FiiO K9 Pro ESS Review

DAC Performance

The K9 Pro ESS impressed me a lot in terms of performance. First of all, let me state that I listened to the entire product range of FiiO, except for the M17, and it would not be wrong to say that this device offers the highest sound quality that FiiO has to offer. In this paragraph, I’ll be focusing on the DAC mode only. First of all, let me remind you that K9 Pro ESS uses two of the critically acclaimed ES9038PRO flagship dacs. The characteristic feature of this chipset is that it offers a very flat, colorless, detailed, and linear response when implemented well. This is exactly what I hear from the K9 Pro ESS. 

The DAC reflects everything as it is, bit to bit, note to note. I tried it with various setups, but the outcome did not change. It offers brilliant detail retrieval, you can hear the problematic parts of poorly recorded tracks, which is not something most people prefer. However, that’s exactly why I like K9 Pro ESS. It is a great DAC that does not saturate or manipulate the signatures of your equipment. It offers excellent tonal balance, excellent resolution, and technical capability while doing so. The timbre, the tonality of the instruments feel accurate and the clarity is just damn impressive. Whatever FiiO did to get here, I expect them to continue pushing forward.

The K9 Pro ESS easily rivals some of the bests in my inventory. The K9 Pro’s DAC mode sounds as good as the Topping’s D70S, a brilliantly successful dedicated DAC that retails for $649 and doesn’t offer the AIO flexibility that the K9 Pro ESS does. All reviews are written by taking into account the price factor, no matter how good the product is. It is obvious that the price-performance ratio is important for all of us. The competitive pricing of all-in-one units is hard to come by, however, somehow FiiO is managing to sell this unit at around $850 USD. If you’re even slightly familiar with the DAC market, you’ll find that any product that includes a dual ES9038PRO and toroidal power supply is easily priced at over $1000 USD. In my opinion, the impressive point here is that FiiO is pricing a feature-packed all-in-one device with excellent quality components for under $1,000.

DAC & AMP Performance

You already know that the product has a great DAC stage, and uses a very clean power supply accompanied by a complex filter system that purifies noise, jitter, and other elements that pollute the signal. Well, let’s take a look at what can be said about the AMP stage, shall we? FiiO preferred OP-AMPs with a slightly warmer timbre like the OPA1612 and I think they wanted to deliver a slight, magical touch to the flat and linear response of the ES9038PROs. When we switch from DAC to AMP mode and listen, it is not easy to perceive the difference right away, especially with stereo equipment. Since both stages are well-implemented and we could only talk about the differences in nuances, I needed something that would show me these differences more closely and enable me to perceive them better. In such cases, of course, reference in-ear monitors or headphones are your best bet. 

The K9 Pro ESS sounds natural, detailed, and organic. This is where I fell in love with the K9 Pro ESS. It offers a top-of-the-line level of transparency, resolution, and detail retrieval while sounding organic with nearly all my IEMs and full-size headphones. They were dead silent, with pitch-black background and a timbre that feels accurate, organic, and resolute at the same time. We’ve tested many DACs & AMPs here on Headfonia but only a handful, maybe less than a handful managed to provide an organic timbre with this level of transparency. On top of that, the PRaT felt fast, agile, and snappy with good authority. The whole spectrum feels dynamic and coherent, especially if you combine it with an equally capable IEM. It handles congestion better than 90% of DACs & AMPs that I’ve tested in the past and handles complex passages with multiple instruments quite well. Let’s dissect the major bands into a few paragraphs and take a closer look.

Low

The lows of the K9 Pro ESS are a perfect dance balance between quantity and quality. Depending on the pairing, the unit is capable of delivering some of the most impactful lows I’ve heard throughout the years. Sub-bass presence is ample, the bass hits quick, recuperates fast and it has no problem keeping up with a speedy twin-pedal passage. The mid-bass is controlled and never bleeds over. The K9 Pro ESS delivers punchy bass with great texture. The note-weight is excellent, and the resolution is astounding. Even my Etymotics are in awe. They weren’t sure they were capable of delivering such bass. 

Mid

The midrange of the K9 Pro ESS is musical, dynamic and of course, very clean. The vocals are articulate and vivid with plenty of details and microdynamics. You can hear even the smallest details of out-of-focus instruments. The signature feels organic and accurate, the instruments, especially guitars and mid-dependant natural instruments have this realistic timbre that we audiophiles are on the lookout for. They do not feel artificial or clinical and the note weight is just accurate. The upper midrange offer ample energy with marvelous resolution and is very controlled just like the rest of the spectrum. Hi-hats and crashes extend quite well and the decay, as well as the attack feels snappy.

High

I find K9 Pro ESS’s whole response quite successful but treble is where I find myself drawn every time I turn on the FiiO’s latest bag of tricks. The whole treble region is detailed, resolving, transparent and clean. The extension is impressive and this may be the best treble response I heard from a sub 1.5k$ AIO device. The highs extend above the headroom, resulting in enhanced perception of air and spaciousness of the presentation. The treble performance damn impressive. It is really hard to find any downsides to it, perhaps if you are using an overly bright IEM or HPs then you may find it a tad harsh but that will be the case with majority of highly resolving DAC & AMPs out there.

Page 1: FiiO, K9 Pro ESS, Specs & Highlights, Packaging & Accessories, Design & Build

Page 2: Technology & Audio Circuitry, Controls & Operation

Page 4: Power, Technical Capability, Comparisons, Conclusion