other "welcomed" variable on the Q6 is that changing out the single op-amp inside (the stock being the NE5532 that you see everywhere) is rather simple. You just unscrew the left and right rear screws (without having to remove the front knob at all), and the interior board slides right out. Takes less than a minute. It's not as instantaneous as the DOUK Audio A5 amplifier that has a glass lid on the top that you just raise to insert/remove op-amps, but it's the closest that Fosi has come to ensuring that op-amp changes come easy.As for trying different op-amps, I experimented with 5 different models (the ones I had on hand) - those being the IC-based MUSES02, the OPA2604AP and the LME4972NA, along with the discrete BURSON V5i-D and the highly reviewed discrete SPARKOS LABS SS3602. I've long since stopped using the stock NE5532's that you find in most Chi-Fi units.I initially used the Q6 by itself, electing to control the volume via the FOSI Audio ZA3 power amplifier. What I found a bit surprising is that the gain on this Q6 is set quite high, and I had to keep the volume knob on the FOSI Audio ZA3 to about 8 or 9 o'clock position just to maintain normal listening levels. After trying the Q6 by itself, I then connected it to the budget (yet very competent) FOSI Audio SK01 head-amp/preamp, and that really helped in taming the high gain of the A6. In addition, the SK01 also helped balance out the overall sound because just using the Q6 alone, I felt the bass output was so prodigious that I had to crawl under my desk to turn my powered subwoofer down. I love bass, but the Q6 brings it to another level, that's for sure. Attaching the Q6 to a preamp/head-amp helps in this regard. As an aside, I have an order in from the FOSI Audio website for the P4 (which is backordered), so when that arrives, I'll be curious to mate the Q6 with that one.Alright - so how does it sound? In a nutshell - very good, given such a low price range. The Q6 is very dynamic, and I found that by itself, it had a very smooth sound - as if you were listening to tube gear. But for me - subjectively speaking - the overall sound characteristics were entirely too smooth for my tastes, and pairing it with the highly competent, budget FOSI Audio SK01 brought everything into balance, providing additional detail, while still retaining much of the smoothness. In addition, coupling it with the SK01 helped tame the bass somewhat. The bass was now still very deep, but not overwhelming, as it was balanced with the mids and highs and not trying to take over the scene. Audiophile descriptors to describe the Q6, would include "highly linear for such an inexpensive component, good sound-staging, powerful bass, attractive instrumental timbre, immersive (depending on what you're listening to), and so much more.My listening for this particular review included a variety of classical music (large orchestral and small chamber ensembles), jazz, and big band jazz. I've long found that to truly evaluate audio gear, listening to a variety of different instruments provides excellent test material. I auditioned the Q6 connected to several amplifiers - the FOSI Audio ZA3, the DOUK Audio A5, the SMSL DA-9, and the FOSI Audio V3 Mono-blocks. Speakers used were the KEF Q150's and Q1 Meta, Wharfedale D320's, along with active 8" Presonus and Mackie subwoofers. Cables (for speakers, USB, RCA, and balanced) used included versions from Audioquest, World's Best Cables (WBC), and Blue Jeans cables (BJC). DAC's compared against were the iFi ZenDac II, JDS Labs Atom+, SMSL SU-1, Schiit Modi 3+, and the FX-Audio DO1. All listening was done on a desktop, near-field environment with my being situated 3-4 feet away from the speakers.At this point, some of you might be wondering, "Which op-amp sounded the best?" Surprisingly, all the ones I mentioned above sounded fairly good. For me personally, I found the SPARKOS LABS SS3602 discrete op-amp the winner of the group, with a superior tonal balance, sound-staging, and realistic instrumental timbre. And again, the Q6 has only 1 changeable op-amp, so any op-amp you purchase hopefully won't break the bank. I did have to take a few days to accurately come to that conclusion, but any one of those op-amps mentioned would do fine. However, If I had to rate them on my system based on audio qualities, I'd rank them in the following order:1. SPARKOS LABS SS3602 (discrete)2. MUSES 02 (IC based)3. BURSON V5i-D (discrete)3. OPA2604AP (IC based)4. LME4972NA (IC based)So why did I only give the Q6 4 stars, you may ask? Quite simply, due to the constant clicking sounds. When the music comes on, the Q6 clicks, and when the music ends, it clicks again. Even if you pause the music, it clicks, and when you unpause/play again, it clicks again. Then, even though your next music selection might only be 5 seconds away, it clicks again when the next piece is played. You get used to it, but if FOSI Audio wanted to include some sort of internal setting that puts the Q6 into standby after, let's say, a time period of 15 minutes of inactivity (like some other amps do), that would have been OK. However, to have it click every time music starts playing, and then abruptly clicks when it ends, is a bit too much. But you get used to it, as I said. The clicking is not game-changer (for me, that is), but it is noticeable. Of course, for some, this might be a game changer - who knows?This brings me to a recommendation to all Class D amplifier manufacturers, and that is to incorporate firmware update capabilities in your power amplifiers, and perhaps other components. Nowadays, there are firmware updates available for everything - TV sets, cameras, DVD players, streaming boxes, cell phones, appliances, etc. So why not begin to make this capability available in your class D amplifiers also? After all, we're talking about chip-based amps here. Think about it. If Fosi (and others) start making firmware updates available via USB inputs, performance parameters could be updated or corrected in minutes. And rather than having to resort to releasing new products - in what seems like every other month just to stay competitive - the manufacturers can incorporate firmware updates to improve technical aspects of their gear. This alone would be a huge selling feature. C'mon guys - this is the future, and you should consider this. For example, I'm surmising here that there could even be a "fix" via firmware for the clicking sound mentioned above, to mention one area.In closing, you can't go wrong with the Q6, and sound-wise, I'd have to say that it is competitive against DAC units that cost between $200 and $250 - so that makes it a winner to be sure.As I always say, reviews are subjective, and no two folks will typically agree. I recommend keeping tabs on future FOSI Audio releases over the next year or so. The most recent audio/electronics show had FOSI showcasing some much anticipated audiophile products to include (surprisingly) bookshelf speakers, a balanced preamp to compliment their ZA3 (I'll get that one for sure), along with new mono-blocks, and more!. Do expect that prices will rise with this new gear, and not just due to any tariffs, as FOSI had price increases previously planned because of the audiophile level qualities of those new, pending components. Over the past few years, FOSI Audio has garnered a growing list of loyal followers, and I'm starting to become one of them also.