Closer Examination

Tell you what—the FiiO K9 Pro ESS makes the K5 Pro ESS seem like a toy even though it is a desktop class DAC/amp, too! The K9 Pro ESS is a newer version of the AKM-based K9 Pro that itself is still a relatively new product. However, the AKM factory fire changed everything to where this is the third FiiO product I have reviewed that has had an ESS update. There are some additional changes, which we will talk about over the course of this review, but for all intents and purposes, the two can be considered equivalent in function and form. This version measures 20 x 22.5 x 7.2 cm and weighs ~2.7 kg, with an anodized black and sandblasted aluminium alloy chassis that looks and feels great in hand. It has a similar design language as the K5 Pro ESS, but with straight sides and chamfers on the corners instead of the curved corners there.

On the front, a clear Pro moniker confirms this is the FiiO K9, and the headphone connectors are on the left with FiiO offering two balanced outputs: a full-sized XLR (behind a cover piece) and a 4.4 mm port with a single-ended 1/4" (6.35 mm) jack alongside. These are labeled accordingly, although subtly against the darker base to where the physical differences between the three are the best way to distinguish them. In the center is a large aluminium alloy volume knob with a smooth PVD finish in gold on the side, which is different from the subtler monochrome knob on the older K9 Pro. An indicator dot shows the volume level, with "min" and "max" written underneath to mark the two end points. I can't say I like the glossy knob much. I would have rather seen a more solid-feeling knurled aluminium knob instead, although I appreciate the indicator lightning ring associated with the knob as with the K5 Pro ESS.


That subtle labeling used elsewhere on the front continues on the right side, which can be a real issue given identifying what is what in general use isn't easy. On the top are five small indicator LEDs that mark the current input type, and you might as well memorize the lineup. The bottom is arguably worse with two sets of matching sliders and buttons, of which the first two are 3-way sliders and the next two press-in buttons. From left to right, we get an output selector for the FiiO K9 Pro ESS to solely be a DAC, a preamp should you want to use line out with, say, active speakers, or a full-fledged DAC/amplifier with headphone outputs. Next up is a gain selector for low, medium, and high gain, an input selector toggle button that works with the five indicator lights placed above, and a power/standby button that is quite handy for when you don't want to reach behind the back to physically cut power off the unit. Power consumption in standby mode is a trickle at best—under 2 W as measured.


A look from the top head-on somewhat justifies the gold coating on the volume knob with the similarly colored Hi-Res Audio and THX certificates printed right above. Further up is the FiiO logo in the same off-white engraving plaguing the front, although it is large enough and works well here as it isn't obnoxious branding, either. We then get to the sides where more changes from the K9 Pro are the heat-dissipation vents on either side because of the more power-hungry DAC implementation, amplifier stage, and integrated power supply. A Type-C USB input on the right side means mobile devices are more easily connected to the K9 Pro ESS, but the presence of these vents has the horizontal orientation yield better thermal performance.


The vents give us a sneak preview of the hardware inside, although this angle naturally leads to the bottom where you would place the rubber feet that lift the K9 Pro ESS off the desk to prevent scratches to the surface and dampen any vibrations moving either way. There are no marks, so you might place them slightly askew to match the volume knob engineered ~1° off on purpose. In addition to all the certification information on the bottom, we see the red voltage selector switch you absolutely need to set correctly. It was already set to 230 V on this UK SKU, and switching between 110 or 230 V doesn't require tools.


The back is filled with I/O options galore. The very edges have multiple Phillips-head screws in a countersunk fashion to keep the finish clean. The internal power supply means the left side has the AC power inlet with a dedicated power switch below, and a replacement for the fuse between the two for OVP and OCP is included in the box. The K9 Pro ESS takes a maximum of 150 mA on 220–230 V (300 mA on 110–115 V), which corresponds to ~33 W intake at most, but is far less most of the time—certainly not a power hungry Class-A amplifier. The K9 Pro ESS also makes a strong case for itself with input options beyond just USB, but there are two different USB inputs even so. There are digital and analog inputs, with the former having coax and optical in addition to Bluetooth LE, where the provided antenna screws in for a stronger signal. Then there's a whole analog section for the other sources, such as streamers and phono stages or even other DACs, with a 4.4 mm in or line in to use the K9 Pro ESS as just a DAC or preamp courtesy the single-ended line out or balanced 3-pin dual XLR line out.